DTC 91

Fig. 573 Code 91: Open Brake Switch Contacts During Deceleration:

DTC's 92, 93, 94, & 95 Brake Switch Wiring Schematic:

Circuit Description:
This DTC is used to detect an open brake switch in the non-ABS mode. The EBCM/EBTCM 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 brake switch is seen.

DTC Will Set When:
DTC 91 can be set if three deceleration cycles occur with the brake switch "OFF."

Action Taken:
A malfunction DTC is stored, ABS is disabled and the ABS indicator lamp is turned "ON."

DTC Chart Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Indicates if the brake switch signal is being received by the EBCM/EBTCM.
2. Indicates if an open circuit exists in the brake switch or brake lamp circuitry.
3. Checks for an open in the brake switch input circuit.
4. Ensures malfunction was not due to poor terminal contact.
5. Checks for voltage entering the brake switch.
6. Checks for voltage exiting the brake switch.

Diagnostic Aids:
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 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.