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Home >> GMC >> 2002 >> C3500 HD 6.5 F, Standard >> Repair and Diagnosis >> Brakes >> Mechanical - Hydraulic >> Hydraulic Brakes >> Diagnostic Information and Procedures >> Brake Warning Indicator Inoperative (Without DRLs) >> Test Description

Test Description

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

  1. 11:  This step tests for an open in the ABS pressure differential sensor signal circuit or the brake warning indicator control circuit by substituting the brake warning indicator lamp and the IPC with a test lamp.
Brake Warning Indicator Inoperative (Without DRLs)

Step Action Yes No
Schematic Reference:  Brake Warning System Schematics  
1 Did you review the Brake Warning System Description and Operation and perform the necessary inspections? Go to Step 2  Go to Symptoms - Hydraulic Brakes 
2 Verify a fault is present.
Does the brake warning indicator function normally?		 Go to TESTING FOR INTERMITTENT AND POOR CONNECTIONS in Wiring Systems Go to Step 3 
3
  1. Turn OFF the ignition for 5 seconds.
  2. Turn ON the ignition while observing the brake warning indicator.
Does the brake warning indicator illuminate for 3 seconds and then turn OFF?		 Go to Step 5  Go to Step 4 
4
  1. Install a scan tool.
  2. Select the 4WAL 3 Sensor Current Diagnostic Trouble Code(s) function on the scan tool.
Does the scan tool display DTC C0288?		 Go to DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION in Antilock Brakes Go to Step 10 
5 Apply the park brake.
Does the brake warning indicator illuminate?		 Go to Step 16  Go to Step 6 
6
  1. Disconnect the park brake warning switch harness connector. Refer to Park Brake Warning Lamp Switch Replacement in Park Brake.
  2. Connect a jumper wire between the park brake warning switch harness connector and a good ground.
Does the brake warning indicator illuminate?		 Go to Step 8  Go to Step 7 
7 Repair the open in the brake warning indicator control circuit. Refer to WIRING REPAIRS in Wiring Systems.
Did you complete the repair?		 Go to Step 23  -
8 Inspect for poor connections at the harness connector of the park brake warning switch. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS in Wiring Systems.
Did you find and correct the condition?		 Go to Step 23  Go to Step 9 
9 Replace the park brake warning switch. Refer to Park Brake Warning Lamp Switch Replacement in Park Brake.
Did you complete the replacement?		 Go to Step 23  -
10
  1. Turn OFF the ignition.
  2. Disconnect the EBCM 10-way harness connector.
  3. Connect a jumper wire between the ABS pressure differential sensor signal circuit and a good ground.
  4. Turn ON the ignition.
Does the brake warning indicator illuminate?		 Go to Step 21  Go to Step 11 
11 
  1. Turn OFF the ignition.
  2. Reconnect the EBCM 10-way harness connector.
  3. Remove the instrument panel cluster.
  4. Connect a test lamp between the battery positive voltage circuit and the brake warning indicator control circuit at the instrument panel cluster (IPC) harness connector.
  5. Turn ON the ignition.
Does the test lamp illuminate for 3 seconds and then turn OFF?		 Go to Step 13  Go to Step 12 
12 Repair the open in the brake warning indicator control circuit or the ABS pressure differential sensor signal circuit. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems.
Did you complete the repair?		 Go to Step 23  -
13 Inspect the brake warning indicator lamp for an open (burned out) filament.
Did you find and correct the condition?		 Go to Step 23  Go to Step 14 
14 Inspect for poor connections at the harness connector of the IPC. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS in Wiring Systems.
Did you find and correct the condition?		 Go to Step 23  Go to Step 15 
15 Replace the instrument panel cluster.
Did you complete the replacement?		 Go to Step 23  -
16
  1. Disconnect the differential pressure switch harness connector. Refer to Combination Valve Replacement .
  2. Connect a jumper wire between the ABS pressure differential sensor signal circuit and a good ground.
Does the brake warning indicator illuminate?		 Go to Step 18  Go to Step 17 
17 Repair the open in the ABS pressure differential sensor signal circuit. Refer to WIRING REPAIRS in Wiring Systems.
Did you complete the repair?		 Go to Step 23  -
18 Test the ground circuit of the brake pressure differential switch for an open. Refer to CIRCUIT TESTING and WIRING REPAIRS in Wiring Systems.
Did you find and correct the condition?		 Go to Step 23  Go to Step 19 
19 Inspect for poor connections at the harness connector of the brake pressure differential switch. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS in Wiring Systems.
Did you find and correct the condition?		 Go to Step 23  Go to Step 20 
20 Replace the brake pressure differential switch. Refer to Combination Valve Replacement .
Did you complete the replacement?		 Go to Step 23  -
21 Inspect for poor connections at the harness connector of the EBCM. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and CONNECTOR REPAIRS in Wiring Systems.
Did you find and correct the condition?		 Go to Step 23  Go to Step 22 
22 Replace the EBCM. Refer to ELECTRONIC BRAKE CONTROL MODULE (EBCM) REPLACEMENT in Antilock Brake System.
IMPORTANT: Following EBCM replacement, use the scan tool to perform the Tire Size Calibration procedure.

Did you complete the replacement?		 Go to Step 23  -
23 Verify the system is repaired.
Does the brake warning indicator function normally?		 System OK Go to Step 3 
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