C1291

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Circuit Description
Diagnostic Trouble Code (DTC) C1291 detects an open brake switch. The Electronic Brake Control Module (EBCM) looks for deceleration rates that may indicate braking action. The EBCM verifies braking action by repeating the method for finding deceleration rates that indicate braking action several times. In each case, the Antilock Brake System (ABS) will not be available because the EBCM 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 disables.
- The ABS warning indicator turns ON.

Conditions for Clearing the DTC
- The condition responsible for setting the DTC no longer exists and the Scan Tool Clear DTCs function is used.
- 100 drive cycles pass with no DTCs detected. A drive cycle consists of starting the vehicle, driving the vehicle over 16 km/h (10 mph), stopping and then turning the ignition off.

Diagnostic Aids
The following conditions may cause an intermittent malfunction:
- A poor connection
- Rubbed-through wire insulation
- A broken wire inside the insulation
Use the enhanced diagnostic function of the Scan Tool in order to measure the frequency of the malt unction.
Thoroughly inspect any circuitry that may cause the intermittent complaint for the following conditions:
- Backed out terminals
- Improper mating
- Broken locks
- Improperly formed or damaged terminals
- Poor terminal-to-wiring connections
- Physical damage to the wiring harness
- Sticking or malfunctioning stoplamp switch

IMPORTANT: Zero the J 39200 test leads before making any resistance measurements. Refer to the J 39200 user's manual.