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Home >> Chevrolet >> 2004 >> Cutaway 4.8 V >> Repair and Diagnosis >> Brakes >> Antilock Brake System, Traction Control System & Stability Control System >> Diagnostic Information and Procedures >> DTC C0279 >> Test Description

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. 3:  This step tests if the EBCM is detecting open or shorted precharge pump motor circuitry.
  2. 4:  This step tests if the EBCM is capable of energizing the precharge pump motor.
DTC C0279

Step Action Values Yes No
Schematic Reference:  ABS Schematics  
Connector End View Reference:  ABS Connector End Views  
1 Did you perform the ABS Diagnostic System Check? - Go to Step 2  Go to Diagnostic System Check - ABS (W/O JL4) 
2
  1. Use the scan tool to clear the DTCs.
  2. Turn OFF the ignition for 5 seconds.
  3. Turn ON the ignition.
  4. 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
3 
  1. Turn OFF the ignition.
  2. Disconnect the precharge pump motor harness connector.
  3. Use a connector test adapter kit to connect a test lamp between the precharge pump motor circuits.
  4. Turn ON the ignition.
Does the DTC reset?		 - Go to Step 9  Go to Step 4 
4 
  1. With the test lamp still connected, select the VSES Special Functions menu on the scan tool.
  2. 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 
5
IMPORTANT: Always ensure that the master cylinder reservoir cap is in place and secure before turning ON the precharge pump.
  1. Reconnect the precharge pump motor harness connector.
  2. Use the scan tool to perform the Pre-Charge Bleed.
Does the precharge pump motor run?		 - Go to Step 6  Go to Step 8 
6
  1. Observe the fluid in the master cylinder reservoir.
  2. 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 
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.
  1. Turn OFF the ignition.
  2. Disconnect the electronic brake control module (EBCM) harness connector.
  3. 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 
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 Ω 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
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 (w/JL4)  or Electronic Brake Control Module Replacement (w/o JL4) .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.
Replace the EBCM and the precharge pump assembly. Refer to Electronic Brake Control Module Replacement (w/JL4)  or Electronic Brake Control Module Replacement (w/o JL4)  and Brake Pressure Modulator Valve Pre-Charge Pump Replacement .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
  1. Use the scan tool Clear All Class 2 DTCs function to clear all of the DTCs from all modules.
  2. Turn OFF the ignition for 5 seconds.
  3. Turn ON the ignition.
  4. 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
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