DTC A091: Open Stoplamp Switch During Deceleration

OPEN STOPLAMP SWITCH DURING DECELERATION





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 deceleration rates 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 input is seen.

Diagnosis
This test monitors and calculates the deceleration for each wheel on a continuous basis. A fault is stored if a deceleration of 6.4 km/h/second (4 mph/second) is seen on 3 separate occasions while the stoplamp switch is off. The deceleration must begin above 24 km/h (15 mph) and end below 16 km/h (10 mph).

Cause(s)
- The stoplamp switch is malfunctioning (contacts open all the time).
- The stoplamp switch fuse is blown.
- The power feed circuit for the stoplamp switch is open.
- The EBCM is faulty.

Fail Action
The ABS is not available since the stoplamp switch is not available. The ABS is disabled and the ABS warning lamp is turned on. The system commands a rehome to ensure that all motors are in the home position.

Test Description
The number(s) below refer to step(s) on the diagnostic table.
2. This indicates if the EBCM has received the stoplamp switch signal.
3. This step indicates the existence of an open circuit in the stoplamp switch or the rear combination light circuitry.
4. This step traces the open circuit to either the stoplamp switch input circuitry or the EBCM.
11. This step verifies that voltage is available at the stoplamp switch.
15. This step verifies that the stoplamp switch is functioning properly.

Diagnostic Aids
An intermittent malfunction may be caused by a poor connection, wire insulation that has been rubbed through, or a wire that is broken inside the insulation.
Check the frequency of the malfunction by using the enhanced diagnostic feature of the scan tool as described in "Scan Tool Diagnostics." Scan Tool Diagnostics
Any circuitry that is suspected of causing the intermittent complaint should be thoroughly checked 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.








DTC A091 - Open Stoplamp Switch During Deceleration