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.

DTC Descriptor

DTC C0901: Device 2 Voltage Low - EBCM

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

IGN I

C0901

C0901

--

--

Ground

--

C0901

--

--

Circuit/System Description

The electronic brake control module (EBCM) monitors the ignition voltage level available on the ignition 1 circuit. A low voltage condition prevents the system from operating properly. If the EBCM detects low voltage on the ignition 1 circuit, DTC C0901 will set.

Conditions for Running the DTC

    • The ignition is ON.
    • The vehicle speed is greater than 3 km/h (1.8 mph)

Conditions for Setting the DTC

The EBCM detects that the ignition voltage is less than 6.5 volts for 7 seconds.

Action Taken When the DTC Sets

The BRAKE indicator turns ON.

Conditions for Clearing the DTC

    • The DTC will pass when the ignition voltage is greater than 6.5 volts for 1 second.
    • The EBCM automatically clears a history DTC when a current DTC is not detected in 100 consecutive ignition cycles.

Diagnostic Aids

A low voltage DTC in multiple modules indicates a concern in the charging system.

Reference Information

Schematic Reference

Antilock Brake System Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

    •  ABS Description and Operation
    •  Charging System 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 Testing

  1. Ignition OFF, disconnect the harness connectors at the EBCM.
  2. Ignition OFF and scan tool disconnected, open and close the driver door, and wait 1 minute. Test for less than 5 ohms between the ground circuit terminals listed below and ground.
  3. • Terminal C X1
    • Terminal 1 X2
    • Terminal 32 X2
    If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Verify that a test lamp illuminates between the B+ circuit terminals listed below and ground.
  5. • Terminal A X1
    • Terminal 16 X2
    • Terminal 47 X2
    If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  6. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal B X1 and ground.
  7. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  8. If all circuits test normal, replace the EBCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for EBCM replacement, setup, and programming.