C1291

Part 1 Of 2:

Part 2 Of 2:

Circuit Description
DTC C1291 detects an open brake switch in the non-ABS mode. The EBCM/EBTCM looks for deceleration rates that may indicate braking action. The EBCM/EBTCM verifies braking action by repeating the method for finding deceleration rates that indicate braking action several times. In each case, the ABS will not be available because the EBCM/EBTCM does not see the brake switch input.

Conditions For Setting The DTC
DTC C1291 can set if three deceleration cycles within the specified rate occur during the current ignition cycle with the brake switch off.

Action Taken When The DTC Sets
^ A malfunction DTC stores.
^ The ABS/TCS disables.
^ The amber ABS/TCS warning indicators turns on.

Conditions for Clearing The DTC
^ The condition responsible for setting the DTC no longer exists and the Scan Tool Clear DTC function is used.
^ 100 drive cycles pass with no DTC detected.

Diagnostic Aids
Use the enhanced diagnostic function of the Scan Tool in order to measure the frequency of the malfunction. Refer to the Scan Tool manual for the procedure. Use the Data List of the Scan Tool verify proper brake switch operation. The Data List should display the brake switch as the brake is applied within 25 mm (1.0 inch) of brake pedal travel.
Thoroughly inspect any circuitry that may cause the intermittent complaint for the following conditions:
^ Rubbed-through wire insulation
^ A broken wire inside the insulation
^ Backed out terminals
^ Improper mating
^ Broken locks
^ Improperly formed or damaged terminals
^ Poor terminal-to-wiring connections
^ Physical damage to the wiring harness

Important: Zero the J39200 test leads before making any resistance measurements.