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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.

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.

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 and restrict 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.

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.

Also, if you encounter a Duramax with a blocked DPF [NS1] [AM2] or damage to the turbocharger due to high temperatures, you might need to educate the vehicle owner on avoiding extended idle times. While older diesel engines might have benefited from letting them idle for an extended period, newer diesel engines could clog the DPF,[NS3]  and the turbocharger might experience higher than average temperatures. Also, the driver may abort the regen process because it is inconvenient, or they fear the higher idle is rough on the engine. The reality is not performing the regen process could damage the new turbocharger.

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 “sharp” 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 manufacturer’s 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. That’s 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).

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).

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.

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.

One of the first items to be replaced on any Tesla model are the tires. This is due to tire wear from the instant torque of the electric motor. When replacing the tires, you will have to service the TPMS sensors.

Tesla has used Baolong (from 2012 to 2014), Continental (from 2014 to 2020 ) and a proprietary sensor that uses Bluetooth. For 2021, the Model Y started to use a sensor that communicates using Bluetooth protocols. Not much is known about the new system except that the sensors are currently available only through Tesla.

The Baolong TPMS system will not display the pressures on the center display. However, the Continental and Bluetooth systems will display the pressures for the driver. Tesla offers a retrofit kit to convert the Baolong system to a Continental system. The procedure involves replacing a module on the vehicle. Baolong sensors are available on the market, and aftermarket replacements can be programmed for the car.

Like many TPMS systems, the Tesla TPMS system has a built-in feature that automatically detects a new set of wheel sensors. The TPMS sensors can be reset via the vehicle’s touchscreen. The reset function is only possible when the vehicle is on. 

Before starting, set the tires to the correct cold tire inflation pressure according to the door placard and tire size. Before servicing the tires, make sure the system is functioning. 

Auto Learn

1. Turn the touchscreen on.
2. From the touchscreen, touch Controls > Settings > Service & Reset > Tire Pressure Monitor > Reset Sensors. Reset the sensors based on the wheel size.
   If a tire pressure warning displays, exit the vehicle, close the rear trunk and all the doors, wait for the touchscreen to go black, re-enter the car and ensure that the correct wheel size is selected before touching Reset.
3. Touch Reset, and then touch OK.
4. Press and hold one of the scroll wheels and select ‘Car Status’ to see an overview of the TPMS information. When the sensors are unknown, all the values will be shown as “- -”.
   Ensure that the vehicle is stationary for at least 20 minutes before continuing to the next step.
5. Perform a road test. Auto learning will start when the vehicle exceeds 25 mph. When auto-learning completes, the tire pressure information displays for all wheels and clears any TPMS faults. Note: Auto learning can take up to 20 minutes during a test drive.

Try this procedure again if “Tire Pressure System Needs Service” displays after performing auto-learning. If the warning still persists after 5 minutes of driving at 25 mph, further diagnostics might be required. This can include using a TPMS to verify the operation of the sensor.

Service Kits

Most Tesla models use service kits that have a clamp-on metal stem. A new service kit should be installed every time the tire is removed from the rim. The valve stem’s nut is a one-time-use item. Most kits are available in two finishes for silver and black rims. 

Replacement Sensors

There are a wide variety of programmable 433-megahertz sensors for Tesla models. There are also direct replacement options.

What is up with the foam?

Some original Tesla tires have a layer of foam attached to the inside. This foam is designed to absorb noise from the engine or transmission. If there is a puncture, you can still repair the tire. You can cut the foam away from the area of the tire and use a patch. Just replace the foam section using cement glue. 

1. Not cleaning the brake slides and hardware: Just slapping new pads and abutment clips where the old ones once resided never works. The caliper bracket slides need to be clean and free from rust. Don’t get overly aggressive with the wire brush. Some automakers are using anti-corrosion coatings and surface treatment on the brake caliper bracket lands. If brake cleaner and a nylon brush can’t tackle the deposits, you might be making the corrosion worse by using a wire wheel or file.  

2. Not lubricating the guide pins: This is a shortcut most pad slappers make. Caliper guide pins on floating calipers should always be cleaned in solvent and new grease should be applied. The grease is under extreme heat and pressure, so always use caliper-specific grease. NEVER put a torn boot back on a car. Failure to service the guide pins is the leading source of uneven pad wear. Also, avoid using impacts to remove or install the guide pins. Most guide pins are plated with an anti-corrosion material. Spinning the guide pin in a bore could damage the plating.

3. Installing the brake pads backwards: It happens more often than you would think! You may get a car in your shop with the owner complaining that the brakes are grinding after a “friend” changed the brake pads.

4. Not measuring the rotor: Rotor thickness and runout needs to be measured every time. Running a rotor that is below specifications can cause safety issues like cracking and fading. Also, not correcting lateral runout can lead to a pulsation complaint.

5. Not machining the rotor: New pads almost always require a fresh rotor surface so the pads can deposit a thin layer of friction material to increase braking performance. If old deposits of the previous material are on the rotor, it can contaminate the new pad and lead to performance and noise issues.

6. Not properly torquing the caliper bracket bolts: Not all caliper bracket bolts are the same. Torque ranges can vary from 30 to 110 ft./lbs. Also, some bracket bolts can be torque-to-yield or require liquid tread lockers. If you see an aluminum knuckle, look up the torque specifications.

7. Over torquing the caliper guide pin bolts: Caliper guide pin bolts typically need a 13 mm wrench to remove. It is a rookie mistake to go nuts on these bolts and break the heads off. Typically, these bolts require only 25 to 35 ft./lbs. of torque. Be gentle!

8. Installing a caliper upside down: Nothing is worse than going to bleed a new set of calipers on a vehicle, only to find the bleeders are on the bottom of the caliper and not the top. The bleeder needs to be at the top of the caliper to remove all the air. Always check the box to make sure you have a left and a right before you start the job.

9. Using cheap brake pads: The most common mistake for rookies is to shop for a pad on price and not quality, features and reputation.

10. Hanging the brake caliper by the hose: Nothing is more painful than to watch a brake caliper do a bungee jump from a control arm or knuckle and see it dangle by the brake hose. This can cause damage to the internal structure of the hose, which can cause a soft pedal or a rupture.