Possible Causes

BU1: CHECK THE ABS MODULE COMMUNICATION

Ignition ON, engine OFF.
Press the Read Vehicle Information button to view the results of the modules communicating on the network.
Retrieve the continuous memory DTCs.
Does the ABS module pass the Network Test?

Yes	No
Go to BU3.	Go to BU2.

BU2: CHECK THE GWM COMMUNICATION

Review the results of the modules communicating on the network from the previous step.
Did the GWM pass the Network Test?

Yes	No
Go to BU3.	DIAGNOSE the scan tool does not communicate with the GWM. REFER to appropriate service information.

BU3: CHECK THE ABS MODULE FOR DTCS

Carry out the ABS self-test.

Yes	No
DIAGNOSE the ABS module DTCs. GO to the appropriate service information	Go to BU4.

BU4: CHECK FOR GWM DTCS

Carry out the GWM self-test.

Yes	No
DIAGNOSE the GWM DTC. REFER to appropriate service information	Go to BU5.

BU5: CHECK FOR PCM DTCS

Carry out the PCM KOEO self-test.

Yes	No
DIAGNOSE the PCM DTC. REFER to the appropriate service information	Go to BU6.

BU6: RECHECK FOR PCM DTCS

Yes	No
DIAGNOSE the PCM DTC. REFER to the appropriate service information	Go to BU7.

Test drive the vehicle.
- Carry out at least 1 ABS loose gravel acceleration and stop.
Ignition OFF.
Ignition ON, engine OFF.
Carry out the PCM KOEO self-test.
Are any DTCs present?

Yes	No
For KOEO DTC P1637, SET the ignition to OFF. DISCONNECT all PCM and ABS module electrical connectors. INSPECT the connectors for signs of corrosion, bent pins, pushed-out pins and spread terminals. REPAIR as necessary. For all others, DIAGNOSE the PCM DTC. REFER to the appropriate service information	The system is operating correctly at this time. The concern may be caused by a loose or corroded connector.