This code sets for a possible open in the internal EBCM pump motor relay circuit.
Action Taken When the DTC Sets
If equipped, the following actions occur
- The EBCM disables the ABS/Traction Control System (TCS)/Vehicle Stability Enhancement System (VSES) for the duration of the ignition cycle.
- The dynamic rear proportion (DRP) is degraded.
- The ABS indicator turns ON.
- The stability OFF indicator turns ON.
- The traction OFF indicator turns ON.
Conditions for Clearing the DTC
- The condition for the DTC is no longer present and the DTC is cleared with a scan tool.
- The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.
Diagnostic Aids
The pump motor is integral to the brake pressure modulator valve (BPMV). The pump motor is not serviceable.
Test Description
The number below refers to the step number on the diagnostic table.
- 5: Tests the ability of the EBCM to control the pump motor. If the test lamp illuminates, the pump motor circuit within the EBCM is good.
| Step | Action | 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 | Use the scan tool in order to clear the DTCs. Cycle the ignition to the OFF position. Start the engine. In park or neutral, release the brake. Turn OFF the engine. Does the DTC reset? | Go to Step 3 | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems |
| 3 | Remove the electronic brake control module (EBCM) from the brake pressure modulator valve (BPMV). Refer to Electronic Brake Control Module Replacement . Inspect the EBCM to BPMV connector for conditions which could cause an intermittent, such as damage, corrosion, poor terminal contact or presence of brake fluid. Is the connector OK and the cavity free of brake fluid? | Go to Step 5 | Go to Step 4 |
| 4 | If connector corrosion or damage is evident, replace BPMV and/or EBCM as necessary. If brake fluid is present, replace both BPMV and EBCM. Refer to Brake Pressure Modulator Valve (BPMV) Replacement and Control Module References in Computer/Integrating Systems for replacement, setup and programming. Did you complete the repair? | Go to Step 8 | |
| 5 | Connect the EBCM harness to the EBCM with the BPMV still separated. Connect a test lamp between the pump motor circuits, internal EBCM side, using the J 35616 GM Terminal Test Kit. See Special Tools . Cycle the ignition to the OFF position. Start the engine. In park or neutral, release the brake. Does the test lamp illuminate and then turn OFF? | Go to Step 7 | Go to Step 6 |
| 6 | Replace the EBCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup and programming. Did you complete the repair? | Go to Step 8 | |
| 7 | Replace the BPMV. Refer to Brake Pressure Modulator Valve (BPMV) Replacement . Did you complete the repair? | Go to Step 8 | |
| 8 | 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 |
DTC C0111-C0120
Circuit Description
An internal solenoid valve relay in the electronic brake control module (EBCM) supplies battery positive voltage to all solenoid valves. This voltage is referred to as system voltage. The EBCM activates the solenoid valve relay when the ignition is turned ON. Once the solenoid valve relay has been activated, The EBCM supplies ground to actuate individual solenoid valves.
DTC Descriptor
This diagnostic procedure supports the following DTC
DTC C0121 Valve Relay Circuit
Conditions for Running the DTC
- The ignition is ON.
- Ignition voltage is greater than 8 volts.
Conditions for Setting the DTC
One of the following conditions exists for 0.23 second
- The EBCM commands the solenoid valve relay on and battery voltage is less than 8 volts at the solenoid valves.
- An internal EBCM relay driver fault is not detected.
If equipped, the following actions occur
- The EBCM disables the Antilock Brake System (ABS).
- The ABS indicator turns ON.
- Dynamic rear proportion (DRP) function is degraded (w/NW7 or JL4).
- DRP function is disabled (w/o NW7).
- The red brake warning turns ON (w/o NW7).
- The EBCM disables Traction Control System (TCS).
- The EBCM disables Vehicle Stability Enhancement System (VSES).
- The condition for the DTC is no longer present and the DTC is cleared with a scan tool.
- The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.
The solenoid valve relay is integral to the EBCM. The relay is not serviceable.
The number below refers to the step number on the diagnostic table.
- 2: Determines whether the DTC is current.
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: ABS Schematics | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Use the scan tool in order to clear the DTCs. Cycle the ignition to the OFF position. Start the engine. In park or neutral, release the brake. Turn OFF the engine. Does the DTC reset? | Go to Step 3 | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems |
| 3 | Replace the electronic brake control module (EBCM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup and programming. Did you complete the repair? | Go to Step 4 | |
| 4 | Use the scan tool in order to clear the DTCs. Cycle the ignition to OFF and then ON. Does the DTC reset? | Go to Step 2 | System OK |
DTC C0121
The electronic brake control module (EBCM) uses an input from 2 brake fluid pressure sensors to enhance ABS braking and vehicle stability if equipped.
DTC Descriptors
This diagnostic procedure supports the following DTCs
- DTC C0131 Antilock Brake System (ABS) Pressure Circuit
- DTC C0136 Base Brake System Pressure Circuit/Sensor
- DTC C0138 Base Brake System Pressure Circuit/Sensor Low
- DTC C0139 Base Brake System Pressure Circuit/Sensor High