Test Description

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers in the diagnostic table.

2: Lack of communication may be due to partial or total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
4: The symptom list in Symptoms will determine the correct diagnostic procedure to use.

Diagnostic System Check - Rear Wheel Steering

Step	Action	Yes	No
1	Install a scan tool. Does the scan tool power up?	Go to Step 2	Go to Scan Tool Does Not Power Up in Data Link Communications
2	Turn ON the ignition with the engine OFF. Use the scan tool in order to establish communication with the following modules: Automatic Transfer Case (ATC) Truck Body Control Module (TBC) Electronic Brake Control Module (EBCM) Instrument Panel Cluster (IPC) Powertrain Control Module (PCM) Rear Wheel Steering Control Module Sensing and Diagnostic Module (SDM) Does the scan tool communicate with all of the control modules listed above?	Go to Step 3	Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications
3	IMPORTANT: The engine may start during the following step. Turn OFF the engine as soon as you have observed the Crank power mode. Access the class 2 Power Mode in the Diagnostic Circuit Check on the scan tool. Rotate the ignition switch through all positions while observing the Ignition Switch Power Mode parameter. Does the Ignition Switch parameter reading match the ignition switch position for all switch positions?	Go to Step 4	Go toPower Mode Mismatch in Body Control System
4	Select the display DTCs function on the scan tool for the following control modules: Automatic Transfer Case (ATC) Truck Body Control Module (TBC) Electronic Brake Control Module (EBCM) Instrument Panel Cluster (IPC) Powertrain Control Module (PCM) Rear Wheel Steering Control Module Sensing and Diagnostic Module (SDM) Does the scan tool display any DTCs for the control modules listed above?	Go to Step 5	Go to Symptoms - Rear Wheel Steering System
5	Does the scan tool display any DTCs that begin with a "U"?	Go to Scan Tool Does Not Communicate with Class 2 Device in Data Link Communications	Go to Step 6
6	Does the scan tool display DTC B1000?	Go to Diagnostic Trouble Code (DTC) List in Body Control System	Go to Step 7
7	Does the scan tool display DTC B1367, P0562, P0563, P0621, P0615, P0622, P1637, P1638?	Go to Diagnostic Trouble Code (DTC) List in Engine Electrical	Go to Diagnostic Trouble Code (DTC) List