C1291

DTC C1291: Open Brake Lamp Switch Circuit During Deceleration (Part 1 Of 2):

DTC C1291: Open Brake Lamp Switch Circuit During Deceleration (Part 2 Of 2):

DTC C1291 Schematic:

Circuit Description
This DTC is used to detect an open stoplamp switch in the non-ABS mode. The Electronic Brake Control Module (EBCM) looks for a deceleration rate that would indicate braking action and verifies this assumption by requiring several repeats of this detection method. In each case, ABS will not be available since no stoplamp switch is seen.

Conditions for Setting the DTC
DTC C1291 can be set if three deceleration cycles occur with the stoplamp switch OFF.

Action Taken When the DTC Sets
A malfunction DTC is stored, ABS is disabled, and the amber ABS indicator lamp is turned ON.

Conditions for Clearing the DTC
^ Conditions for the malfunction are no longer present and the Tech 2 scan tool Clear DTC Information function is used.
^ One hundred drive cycles have passed with no malfunctions detected.

Diagnostic Aids
Inspect for a faulty stoplamp switch (contacts open all the time).
An intermittent malfunction is most likely caused by a poor connection, rubbed through wire insulation, or a wire that is broken inside the insulation.The frequency of the malfunction can be checked by using the Enhanced Diagnostic function of the Tech 2 scan tool, as described in Enhanced Diagnostics found in this section. Inspect the following harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wiring connections or physical damage to the wiring harness before component replacement:
^ EBCM connector C1.
^ Stoplamp switch connector.



Test Description
Numbers below refer to numbers on the diagnostic table.
3. Checks the EBCM's stoplamp switch status with a scan tool.
5. Checks for an open in CKT 20A/B/C/D/G.
7. Checks for power to stoplamp switch.
8. Checks stoplamp switch contacts (close with brake pedal pressed)