DTC C0279. GMC Truck Yukon

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2004 🢒 Yukon - 4WD 🢒 DTC 🢒 DTC C0279

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.

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.

The PCM must have the correct part number for the specified application.

Step	Action	Yes	No
1	Did you perform the ABS Diagnostic System Check?	Go to Step 2	Go to Diagnostic System Check - ABS
2	Use a scan tool in order to clear the DTCs. Turn OFF the ignition for 5 seconds. Turn ON the ignition and wait 10 seconds. Does the DTC set?	Go to Step 3	Go to Diagnostics Aids
3	Verify the correct 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	Important: Perform the set up procedure for the PCM. Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls - 4.8L, 5.3L, and 6.0L. Did you complete the replacement?	Go to Step 7	--
7	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 3	System OK

DTC C0279 W/JL4

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 VSES event. Power and ground are both switched ON by the EBCM to energize the precharge pump motor.

Conditions for Running the DTC

•	The ignition is ON.

•	The precharge pump is activated during a VSES or 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:

•	Testing for Electrical Intermittents

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

•	Connector Repairs

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

Schematic Reference: Antilock Brake System Schematics

Connector End View Reference: Antilock Brake System Connector End Views

Did you perform the ABS Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - ABS

Use the scan tool to clear the DTCs.
Turn OFF the ignition for 5 seconds.
Turn ON the ignition.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 3

Go to Diagnostic Aids

Turn OFF the ignition.
Disconnect the precharge pump motor harness connector.
Use a connector test adapter kit to connect a test lamp between the precharge pump motor circuits.
Turn ON the ignition.

Does the DTC reset?

Go to Step 9

Go to Step 4

With the test lamp still connected, select the VSES Special Functions menu on the scan tool.
Select and perform the Pre-Charge Bleed.

Does the test lamp illuminate and then turn OFF when the Pre-Charge Bleed is performed?

Go to Step 5

Go to Step 11

Important: Always ensure that the master cylinder reservoir cap is in place and secure before turning ON the precharge pump.

Reconnect the precharge pump motor harness connector.
Use the scan tool to perform the Pre-Charge Bleed.

Does the precharge pump motor run?

Go to Step 6

Go to Step 8

Observe the fluid in the master cylinder reservoir.
Use the scan tool to perform the Pre-Charge Bleed.

When the precharge pump runs, can fluid be seen discharging back into the master cylinder reservoir?

Go to Step 13

Go to Step 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

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

Important: Turn ON the ignition when testing for a short to voltage.

Turn OFF the ignition.
Disconnect the EBCM harness connector.
Test the precharge pump motor circuits for the following.

•

An open

•	A short to ground

•	A short to voltage

•	Shorted together

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

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

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

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?

Go to Step 14

Go to Step 13

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.

Replace the EBCM. Refer to Electronic Brake Control Module Replacement .

Did you complete the replacement?

Go to Step 16

Replace the EBCM and the precharge pump assembly. Refer to Electronic Brake Control Module Replacement and Brake Pressure Modulator Valve Pre-Charge Pump Replacement .

Did you complete the replacements?

Go to Step 16

Replace the precharge pump assembly. Refer to Brake Pressure Modulator Valve Pre-Charge Pump Replacement .

Did you complete the replacement?

Go to Step 16

Use the scan tool Clear All Class 2 DTCs function to clear all of the DTCs from all modules.
Turn OFF the ignition for 5 seconds.
Turn ON the ignition.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

Go to Step 3

System OK