GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2001 🢒 Firebird 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC C0166 or C0171

Circuit Description

The Master Cylinder Isolation valve, or TCS Prime valve solenoid circuits are supplied with battery power when the ignition is in the RUN position. The EBCM controls the valve functions by grounding the circuit when necessary.

Conditions for Setting the DTC

The EBCM senses a discrepancy such as an open, short to ground, or short to voltage in the circuit.

Action Taken When the DTC Sets
    • A malfunction DTC is stored.
    • ABS/TCS disabled
    • ABS/TCS Indicators are turned on.
    • The Red BRAKE Warning Indicator turns on.

Conditions for Clearing the DTC
    • Condition for DTC is no longer present and scan tool clear DTC function is used.
    • 100 ignition cycles pass with no DTC detected.

Test Description

The numbers below refer to step numbers on the Diagnostic Table.

  1. This step determines if the DTC is current.

Step

Action

Yes

No

Schematic Reference: Antilock Brake System Schematics

1

Did you perform the ABS Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - ABS

2

  1. Using a scan tool clear the DTC.
  2. Remove the scan tool from the DLC.
  3. Carefully drive the vehicle above 12 Km/h (8 mph) for several minutes.
  4. Turn the ignition switch to the OFF position.
  5. Install a scan tool.
  6. Turn the ignition switch to the ON position, engine off.
  7. Using the scan tool in Diagnostic Trouble Codes, check for DTCs.

Did any on of the DTCs C0060-C0095 reset as a current DTC?

Go to Step 3

Go to Diagnostic System Check - ABS

3

Replace the EBCM. Refer to Electronic Brake Control Module Replacement

Is the repair complete?

Go to Step 4

--

4
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the conditions for Running the DTC as specified in the supporting text.

Dose the DTC reset?

Go to Step 2

System OK