C1204

DTC C1204 Right Front Wheel Speed Excessive Variation






Circuit Description
As the wheel is rotated, the speed sensor produces an AC voltage that increases with wheel speed. The EBCM uses the frequency of the AC signal to calculate wheel speed. The speed sensor is connected to the EBCM by a twisted pair of wires. Twisting reduces noise susceptibility that may cause a DTC to set.

Conditions for Setting the DTC
All of the following must be true for C1204 to set.
^ C1200 or C1203 or C1206 or C1209 not current.
^ Brake switch off.
^ The right front wheel speed is accelerating or decelerating beyond reasonable limits.

Action Taken When the DTC Sets
^ The solenoid relay opens, removing power from the pump motor and solenoids.
^ DTC C1204 is stored.
^ ABS disabled, ABS Warning Lamp turns on.

Conditions for Clearing the DTC
^ If the conditions that set DTC C1204 are no longer present, the DTC may be cleared by using the proper scan tool.
^ The DTC that has not occurred in 100 drive cycles will be cleared from history data.

Diagnostic Aids
Thoroughly inspect the wiring and connectors when diagnosing intermittent DTC(s). This will include the following.
^ Removal of the protective conduit and inspection for wiring for damage, shorts and contamination.
^ Inspection for improperly formed and/or damaged terminals.
^ Checking terminal contact (retention force) by using a spare male/female terminal.
^ Removal of the terminals from the connectors to check for proper terminal to wire crimp.

If the drivers comments reflect that the ABS Warning Lamp is on only during moist environmental changes (rain, snow, vehicle wash), all wheel speed sensor circuitry should be thoroughly inspected for signs of water intrusion. If the DTC is not current, simulate the effects of water intrusion. Use the following procedure. Spray the suspected area with a 5% salt-water solution. Then test-drive the vehicle over various road surfaces such as (bumps, turns, etc.) above 24 kph (15 mph). If the DTC sets then replace the suspected harness and/or sensor.

A careful visual inspection of the wheel speed sensor for damaged such as cracks and damage should be performed. If the DTC sets at the same speed every drive cycle, the wheel speed sensor is most likely damaged. Failure to perform the previous steps carefully and fully can result in misdiagnosis, unnecessary component replacement and reoccurrence of DTC C1204.








DTC Troubleshooting