Normal Operation and Fault Conditions

On vehicles equipped with a 3.5L or a 3.7L engine, the TCM in an internal part of the PCM. With the ignition ON, the PCM sends messages to the ABS module over the HS-CAN. If the ABS module does not receive these messages within the specified time frame, the ABS module sets DTCs. This can be due to a PCM failure, a circuit failure on the HS-CAN or an excessive load on the network.

The CCM is an internal component of the PCM. With the ignition ON, the PCM sends messages to the ABS module through the BCM over the HS-CAN. If the ABS module does not receive these messages within the specified time frame, the module sets a DTC. This can be due to a PCM failure, a circuit failure on the HS-CAN or an excessive load on the network. For information on the messages sent to the ABS module by the PCM, refer to the NETWORK MESSAGE CHART .

The stoplamp switch (also known as the brake pedal switch, BPP switch and BOO switch) contains 2 sets of contacts, one set for a voltage signal and the other set for a ground signal.

For the voltage signal input, the stoplamp switch receives voltage at all times from the BCM. When the brake pedal is applied, the normally open switch closes and routes voltage to the BCM and the PCM.

For the ground signal input, the stoplamp switch receives a voltage signal from the PCM. The voltage signal is routed to ground through the normally closed switch. When the brake pedal is applied, the normally closed switch opens, interrupting the voltage signal from the PCM.

When the PCM receives these inputs it sends a message on the HS-CAN to the ABS module and other modules.

PPT I ABS MODULE DTC FAULT TRIGGER CONDITIONS

DTC	Description	Fault Trigger Condition
P1571:64	Brake Switch: Signal Plausibility Failure	Sets when the ABS module receives a brake pedal switch message and other module inputs disagree or the ABS module does not receive a brake pedal switch message and other module input indicates vehicle braking.
U0100:00	Lost Communication With ECM/PCM "A": No Sub Type Information	Sets when the ABS module does not receive any messages from the PCM.
U0100:87	Lost Communication With ECM/PCM "A": Missing Message	Sets when the ABS module detects any of the following messages is missing: accelerator pedal position, brake pedal position, brake on-off switch, cruise control status or engine rpm.
U0101:00	Lost Communication With TCM: No Sub Type Information	Sets when the ABS module does not receive any transmission messages from the PCM.
U0101:87	Lost Communication With TCM: Missing Message	Sets when the ABS module detects the transmission gear position or transmission gear lever (PRNDL) position message is missing.
U0104:00	Lost Communication With Cruise Control Module: No Sub Type Information	Sets when the ABS module does not receive any cruise control messages from the PCM.
U0104:87	Lost Communication With Cruise Control Module: Missing Message	Sets when the ABS module detects any of the following cruise control messages are missing: adaptive cruise control status, adaptive cruise control deceleration request, adaptive cruise control precharge request, collision mitigation by braking status, collision mitigation by braking deceleration request, collision mitigation by braking precharge request.
U0401:68	Invalid Data Received From ECM/PCM "A": Event Information	Sets when the ABS module detects any of the following message is "invalid" instead of the actual information: accelerator pedal position, brake pedal position, brake on-off switch, cruise control status or engine rpm.
U0401:82	Invalid Data Received From ECM/PCM "A": Alive/Sequence Counter Incorrect/Not Updated	Sets when the ABS module detects the cruise control status counter message does not increase following a cruise control event.
U0402:68	Invalid Data Received From TCM: Event Information	Sets when the ABS module detects the transmission gear position or transmission gear lever (PRNDL) position message is "invalid" instead of the actual gear or gear lever position.
U0405:66	Invalid Data Received From Cruise Control Module: Signal Has Too Many Transitions/Events	Sets when the ABS module detects the collision mitigation requests from the PCM are either too numerous or too long.
U0405:68	Invalid Data Received From Cruise Control Module: Event Information	Sets when the ABS module receives an invalid collision mitigation by braking pre-charge request from the PCM.
U0405:81	Invalid Data Received From Cruise Control Module: Invalid Serial Data Received	Sets when the ABS module detects the adaptive cruise control deceleration requests from the PCM are either too numerous or too long. This DTC also sets if the speed difference while braking exceeds a predetermined threshold.