As the wheel is rotated, the speed sensor produces an AC voltage that increases with wheel speed. The electronic brake control module (EBCM) uses the frequency of the AC signal to calculate the 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.
This diagnostic procedure supports the following DTC:
DTC C1205 Right Front Wheel Speed Sensor Input Signal Equals Zero
Conditions for Running the DTC
Ignition is in the ON position.
Conditions for Setting the DTC
All of the following must be true for DTC C1205 to set:
DTC C1200, C1203, C1206, or C1209 not current
ABS not active
Brake switch OFF
The right front wheel speed equals 0, and all of the remaining wheel speed sensors are greater than 8 km/h (5 mph) for at least 2.5 seconds.
Action Taken When the DTC Sets
The solenoid relay opens, removing power from the pump motor and solenoids.
DTC C1205 is stored.
ABS disabled, ABS warning lamp turns ON.
Conditions for Clearing the DTC
If the conditions that set the DTC C1205 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.
Thoroughly inspect the wiring and connectors when diagnosing intermittent DTCs. This will include the following:
Removal of the protective conduit and inspection of 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 driver comments reflect that the ABS warning lamp is ON only during moist environmental changes, such as rain, snow, vehicle wash, the 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 percent salt-water solution. Then test drive the vehicle over various road surfaces such as, bumps, turns, etc, above 24 km/h (15 mph). If the DTC sets then replace the suspected harness and/or sensor.
When measuring wheel speed sensor resistance, ensure the vehicle is at room temperature, since resistance will increase with temperature.
Failure to perform the previous steps carefully and fully can result in misdiagnosis, unnecessary component replacement, and reoccurrence of DTC C1205.
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Tuesday, October 23rd, 2012 AT 9:11 PM