LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Cadillac >> 2007 >> STS V >> Repair and Diagnosis >> External Pages >> Different car >> Section 161 (Antilock Brake System, Traction Control System & Stability Control System) >> Diagnostic Information and Procedures >> DTC C0121 >> Test Description
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Test Description

WARNING: This page is about a different car, the 2007 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 2:  This step determines whether the DTC is current.
DTC C0121

Step Action Values Yes No
Schematic Reference: Antilock Brake System Schematics 
Connector End View Reference: Antilock Brake System Connector End Views 
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle
2 
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Use the scan tool in order to clear the DTCs.
  4. With the scan tool, perform the Automated Test.
Does the DTC reset as a current DTC?		 - Go to Step 3  Go to Testing for Intermittent Conditions and Poor Connections
3
  1. Disconnect the pump motor harness pigtail connector of the brake pedal modulator valve (BPMV).
  2. Measure the resistance between each pump motor control circuit and the housing of the BPMV at the pump motor harness pigtail connector of the BPMV.
Does the DMM display the specified value?		 OL Go to Step 5  Go to Step 4 
4 Replace the electronic brake control module (EBCM) and the BPMV. Refer to Control Module References for replacement, setup and programming and Brake Pressure Modulator Valve Replacement (CTS)  or Brake Pressure Modulator Valve Replacement (CTS-V) .
Did you complete the replacement?		 - Go to Step 6  -
5 Replace the EBCM. Refer to Control Module References for replacement, setup and programming.
Did you complete the replacement?		 - Go to Step 6  -
6
  1. Use the scan tool in order to clear the DTCs.
  2. With the scan tool, perform the Automated Test.
Does the DTC reset?		 - Go to Step 2  System OK
scientia non olet · About LEMON Manuals