Test Description

WARNING: This page is about a different car, the 2005 Buick LaCrosse and 2005 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.

The number below refers to step number on the diagnostic table.

2: This step determines if the DTC is current.

DTC C0121

Step	Action	Value(s)	Yes	No
Schematic Reference: ABS Schematics Connector End View Reference: ABS Connector End Views
1	Did you perform the Diagnostic System Check - Vehicle?	-	Go to Step 2	Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2	Install a scan tool. Turn ON the ignition, with the engine OFF. Use the scan tool in order to clear the DTCs. Does the DTC reset?	-	Go to Step 3	Go to Diagnostic Aids
3	Connect the J 39700 Universal Pinout Box using the J 39700-530 Cable Adapter to the electronic brake control module (EBCM) harness connector only. See Special Tools . Test the battery positive voltage circuit for an open, high resistance, or a short to ground. Refer to Circuit Testing andWiring Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 5	Go to Step 4
4	Replace the EBCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement?	-	Go to Step 5	-
5	Use the scan tool in order to clear the DTCs. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text. Does the DTC reset?	-	Go to Step 2	System OK