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Technical difficulties on how I uploaded images. Please log in as member to view images until I can fix this. 1/27/17
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C0161 ABS Brake circuit malfunction per code reader via OBDII port (note: some autoparts stores only read "P" codes. Make sure they can read "C" codes as well). Stabilitrak, traction control error presented on DIC. Usually not a CEL on dash.
Physically noted failure features: Tail brake lights continuously on (they shut off when car is turned off -- ignition must be on to detect condition). Car can shift out of park without pressing brake pedal. Car not able to take out of park. This condition will disable cruise control and park assist.
For Acadia, Enclave Outlook Traverse.
Common fix is to replace and recalibrate Brake Pedal Position Sensor (BPPS). I believe most conditions do not require replacement at this point in the lifecycle of our vehicles, just a slight mechanical adjustment.
I had this failure on my 2009 Enclave around 110K intermittently until I corrected it this week at 116K at not cost. The stabilitrak/traction control first began appearing over rough roads and going up hill. Didn't occur for each drive cycle. Each time the car was turned off, the DIC would reset. Over time it became progressively worse.
Researched posts on the Lambda forums here where VWTodd replaced 4-5 BPPS's (outlookforum.net & acadiaforum.net). The first was installed by the dealer and potentially not calibrated. VW since has replaced 3-4 more himself. He' reported the failure at about 9-12 month increment. Odd There would be so many.
The theory is tolerance slop from the pedal to the BPPS increases over time with wear. That changes the set point (starting point) of the calibrated BPPS. So as our car would go up hill and/or ride rough roads, the BPPS set point (point at which pressing the brake pedal turns on the brake lights) was on the edge of calibration adjustment and would momentarily set off the c0161 from pedal play in our case. This makes the car think you are driving with one foot on the gas and the other on the brake simultaneously. Don't be surprised if you are asked the two footed driver question. Its in the GM troubleshooting process. If they put you down about it, go someplace else.
I measured ~ .015" of wear between the mating surfaces of the BPPS and brake pedal. That doesn't sound like much, but the BPPS fork does not turn that much either. The BPPS fork is glass filled plastic which sands down the cast brake pedal. The pedal wears faster than the BPPS plastic. As well as the wearing down at the pivot point of the cast brake pedal. I believe this accounts for folks replacing their BBPS wo calibration earning P0161 again so quickly.
My guess is when most folks have BPPS failure, its mechanical, not electrical. The BPPS is a variable resistor, potential, volume control type of device. I've located EBCM and BPPS troubleshooting guides posted below. After you read these procedures, you might as well buy the part for the $15-25 bucks if you think the switch has an electrical malfunction.
The first logical choice is to recalibrate and existing part in place. This requires someone with the GM tech II tool (for the earlier models) to recal. I called two local dealers for pricing. One was $120, the other $260 to install a new BPPS and recal. A local shop thought they could recalibrate if I brought the car in for ~$65. So it seems possible other devices like the Snap-on Solo, as someone reported, can calibrate the sensor.
I modified the mounting position on my BPPS where I guessed the slop due to wear and rotated the BPPS to account for it. I'm using my original factory installed 116k BPPS, but just rotated it. I don't know the chart profile of the calibration of the BPPS. I assume my sensor is still within cal to whatever table is required and I just readjusted the start point so it works correctly again.
The below modification will save you about $120 and a trip to a shop w a calibration tool.
The BPPS sensor for my 2009 is p/n 25913321 (see first picture below). You'll have to check if this part number is valid for your year if you decided to replace. I did not replace this new part. I bought it before I got into the project.
The second picture shows the part in position on the brake pedal assembly (Second picture, part had fatory green paint on it is the BPPS). Remove the connector. (Now view Third picture) My thumb is touching the 7mm bolt that must be removed and my finger is on the plastic boss. Note my boss is already modified and is noticeably smaller than the hole it fits into. My boss is already moved into its new position to allow my vehicle's brake lights to function properly. Yours should be an interference fit at this time (unmodified), filling the hole in the metal completely. Then pull off the sensor noting how the fork fits inside the pedal post before you do. (Note: I turned the key on (engine off), pressed the brake pedal until the tail brake lamps came on and measured (pedal to floor distance) ~ 1/4"' Do this before you remove the sensor. Keep in mind, mine was not a hard failure. It was intermittent. So my brake lights were not always on. If your brakes are on already, try pulling the pedal up while watching the BPPS forks move below to get an idea of the slop you'll need to remove.)
Technical difficulties on how I uploaded images. Please log in as member to view images until I can fix this. 1/27/17
******************************
C0161 ABS Brake circuit malfunction per code reader via OBDII port (note: some autoparts stores only read "P" codes. Make sure they can read "C" codes as well). Stabilitrak, traction control error presented on DIC. Usually not a CEL on dash.
Physically noted failure features: Tail brake lights continuously on (they shut off when car is turned off -- ignition must be on to detect condition). Car can shift out of park without pressing brake pedal. Car not able to take out of park. This condition will disable cruise control and park assist.
For Acadia, Enclave Outlook Traverse.
Common fix is to replace and recalibrate Brake Pedal Position Sensor (BPPS). I believe most conditions do not require replacement at this point in the lifecycle of our vehicles, just a slight mechanical adjustment.
I had this failure on my 2009 Enclave around 110K intermittently until I corrected it this week at 116K at not cost. The stabilitrak/traction control first began appearing over rough roads and going up hill. Didn't occur for each drive cycle. Each time the car was turned off, the DIC would reset. Over time it became progressively worse.
Researched posts on the Lambda forums here where VWTodd replaced 4-5 BPPS's (outlookforum.net & acadiaforum.net). The first was installed by the dealer and potentially not calibrated. VW since has replaced 3-4 more himself. He' reported the failure at about 9-12 month increment. Odd There would be so many.
The theory is tolerance slop from the pedal to the BPPS increases over time with wear. That changes the set point (starting point) of the calibrated BPPS. So as our car would go up hill and/or ride rough roads, the BPPS set point (point at which pressing the brake pedal turns on the brake lights) was on the edge of calibration adjustment and would momentarily set off the c0161 from pedal play in our case. This makes the car think you are driving with one foot on the gas and the other on the brake simultaneously. Don't be surprised if you are asked the two footed driver question. Its in the GM troubleshooting process. If they put you down about it, go someplace else.
I measured ~ .015" of wear between the mating surfaces of the BPPS and brake pedal. That doesn't sound like much, but the BPPS fork does not turn that much either. The BPPS fork is glass filled plastic which sands down the cast brake pedal. The pedal wears faster than the BPPS plastic. As well as the wearing down at the pivot point of the cast brake pedal. I believe this accounts for folks replacing their BBPS wo calibration earning P0161 again so quickly.
My guess is when most folks have BPPS failure, its mechanical, not electrical. The BPPS is a variable resistor, potential, volume control type of device. I've located EBCM and BPPS troubleshooting guides posted below. After you read these procedures, you might as well buy the part for the $15-25 bucks if you think the switch has an electrical malfunction.
The first logical choice is to recalibrate and existing part in place. This requires someone with the GM tech II tool (for the earlier models) to recal. I called two local dealers for pricing. One was $120, the other $260 to install a new BPPS and recal. A local shop thought they could recalibrate if I brought the car in for ~$65. So it seems possible other devices like the Snap-on Solo, as someone reported, can calibrate the sensor.
I modified the mounting position on my BPPS where I guessed the slop due to wear and rotated the BPPS to account for it. I'm using my original factory installed 116k BPPS, but just rotated it. I don't know the chart profile of the calibration of the BPPS. I assume my sensor is still within cal to whatever table is required and I just readjusted the start point so it works correctly again.
The below modification will save you about $120 and a trip to a shop w a calibration tool.
The BPPS sensor for my 2009 is p/n 25913321 (see first picture below). You'll have to check if this part number is valid for your year if you decided to replace. I did not replace this new part. I bought it before I got into the project.
The second picture shows the part in position on the brake pedal assembly (Second picture, part had fatory green paint on it is the BPPS). Remove the connector. (Now view Third picture) My thumb is touching the 7mm bolt that must be removed and my finger is on the plastic boss. Note my boss is already modified and is noticeably smaller than the hole it fits into. My boss is already moved into its new position to allow my vehicle's brake lights to function properly. Yours should be an interference fit at this time (unmodified), filling the hole in the metal completely. Then pull off the sensor noting how the fork fits inside the pedal post before you do. (Note: I turned the key on (engine off), pressed the brake pedal until the tail brake lamps came on and measured (pedal to floor distance) ~ 1/4"' Do this before you remove the sensor. Keep in mind, mine was not a hard failure. It was intermittent. So my brake lights were not always on. If your brakes are on already, try pulling the pedal up while watching the BPPS forks move below to get an idea of the slop you'll need to remove.)
Thank you for that insight. Of course there are several sensors which may generate the Stabilitrac / Traction control messages. This is one of the easiest possible fix and it is free.
