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 Descriptors

DTC C1101: Base Brake System Pressure Sensor Circuit Performance

DTC C1102: Base Brake System Pressure Sensor Circuit Low Voltage

DTC C1103: Base Brake System Pressure Sensor Circuit High Voltage

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

5-Volt Reference

C1102

C1102

C1103

C1101

Brake Fluid Pressure Sensor Signal

C1102

C1102

C1103

C1101

Low Reference

--

C1102

--

--

Circuit/System Description

The brake pressure sensor monitors the line pressure down stream from the master cylinder. The ECM receives inputs from the brake pressure sensor and communicates via serial data with the SGCM for the hill hold functions.

Conditions for Running the DTC

C1101

    •  Engine is running and vehicle speed is above 40 km/h (25 mph), or engine is running and vehicle is stopped after reaching a speed equal to or greater than 40 km/h (25 mph).
    • DTCs C1102, C1103 or vehicle speed DTCs have not set.
    • The transmission is in drive.

C1102 or C1103

Ignition ON.

Conditions for Setting the DTC

C1101

The EBCM detects that the brake pressure sensor indicates the brake is on

C1102

The ECM detects a short to ground or open with the sensor signal circuit or the brake pressure sensor.

C1103

The ECM detects an open with the sensor ground or a short to voltage in either the signal circuit or the brake pressure sensor.

Action Taken When the DTC Sets

DTCs C1101, C1102 or C1103 are Type B DTCs.

Conditions for Clearing the DTC

DTCs C1101, C1102 or C1103 are Type B DTCs.

Reference Information

Schematic Reference

Hydraulic Brake Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Hill Hold Control Description and Operation

Electrical Information Reference

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

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the brake fluid pressure sensor.
  2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal A and ground.
  3. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  4. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal B and ground.
  5. If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
    If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  6. Verify the scan tool ECM Brake Fluid Pressure Sensor parameter is less than 0.15 volt.
  7. If greater than the specified range, test the signal circuit terminal for a short to voltage. If the circuit tests normal, replace the ECM.
  8. Install a 3A fused jumper wire between the signal circuit terminal C and the 5-volt reference circuit terminal B. Verify the scan tool ECM Brake Fluid Pressure Sensor parameter is greater than 4.75 volts.
  9. If less than the specified range, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
  10. If all circuits test normal, test or replace the brake master cylinder pressure sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Brake Master Cylinder Pressure Sensor Replacement
    •  Control Module References for ECM replacement, setup, and programming