A brake rotor absorbs and dissipates the heat energy generated by friction. How well the rotor can absorb and then release it into the surrounding air will determine the efficiency and capacity of the brakes.
The design of the rotor determines how it can handle the heat. On vented rotors, the thickness of the plates and how well air flows through the vanes helps to transfer heat to the surrounding air. Curved-vane designs on some vented rotors help to pull air through the center of the rotor to the outer edge and act as a pump. For curved vanes to work, they must be mounted on the hub in the correct direction, just as a directional tire must be mounted on the right wheel.
Slots cut into the face of the rotor have two functions. First, they provide leading edges for a better initial bite from the pad. Second, each groove provides a path for the gases being released by the pad. If the slots fill up with pad material, the brake system is operating at too high a temperature. Slots are radiused when milled to prevent stress in the rotor. Most slotted rotor manufacturers will not cut the slot to the edges of the rotor; doing so will compromise the strength of the rotor.
Holes drilled in the rotor can provide another path for the gases to escape from the pads and help with the initial bite of the pad. In some cases, the holes can reduce the weight of the rotor and improve cooling, as well. But there is a science to the holes, so the structure of the rotor is not compromised. Too many holes or holes near vanes can cause cracks. Also, the hole should have a chamfer to avoid creating a stress riser that can cause a crack.
The size of the brake rotor determines the rotor’s ability to generate brake force or torque. The best analogy is to try to turn a steering wheel using an inner spoke and then again using the outer wheel portion. The farther you move your hand out, the easier it is to turn the wheel.
Two-piece rotors included on some cars and in “big brake” kits have two advantages. First, two-piece rotors reduce rotational and unsprung mass. Second, the hat that is made of aluminum acts as a heat dam to prevent heat from being transferred to the hub, bearings and knuckle.
The most significant trend in rotors is using slots, holes and finishes on the hat and vanes to improve the cosmetics of the brake system.
While some of the aspects of Advanced Driver Assistance Systems – or ADAS – still seem like cutting edge technology found only in the world’s most advanced vehicles, the truth is that some of these systems have been around for decades, giving the promise of safer driving experiences to drivers all over the world.
Unfortunately, even though modern vehicles are equipped with increasingly advanced electronic safety systems, traffic fatalities have been on the rise since 2014, and while distracted driving may be a factor, we know that electronic safety systems are not able to offer the benefits they are capable of when vehicles are not maintained.
The performance of electronic safety systems is dependent on more components than you may realize. ABS wheel speed sensors and steering angle sensors provide real-time data that electronic safety systems depend on. ADAS related components like these from Standard are precision engineered and manufactured, and they’re also tested on real vehicles to ensure that they integrate seamlessly with the complex safety systems found in today’s modern cars.
Standard’s Collision Repair Program includes more than 8,000 of the hard-to-find, yet easily damaged parts that collision shops and repair facilities are looking for, including more than 900 ADAS-related components, such as park assist cameras, lane departure system cameras, and advanced sensors like blind spot detection sensors, cruise control, distance sensors, and park assist and steering angle sensors.
It’s the correct integration to the vehicle’s system that is so critical, so be sure your customers and your technicians understand programming and calibration requirements. For example, components like lane departure system cameras will generally require calibration after an installation but some components such as park assist sensors can just be installed on many vehicles without any programming necessary. So, if an ADAS component doesn’t seem to work correctly initially , it’s unlikely it’s a bad part. If you don’t perform the necessary calibration, the part isn’t defective, the installation was just never correctly completed.
Before replacing any ADAS component, it is important to refer to specific service information for the procedures required for that component. And before installing any replacement part after a collision, make certain that the mounting surface is true to the original location.
To ensure a complete and timely collision repair, Standard offers a wide range of award-winning in-person, live virtual and online learning classes to better educate technicians. You can do the work for your customer with the right parts and training from Standard.
Many AWD systems came onto the market in the 1990s. Unlike 4×4 truck systems of the day, these systems were always engaged. Many of the early systems used electro-mechanical ways to manage the distribution of power to the four wheels.
Most of these systems used viscous differentials and limited-slip differentials with special fluids inside. These components were prone to failure and are expensive to manufacture. The performance of these systems could also be challenging to control with sensors and actuators.
Around 2004, many manufacturers of AWD systems started to abandon complex transfer case center differentials in favor of less expensive clutches. Many vehicles were no longer equipped with limited-slip differentials. Instead, they were equipped with open differentials. Drivers never noticed the change or felt a loss in off-road or winter road capabilities. So, what happened?
Many of these AWD systems were able to utilize the brakes and sensors in the wheel ends to better control wheel slip. The basic principle is that with an open differential if you lock one side, the power transfers to the other side.
Transfer case designs were simplified and put the control in the clutches and planetary gears. These changes helped reduce cost while making the system more reliable.
The core controls for most AWD systems are the ABS, traction control and stability control (which uses the ABS brake modulator to control traction). The brake hydraulic control module on these vehicles has at least 12 valves. With these control channels, an AWD with open differentials can perform like it has limited-slip differentials. Passive or open differentials transfer the power to the wheel(s) that is spinning the fastest, or the wheel that is on the ring-gear side of the differential. These systems use the brake calipers to apply pressure to the spinning wheel and send power to the opposite side of the differential. This can evenly distribute the power to the rear or front axles under a variety of conditions.
The corrections are very fast pulsations of the brakes that are undetectable by the driver. If the car or truck is accelerating hard from a stop, the system will apply the brakes independently to prevent slipping. Even if the driver turns off the stability control, the brakes will manage the rear axle, so it performs like a limited-slip differential. If the vehicle is in snow or mud, it can control the traction with the brakes so the differential acts like it is locked.
TORQUE-VECTORING REAR DIFFERENTIALS
The torque-vectoring differentials can control the amount of power going to each wheel connected to the axle. Some high-horsepower FWD vehicles have a basic torque-vectoring differential (like the Ford Fiesta RS) to control torque steer.
Torque-vectoring differentials can work together with the stability control system and PCM to maximize traction during acceleration. It can be used during off-road and on-road situations at a wide range of speeds. The main inputs are the steering position sensor and yaw sensor. The differential control module makes corrections by determining where the driver wants to go and where the vehicle is going to make a correction.
This rear differential can control the power to the rear wheels. These differentials can act like a locking limited-slip or open differential with only a change of the electronically controlled clutches.
Torque-vectoring differentials have another advantage – they can disconnect a drive axle better than any locking hub. Decoupling an axle with clutch packs reduces rotating mass in the driveline and increases fuel mileage. The system will then decouple the center differential. On some vehicles, the driveshaft can be uncoupled from both the transmission and rear/front differential. This decoupling of the driveline can reduce rotating mass and load on the engine. This is all performed in milliseconds, and the driver does not feel even the slightest vibration.
SERVICE AND DIAGNOSTICS
Modern AWD systems need the foundation brake system and wheel bearing hubs with accurate wheel speed sensors to be in proper working order to function. This means that the pads and rotors must be able to produce enough friction to carry out the corrections. Issues with wheel bearings and seized calipers can result in less-than-optimal corrections.
Any leaks from the transmission, transfer case or differential should be taken seriously. Damage can occur if the fluid drops to a critical level. The most common leaks can be found around the driveshaft and axle seals.
Sometimes, there will be oil leakage at the seam between the automatic transmission and the transfer case; it can occur around the entire seam. If droplets can be seen, seal the areas with black sealant in the vicinity of the propeller shaft to the front axle transmission. If the problem is a “sweating” leak, sealing must not be carried out, as this is a normal phenomenon inherent in the design of oil-filled systems. If there are any leaks in the differential transfer case, check the vents and breathers. The seals can leak and fail if the case is over pressurized.
The post AWD and ABS Services appeared first on Brake & Front End.
Some turbocharger failures on some GM Duramax 6.6 diesel engines from 2011-2017 are quick and catastrophic. It could start with smoke from the tailpipe or even a catalytic converter clogged with oil and debris. You may notice the engine is down on power. These are easy to diagnose.
Some turbocharger failures for these engines are less dramatic and might not require a replacement unit. Instead, they start with a code and a check engine light. These are typically caught by the engine management system when it senses the turbocharger is no longer producing the expected level of boost for a given engine speed or load.
2017 Duramax 6.6L turbo diesel engine.
No matter the symptoms or damaged parts, the root cause of the failure must be diagnosed and resolved.
The cause of the failure or drivability problem might be related to the oil supply required to lubricate and cool the turbocharger’s bearings. In rare cases, a piece of debris can damage the compressor or the exhaust turbine. The Vane Position Sensor can fail and not command the variable vanes in the turbine housing which control the speed of the turbine. Further to that, this variable geometry turbocharger contain an oil control solenoid that commands vane position, this too can fail and be a fault mode on this unit.
One of the most common codes for the Duramax is DTC P0299. The engine management system knows the expected level of boost pressure for a given condition. DTC P0299 indicates the boost pressure is below expectations. To set a P0299 code it requires multiple incidents over one or two key cycles. If you have a scan tool, you can access the freeze-frame information when code P0299 was set. A P0299 is not an automatic sign the turbocharger needs to be replaced. It is just a starting point for further inspection and diagnostics.
Mechanical failures of a turbocharger are usually related to the lubrication system. For the oil to cool and lubricate the turbo, it must flow. Restrictions in the oil feed or return lines can cause excessive heat along with shaft and bearing wear.
Oil restrictions are typically caused by carbon deposits in the lines and passages. When an engine stops turning, the oil flowing to the turbocharger stops. The oil inside the turbocharger might drain out of the center section through the return line. The remaining oil in the center section is heated to the point where it’s turned into carbon deposits. This process can happen even faster if the driver is using low-quality oil.
When the turbocharger bearings and shaft wear, the seals can leak oil into the turbine and compressor housings. This oil can clog the Diesel Particulate Filter andrestrict the flow of exhaust gases. This can cause low boost pressure and a P0299 code.
On the intake side, the air filter may fail due to excessive pressure differential that rips the filter media from the frame. The pressure differential is typically caused by a clogged air filter, so it is cheap insurance to replace the air filter when the turbocharger is replaced and highly recommended.
On the exhaust side, foreign objects can come from anything that can exit the exhaust port. If you deal with an engine failure with catastrophic damage, the turbocharger’s turbine and variable geometry vanes could be damaged.
For all diesel pickups made after 2007, the performance and fit of the turbocharger are critical for the operation of the Diesel Particulate Filter or DPF. In addition, any leaks in the exhaust system from the turbocharger to DPF will lead to codes and problems.
The DPF uses pressure sensors before and after the filter to measure restriction and determine when to perform a regeneration cycle. If the downpipe is leaking, the readings will not be accurate. In some cases, a code P2463 for excessive soot might be active. In other cases, the ECM will not run the regeneration cycle due to the plausibility of the reading from the two sensors. If you encounter one of these leaks, follow the procedures in TSB 15457 to align the downpipe and DPF. The method discussed involves removing the clamps, supporting the exhaust system, installing new gaskets and realigning the pipes.
As an extra quality check, perform a forced DPF regen cycle and check for any resulting codes.
There are several ways to protect a new turbocharger. The lines that supply and return from the oil pan should be replaced if available, or thoroughly flushed and cleaned to guarantee they are free and clear of any blockages inside. Before the engine is started, the turbocharger should be pre-lubricated with a large syringe in the oil supply line.
The most important thing is to educate the vehicle owner on proper maintenance and oil changes. Most OEMs have specific grades and certifications for vehicles with turbocharged engines. Using the least expensive or what is available at a gas station can damage the turbocharger.
The bottom line is this: before replacing the turbocharger on a Duramax engine, find the root cause of the failure. By taking the time to do this, you will avoid costly rework.
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Magnets in transmission pans and oil drain plugs help capture ferrous metals, but how do you know when debris is a sign of trouble? Andrew Markel explains the role of these magnets, what they collect, and how to determine if a transmission or engine issue may be developing. Learn key insights for better maintenance and diagnostics.
This video is sponsored by Auto Value and Bumper to Bumper.
The post Magnets and Drain Plugs appeared first on Brake & Front End.
The second-generation VW Touareg hit the road in 2011 and finished its production run in 2018. Aligning this Touareg is very similiar to the previous generation. Previous-generation Touareg models had uneven and rapid tire wear problems. The second generation is not known for this issue.
Precautions
The Touareg is not your typical vehicle to align. It has a stability control system that needs a recalibration of the steering angle sensor if the toe front or rear is adjusted.
On vehicles with air ride systems, lifting the vehicle for a repair requires that the vehicle lift mode must be activated. The vehicle lift mode switches the air suspension control off. This prevents readjusting of the air springs when the vehicle is lifted. Vehicle lift mode is automatically switched off at a speed above 3 mph.
Use the following procedure to deactivate the air suspension:
1. Switch on the electrical parking brake.
2. Switch on the ignition.
3. Press the LOCK button in the center console for 5 seconds.
The “Vehicle Lift Mode” is displayed in the instrument cluster and the indicator lamp in the LOCK button flashes.
Inspect the tires before alignment. According to VW, the tread depth difference may be no more than 2 mm on an axle. Also, the service information says a wheel alignment should not be done until the vehicle has been driven 1,000 to 2,000 km (621 to 1243 miles), since it takes this long for the coil springs to settle.
Front Suspension
At the front of the Touareg is a double wishbone with a tall knuckle. The suspension can have either air or coil springs. The lower control arm inboard mounts have factory-installed cam bolts to adjust the camber and caster. The front lower cam bolt adjusts camber and the rear bolt adjusts caster.
The most common failure on these models is the lower shock bushing. Upper control arm bolts are torque-to-yield with a torque spec of 50 Nm and a turn of 180 degrees.
Rear Suspension
The rear suspension is a multi-link setup with a large lower control arm. Toe is adjusted with the toe link and camber is adjusted using the cam bolt in the lower control arm.
If the rear tires have inner edge wear, inspect the bushings for damage. Most likely, the bushing that attaches the knuckle to the lower control arm is damaged.
Back in the day, a non-directional rotor finish was the method used to solve a common problem that occurred on bench brake lathes. If the crossfeed speed was too fast, the rotor became like a vinyl record, and the pads became the needle that followed the grooves in the record. This would cause a clicking noise as the pads moved in the caliper as it followed the concentric grooves.
The solution was to apply a non-directional finish. A non-directional finish breaks up the grooves cut by the lathe. These are typically cut with a rotating abrasive disc that moves across the face of the rotor. The finish looks like cross-hatch marks on a honed cylinder. In the 1970s and 1980s, the pages of Brake & Front End had ads for lathes accessories to apply a non-directional finish.
Why was it such a big deal? The reality was that the crossfeed on some lathes was set to what was used for drum brakes. The faster setting made more pronounced concentric grooves on brake rotors. Typically, the solution was to reduce the crossfeed speed to reduce the grooves. Also, many floating caliper designs were not great at holding the brake pads steady in the bracket.
Today, non-directional finishes on new brake rotors still serve the same purpose, but they also help in the bedding of some friction formulations.
The surface finish of a new or resurfaced rotor should meet OEM specifications for good braking performance, pedal feel and quiet operation. Brand-new OEM rotors and aftermarket rotors from a quality supplier typically have a surface finish that can vary from 15 to 80 microinches. Most brake experts say the best finish is 50 microinches or less, though a finish in the 60- to 80-microinch range is acceptable.
When a rotor is turned on a brake lathe with sharp bits (we emphasize the word âsharpâ because it is absolutely essential for a quality rotor finish) and a feed rate that is not too fast, the rotors will have a finish that meets these recommendations. Dull bits and fast feed rates tear chunks of metal from the rotor, instead of properly cutting it as they should.
If you turn your rotors with sharp bits and the proper feed rate and depth of cut, using a hone to apply a non-directional finish can help to reduce noise and shorten burnishing times.
As a final step, any rotor should be cleaned so metal debris, oil and anti-corrosion chemicals are removed from the braking surface. Not washing the rotors after they have been turned can leave a lot of junk on the surface that can embed in the pads and possibly cause braking issues, as well as noise when the rotors are installed.
NON-DIRECTIONAL FINISH TECHNIQUES
Non-directional rotor finishes can be applied in a number of ways. One way is by using an abrasive disc in a drill or a special rotor refinishing brush. As with the sanding block, you want to give each side about one minute of sanding while the rotor is rotating on the lathe. Also, follow the manufacturerâs recommendation for rotational speeds. Another method is to hold a pair of sanding blocks wrapped with 120-grit sandpaper firmly against both sides of the rotor for about one minute while it turns on the lathe.
Sanding knocks off the sharp peaks on the surface of the rotor and generally improves the surface finish by 15 to 20.
WHAT REALLY CAUSES NOISE
A non-directional finish can reduce initial break-in noise and help suppress noise for a while; however, brake noise can still occur if there are vibrations between the pads and rotors.
Brake squeal is caused by undampened high-frequency vibrations. When the brakes are applied, and the pads contact the rotors, tiny surface irregularities in the rotors act like speed bumps, causing the pads to jump and skip as they rub against the rotors. If the pads are not dampened by shims (external or internal) or are loose in the caliper mounts, they shake and vibrate and may produce an annoying high-pitched squeal.
The vibration of the pads against the rotors can also create harmonic vibrations in the rotors that cause them to ring like cymbals. Depending on the metallurgy of the rotors and the design of the cooling fins, some rotors may ring louder than others, regardless of the type of surface finish.
So, even if you do everything right, you can still end up with a noise problem if the pads or rotors themselves are inherently noisy. Switching to a different brand of brake pads or substituting a different type of friction material may be necessary to get rid of the noise.
A tip for reducing noise-producing vibrations is to apply a high-temperature brake lubricant to the backs of the pads and the points where the pads contact the caliper. Lubricating the caliper mounts, shims and bushings is also recommended to dampen vibrations here, as the lubricant acts as a cushion. It also helps the parts slide smoothly so the pads wear evenly (uneven pad wear is a classic symptom of a floating caliper that is sticking and not centering itself over the rotor).
The type of rotors used on the vehicle can also affect noise. Some grades of cast iron are quieter than others. Thatâs one of the reasons why composite rotors have been used on various vehicles over the years. Besides being lighter, composite rotors can also be quieter when the right grade of cast iron is used for the rotor disc. Replacing a composite rotor with a solid cast-iron rotor changes the harmonics and frequency of the brake system and may increase the risk of brake noise on some vehicles. Also, some low-price rotors may use a lower grade of cast iron that is noisier than the OEM rotors they replace.
While it’s common for a customer to bring us a vehicle with a single, specific complaint, we often find more than one problem when getting into the diagnosis of their original concern. The owner only knows one thing; they want the vehicle to run and operate properly. It’s our responsibility to identify and execute a complete repair and convey what that entails to the customer.
Case study 1: 4R75E
Today’s story begins with a 2006 Ford F-150 equipped with a 5.4L engine, 4R75E transmission, and 434,000 hard-use miles. The customer’s concern was simple: The overdrive light was flashing, there were hard shifts in every gear, and the transmission malfunction indicator was illuminated on the dash. The customer provided the following trouble codes to us: P0705 (transmission range sensor circuit fault), P0748 (pressure control solenoid electrical), and P1702 (transmission range sensor circuit intermittent fault). He told us that the transmission had been rebuilt a year previously, and had never worked correctly since that time.
I began the evaluation by checking the fluid level and condition to see that it was full and fair. A quick code scan before the road test revealed that a lot more was going on with this vehicle beyond what the customer shared with us. A laundry list of engine performance codes was stored in memory along with the three that were provided by the customer. During the road test, I was able to confirm the hard shift in every gear complaint but also noted engine misfires present and a lack of power once warmed up. During the under-vehicle inspection, it appeared that the range sensor had been replaced at some point.
At this point I recommend electrical testing to pinpoint the cause of our range sensor and pressure control problems. Our service writer explained in detail that there was more than one issue on the vehicle and that it would take extra time to pin down properly. The customer approved the additional diagnostic time, so I rolled up my sleeves to dig into it.
I started with the range sensor codes. After checking power and ground down to the connection, range sensor voltages seemed normal but were out of sequence per the wiring schematic. TR2 should have had 12V present, but only showed 5V. TR3A, on the other hand showed 12V when it should have been 5V—very puzzling. I pulled the wiring loom off and discovered that the pigtail for the range sensor had been replaced as well. I removed the face of the connector and swapped pin 3 and pin 5. (See Figure 1, above).
Checking from the PCM connector down to the range sensor connector proved the wires were simply in the wrong position inside the connector. I cleared the codes, and the range sensor codes never came back during the road test, but I still had the hard shifts and overdrive light flashing. This meant it was time to move on to our apparent pressure control issue.
I began by disconnecting PCM connector C175T and checking for voltage on pins 38 (vref), 37 (ssb), 36 (tccs) and 39 (epc) with the key on. Pins 38, 37, and 36 all read battery voltage. When I got to pin 39, I found around 4V present. With that information in mind, I load-tested the wire from the transmission connector (pin 6) to the PCM (pin 39) to verify that I didn’t have a high resistance in the wire between the two. I suspected that the internal harness of the transmission had failed, but with the mileage of this vehicle, it was up to the customer to decide how further into this he wanted me to go.
Since the transmission had been rebuilt recently, the customer decided to have us replace the internal harness and pressure control solenoid before committing to a fully remanufactured transmission. After replacing the internal harness and EPC solenoid, the transmission worked perfectly, and the customer was pleased that we saved him the additional expense.
Case study 2: 4L80E
Our next vehicle was a 1999 Chevrolet Express 2500 equipped with a 5.7L engine, 4L80E transmission and 268,000 miles on the odometer. The customer’s concern was that the engine was stalling at stops and the transmission was shifting hard through its gears. The transmission had been rebuilt and started having problems eight months after that repair. The shop that had originally performed the transmission work attempted to diagnose these issues and had replaced multiple components before ultimately replacing the engine without solving the issue. Oops.
Upon starting the initial evaluation, I found the transmission fluid level low and in fair condition. A code scan revealed P0748 (pressure control solenoid electrical) stored. I pulled the vehicle into my bay to check for leaks before beginning a road test. As I pulled onto the lift and stopped, the engine chugged and stalled out. During the under-vehicle inspection, I found the transmission pan leaking. At this point, I stopped to talk with my service advisor because there was no leak concern noted by the customer. The advisor called the customer to confirm that he had been adding fluid to the van. I suspected that the stalling was caused by the low fluid condition present, so I topped off the transmission fluid and started another road-test. Even with the transmission fluid full the engine still wanted to stall when coming to a stop. When upshifting, the transmission shifted more firmly than it should with normal driving, but the shifts felt normal with heavy acceleration. The pressure control amperage on the scan tool seemed to be normal (around .7 to 1A, as seen in Figure 2).
Figure 2.
At this point it was clear to me that I may have more than one problem to diagnose on this vehicle. Our advisor got additional time approved, and I began my research.
Due to the hard shifting and P0748 code, I began by checking the circuit for the pressure control solenoid. When I inspected the PCM, I noticed that someone had spilled brake fluid on it when filling the master cylinder. I first checked the resistance in the circuit at the PCM C3 connector from pin 6 to pin 16 and found 4.5Ω, which is within specification. I then load-tested the wiring to make sure it could handle the current from the solenoid before putting my amp clamp on the circuit to prove what I already suspected. The current probe showed less than half an amp when our scan data showed around 1 amp. The pressure control solenoid was working properly, but the PCM had failed to control it properly. (See Figure 3).
Figure 3.
The customer was advised of our findings that the vehicle required a PCM replacement in order to correct the hard shifts, but that if the engine continued to stall, the transmission would also need to be replaced.
I replaced the PCM and that corrected the amperage issue to the EPC. (See Figure 4). Unfortunately, an internal transmission problem was evident after the PCM replacement, so we replaced the customer’s unit with our remanufactured transmission.
Figure 4.
After struggling with other shops to get the job done right, our customer was very happy to get the van back in working order except for one issue: now the headlights didn’t light up. After a few minutes of checking power and ground to the headlight connectors, we were able to confirm the sealed assemblies needed to be replaced, and the van was ready to get back to work.
You just finished a car or truck alignment or other repair that might have disconnected power to the vehicle. You pulled the vehicle off the lift and parked it in the lot. The customer pulls away and, within five minutes, they are back complaining an ABS, stability control or ADAS light is illuminated or a warning message is displayed. What happened?
When you scan for codes, you will find codes C1306, C1307 or another proprietary DTC indicating a malfunction with the steering angle sensor. Depending on the vehicle, these codes indicate a malfunction, inability to find the center or end stops, or missing calibration of the steering angle sensor.
Ninety percent of the time when a steering angle sensor code is active, it means the sensor needs to be calibrated. The other 10% of the time, the sensor has failed or there is an issue with the communication network sharing the data from the sensors.
The calibration process typically involves learning the center and end stops of the steering rack. Some systems require a static calibration in a bay with a scan tool attached. Others require a dynamic calibration which might need to be initiated with a scan tool. Other systems will perform the calibration automatically after a drive cycle.
If the calibration process can’t be completed, it will set a code for the steering angle sensor. Some proprietary codes will indicate why it aborted a steering angle sensor reset. If a code is not active, look at the datastream PIDs to see if the data changes when the steering wheel is moved.
If you are looking for the steering angle sensor data, it could be in several modules. Conventional systems connect the steering angle sensor to the ABS module, which is connected to a high-speed network like CAN. Vehicles with electric power steering typically have the sensors connected to the steering module that communicates with the engine control module to ensure engine speed does not drop when the driver turns the wheel. The steering module is connected to a CAN bus with the ABS and ECM. Another configuration might be to have a “sensor cluster” that communicates on the CAN network on its own.
The steering angle on your scan tool might be in degrees, but on some vehicles it could be a numerical value. Check the service information for the correct values. Most scan tools will have data from two steering angle sensors. Some vehicles will not use zero as the number for centered. Look at the service information. Also, some vehicles might require calibrating the motor position sensor that is located on the rack.
Engineers use two or three steering angle sensors in the column for redundancy and to double-check data. For some vehicles, the angle will have 180 degrees of difference. Other sensors that reveal data and codes are the yaw and lateral acceleration sensors. Dynamic-calibration vehicles will look at data from these sensors to confirm a change in steering angle results in a change in direction for the vehicle. If the sensor is not working or has active codes, a static or dynamic steering angle recalibration will not be possible.
On some vehicles, the steering sensor cluster is part of a module that may include functions for the turn signals, steering wheel, audio controls and wipers. This module is not a box, but part of the column and might have multiple CAN lines coming out of it. Often, the SAS cluster cannot be replaced on its own, instead requiring replacement of the entire unit.
ADAS CONNECTION
The steering angle is used by many ADAS functions, from blind-spot detection to autonomous driving. If the steering angle sensor is not calibrated, it could lead to the false activation of many ADAS systems. The most annoying malfunction is the false activation of the lane departure system. Even the smallest of errors in the SAS can make the vehicle think the driver is trying to steer into an oncoming lane. Some systems may just shake the seat, while other systems might try to steer the vehicle back into the lane.
