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 C0286 : Brake Fluid Flow Switch Circuit High

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Power Brake Booster Fluid Flow Switch Signal

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C0286

C0286

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Circuit/System Description

The electronic brake control module (EBCM) monitors the function of the brake fluid flow switch to assure that the switch opens and closes properly.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

The EBCM detects a open brake fluid flow switch for greater than 4.4 seconds.

Action Taken When the DTC Sets

    • The brake warning indicator illuminates.
    • A fast rate audible chime turns ON.

Conditions for Clearing the DTC

The condition for setting the DTC are no longer present.

Diagnostic Aids

    •  This DTC may be caused by a fluid flow switch that sticks open intermittently.
    •  Thoroughly inspect connections or circuitry that may cause an intermittent malfunction.
    •  The ground circuit 151 of the Park Brake Booster Fluid Flow Switch should be checked for an intermittent or open.

Reference Information

Schematic Reference

Hydraulic Brake Schematics

Connector End View Reference

Component Connector End Views

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

Clear the DTCs, Engine ON, allow the engine to idle for 10 seconds. Engine OFF for 10 seconds, Ignition ON, the DTC should set.

Circuit/System Testing

  1. Ignition OFF, disconnect the power brake booster fluid flow switch harness connector of the EBCM.
  2. Ignition OFF, test for less than 1.0 ohm between the ground circuit terminal B of the park brake booster fluid flow switch and ground.
  3. If greater than the specified range, test the ground circuit for an open/high resistance.
  4. Engine ON at idle, verify that a test lamp blinks ON then OFF, connected between the power brake booster fluid flow switch signal terminal 28 of the EBCM and a good ground.
  5. If the test lamp does not illuminate, test between the park brake booster fluid flow switch signal circuit terminal A and splice 111 for an open/high resistance. If the circuit tests normal, replace the EBCM.
    If the test lamp illuminates in a blinking manner ON then OFF, test between the park brake booster fluid flow switch signal circuit terminal A and splice 111 for a short to voltage. If the circuit tests normal, replace the park brake booster fluid flow switch.
  6. If all circuits test normal, replace the park brake booster fluid flow switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Important:  After doing a EBCM replacement, use the scan tool to perform a Tire Size/Wheel Base Calibration procedure in EBCM special functions. Refer to Electronic Brake Control Module Replacement

    •  Control Module References for EBCM replacement, setup, and programming
    •  Fluid Flow Switch Replacement