A091

Fig. 513 Code 91: Open Brake Switch During Deceleration:

DTC A091 Open Brake Switch During Deceleration:

Circuit Description:
This DTC is used to detect an open stoplamp switch in the non-ABS mode. The 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.

Failure Condition:
DTC AO91 can be set if three deceleration cycles occur without a stoplamp switch input to the EBCM.

Action Taken:
A DTC AO91 is stored ABS is disabled and the "ABS" indicator is turned on.

Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This step indicates if the stoplamp switch signal is being received by the EBCM.
2. This step indicates if an open circuit exists in the stoplamp switch or the rear combination lamp circuitry.
3. This step isolates the open circuit to either the stoplamp switch input circuitry or the EBCM.
4. This step verifies that voltage is available at the stoplamp switch.
5. This step verifies that the stoplamp switch is functioning properly.

Diagnostic Aids:
An "intermittent" malfunction may be 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 1.

Any circuitry that is suspected as 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.