DTC C0279 W/O JL4
Circuit Description
The PCM sends engine/axle/tire IDs to the EBCM via serial data communications immediately after the modules are powered up.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C0279 Powertrain Configuration Not Valid
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
The EBCM receives invalid information from the PCM.
Action Taken When the DTC Sets
If equipped, the following actions occur:
| • | The EBCM disables the TCS. |
| • | The traction off indicator turns ON. |
Conditions for Clearing the DTC
The conditions for setting the DTC are no longer present and you use the scan tool Clear DTCs function.
Diagnostic Aids
Diagnose other ABS or TCS related DTCs prior to diagnosing DTC C0279.
If multiple TCS related DTCs are set, or the vehicle being serviced is not equipped with TCS, verify the correct EBCM is installed in the vehicle.
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 |
Does the DTC set? | Go to Step 3 | Go to Diagnostics Aids |
Verify the correct powertrain control module (PCM) is installed in the vehicle. Does the vehicle have the correct PCM? | Go to Step 4 | Go to Step 6 | |
4 | Use the scan tool in order to read the Calibration IDs of the PCM. Are the PCM Calibration IDs correct? | Go to Diagnostics Aids | Go to Step 5 |
5 | Perform the set up procedure for the PCM. Refer to Service Programming System (SPS) in Programming. Did you complete the action? | Go to Step 7 | -- |
6 | Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 7 | -- |
7 |
Does the DTC reset? | Go to Step 3 | System OK |
DTC C0279 W/ JL4
Circuit Description
The electronic brake control module (EBCM) uses the precharge pump in conjunction with the ABS pump to build hydraulic pressure for brake application during a vehicle stability enhancement system (VSES) event. Power and ground are both switched ON by the EBCM to energize the precharge pump motor.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C0279 Pre-charge Pump Circuit Performance
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The precharge pump is activated during a VSES or traction control system (TCS) event or when the EBCM performs the power-up self-test. Refer to ABS Description and Operation for a complete description of the power-up self-test. |
Conditions for Setting the DTC
| • | The EBCM detects open precharge pump circuitry. |
| • | The EBCM detects shorted precharge pump circuitry. |
| • | The master cylinder pressure sensor signal does not increase sufficiently during a pressure-build event. |
Action Taken When the DTC Sets
| • | The EBCM disables the VSES. |
| • | The TCS operates with engine torque reduction only. |
Conditions for Clearing the DTC
The conditions for setting the DTC are no longer present and you use the scan tool Clear DTCs function.
Diagnostic Aids
Thoroughly inspect connections or circuitry that may cause an intermittent malfunction. Refer to the following:
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests if the EBCM is detecting open or shorted precharge pump motor circuitry.
-
This step tests if the EBCM is capable of energizing the precharge pump motor.
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 in Vehicle DTC Information | ||||||||
2 |
Does the DTC reset? | -- | Go to Step 3 | Go to Diagnostic Aids | ||||||||
Does the DTC reset? | -- | Go to Step 9 | Go to Step 4 | |||||||||
Does the test lamp illuminate and then turn OFF when the Pre-Charge Bleed is performed? | -- | Go to Step 5 | Go to Step 11 | |||||||||
5 |
Important: Always ensure that the master cylinder reservoir cap is in place and secure before turning ON the precharge pump.
Does the precharge pump motor run? | -- | Go to Step 6 | Go to Step 8 | ||||||||
6 |
When the precharge pump runs, can fluid be seen discharging back into the master cylinder reservoir? | -- | Go to Step 13 | Go to Step 7 | ||||||||
7 | Inspect the master cylinder reservoir, the brake fluid supply hose to the precharge pump inlet and the precharge pump inlet port for any restriction that may cause the loss of fluid supply to the pump. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 15 | ||||||||
8 | Inspect for poor connections at the harness connectors of the precharge pump motor. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 15 | ||||||||
9 |
Important: Turn ON the ignition when testing for a short to voltage.
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 10 | ||||||||
10 | Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 13 | ||||||||
11 | Use a DMM to measure the resistance value of the precharge pump motor. Does the resistance measure within the specified range? | 0.3-1.0 ohms | Go to Step 12 | Go to Step 14 | ||||||||
12 | Use the DMM to measure the resistance between the high side of the precharge pump motor and a good ground. Does the resistance measure less than the specified value? | OL | Go to Step 14 | Go to Step 13 | ||||||||
13 | 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 16 | -- | ||||||||
14 |
Important: Following EBCM replacement, perform the set-up procedure for the EBCM and perform the Yaw Rate Reference Table Reset Procedure. Use the scan tool to perform the Tire Size Calibration procedure.
Did you complete the replacements? | -- | Go to Step 16 | -- | ||||||||
15 | Replace the precharge pump assembly. Refer to Brake Pressure Modulator Valve Pre-Charge Pump Replacement . Did you complete the replacement? | -- | Go to Step 16 | -- | ||||||||
16 |
Does the DTC reset? | -- | Go to Step 3 | System OK | ||||||||
