Possible Causes

BT1: 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 BT2.	DIAGNOSE the scan tool does not communicate with the ABS module. REFER to COMMUNICATIONS NETWORK

BT2: 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 BT3.	DIAGNOSE the scan tool does not communicate with the GWM. REFER to COMMUNICATIONS NETWORK .

BT3: CHECK FOR ABS MODULE DTCS

Are any DTCs present?

Yes	No
DIAGNOSE the ABS module DTC. REFER to the ABS - ANTILOCK BRAKING SYSTEM DTC INDEX	Go to BT4.

BT4: CHECK FOR GWM DTCS

Are any DTCs present?

Yes	No
DIAGNOSE the GWM DTC. REFER to COMMUNICATIONS NETWORK	Go to BT5

BT5: CHECK FOR PCM DTCS

Are any DTCs present?

Yes	No
DIAGNOSE the PCM DTC. REFER to the appropriate Electronic Engine Controls article.	Go to BT6.

BT6: RECHECK FOR PCM DTCS

Yes	No
DIAGNOSE the PCM DTC. REFER to the appropriate Electronic Engine Controls article	Go to BT7.

BT7: CHECK THE TRACTION CONTROL SYSTEM

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 Electronic Engine Controls article	The system is operating correctly at this time. The concern may be caused by a loose or corroded connector.