GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

IPC Ignition 1 Voltage

1

1

--

--

IPC Telltale Circuit Board Service Brake Soon Indicator Signal

1

1

1

--

1. Service Brake Soon Indicator Malfunction

Circuit/System Description

The electronic brake control module (EBCM) illuminates the instrument panel cluster (IPC) service brake soon indicator by applying ground to the lamp.

Diagnostic Aids

Thoroughly inspect connections or circuitry that may cause an intermittent malfunction.

Reference Information

Schematic Reference

Hydraulic Brake Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

ABS Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, use the scan tool IPC special function Lamp Test command On and OFF. Observe the IPC service brake soon indicator should turn ON for 3 seconds.

If the service brake soon indicator does not turn ON, go to circuit/system testing service brake soon indicator inoperative.
If the service brake soon indicator does not turn OFF, go to circuit/system testing service brake soon indicator always on.

Circuit/System Testing (Service Brake Soon Indicator Always ON)

  1. Ignition OFF, disconnect the EBCM harness terminal 39, Ignition ON, observe the service brake soon indicator illuminating.
  2. If the service brake soon lamp does not illuminate, test the ignition 1 circuit for an open/high resistance. If the circuit tests normal, test or replace the EBCM.
  3. Ignition OFF, disconnect from the IPC tell tale circuit board the harness connector containing the service brake soon indicator signal circuit.
  4. Ignition ON, Connect a 3A test lamp between the IPC IGN 1 voltage circuit terminal A12 and the service brake soon indicator signal circuit.
  5. If the test lamp does not illuminate , test the IPC IGN 1 voltage circuit terminal A12 circuit for a open/high resistance. If the circuit tests normal, test or replace the IPC tell tale circuit board.
    If the test lamp illuminates, test the brake indicator signal circuit for a short to ground. If the circuit tests normal, test or replace the EBCM.
  6. If all circuits test normal, test or replace the EBCM.

Circuit/System Testing (Service Brake Soon Indicator Inoperative)

  1. Ignition OFF, disconnect the EBCM harness serial data circuit terminal 39.
  2. Ignition ON, Connect a 3A fused jumper wire between the IPC service brake soon indicator signal circuit and ground. Observe the IPC service brake soon indicator.
  3. If the IPC service brake soon indicator illuminates, test or replace the EBCM.
  4. If the IPC service brake soon indicator does not illuminate, connect a test lamp between the IPC tell tale circuit board harness containing the service brake soon indicator signal circuit and the IGN 1 voltage circuit. Connect a 3A fused jumper wire between the EBCM service brake soon indicator signal circuit terminal 39 and ground. Observe the test lamp.
  5. If the test lamp illuminates, replace the IPC tell tale circuit board.
    If the test lamp does not illuminate, test for a short to voltage or open/high resistance in the service brake soon indicator signal circuit. If the circuit tests normal, replace the EBCM.
  6. If all circuits test normal, test or replace the EBCM.

Repair Instructions

    •  Telltale Circuit Board Replacement
    •  Control Module References for EBCM replacement, setup, and programming

Repair Verification

  1. Ignition OFF for 5 seconds, Ignition ON, observe the IPC service brake soon indicator.
  2. The IPC service brake soon indicator should illuminate for 3 seconds then turn OFF.
  3. Ignition ON, with the scan tool command the IPC Lamp Test ON and OFF.
  4. Service brake soon indicator should turn ON and OFF, if not check Circuit/System Testing.