Antilock Braking System (ABS)

Code 18: ABS Relay Coil Circuit To Shorted To Battery Or Coil Shorted.:

DTC 18 ABS Relay Coil Circuit Shorted To Battery Or Coil Shorted:

Circuit Description:
Ignition voltage is supplied to terminal "86" of the ABS relay. The EBCM/EBTCM is then able to energize the pull-in coil by completing the ground circuit at terminal "2" of the EBCM/EBTCM. The magnetic field created closes the ABS relay contacts and allows battery voltage and current to be supplied to the EBCM/EBTCM, which supplies power to the motors and solenoids.

DTC Will Set When:
DTC 18 can be set after the EBCM/EBTCM commands the ABS relay "ON." This test monitors the availability of current/voltage to the motors and solenoids. A malfunction of this type will not allow voltage to be available to the motors and solenoids; therefore, ABS operation would not be allowed if required. DTC 86 is set with DTC 18 if the rear channel is not expected to be in the home position.

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 EBCM/EBTCM is capable of controlling the ABS relay as commanded.
2. With the ABS relay removed, voltage should not be available at terminal "85". Any voltage at this point would indicate that the ABS relay control circuit was shorted to a voltage source.
3. Checks for a short across the ABS relay coil.
4. Checks for an internal short in the ABS relay between the BATTERY feed terminal "30" and the relay pull-in coil.
5. Ensures short to BATTERY was not due to physical damage of the EBCM/EBTCM connector.

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.