P106

Circuit Description

This diagnostic test functions on the assumption that a sudden decrease in non-drive (rear) wheel speed must be caused by a brake application. Non-drive wheel speed and stop lamp switch status are supplied to the PCM through serial data from the Electronic Brake and Traction Control Module (EBTCM). If there is a 2.5 mph or greater decrease of non-drive wheel speed in 0.2 second and a transition of the TCC or extended travel contacts of the TCC brake switch without a transition of the stop lamp brake switch the counter is incremented. When the counter reaches 5, Code P106 is set. The counter will be reset to zero if a transition of the Stop/BTSI/Cruise brake switch is noticed before the counter reaches 5.

Test Condition(s)

1. Codes P033, P090 and P137 not set.
2. Traction control and antilock brake systems are operating normally.
3. Non-drive wheel speed of 36 mph or greater;
OR
Non-drive wheel speed has been 36 mph or greater and has not fallen below 1.2 mph since.

Failure Condition(s)

1. A 2.5 mph or greater decrease in non-drive wheel speed in 0.2 second.
2. Transition in the TCC or extended travel contacts of the TCC brake switch.
3. No transition of the Stop/BTSI/Cruise brake switch noticed.
4. If conditions 1 through 3 are true, increment counter.
5. When counter reaches 5, set Code P106.

Action Taken

1. Traction control disabled.
2. PCM will set the Stop/BTSI/Cruise brake switch status to not applied.
3. 'TRACTION DISABLED' and 'REDUCED ENGINE POWER' message is displayed on the DIC.

Notes on Fault Tree

1. Checking if PCM input test PI89 will cycle when brake pedal is depressed and released. If PI89 remains 'HI', check for a short to voltage in the system. If PI89 remains 'LO', check for an open or short to ground in the system.
2. Checking for voltage supplied to the brake switch.
3. Checking CKT 540 for a short to ground.
4. Checking CKT 20 for a short to ground.
5. Checking CKT 20 for an open or for a bad PCM.