C1235

CIRCUIT DESCRIPTION
As a toothed ring passes by the wheel speed sensor, changes in the electromagnetic field cause the wheel speed sensor to produce an AC voltage signal. The frequency of the AC voltage signal is proportional to the wheel speed. The amplitude of the AC voltage signal is directly related to wheel speed and the proximity of the wheel speed sensor to the toothed ring. The proximity of the wheel speed sensor to the toothed ring is also referred to as the air gap.

CONDITIONS FOR SETTING THE DTC
^ Diagnostic Trouble Code (DTC) C1235 can set anytime after initialization.
^ A malfunction exists if either of the right rear wheel speed sensor circuits are open or shorted to voltage or ground.

ACTION TAKEN WHEN THE DTC SETS
^ A malfunction Diagnostic Trouble Code (DTC) stores.
^ The ABS disables.
^ The ABS warning indicator turns ON.

CONDITIONS FOR CLEARING THE DTC
^ The condition responsible for setting the Diagnostic Trouble Code (DTC) no longer exists and the Scan Tool Clear DTCs function is used.
^ 100 drive cycles pass with no DTCs detected. A drive cycle consists of starting the vehicle, driving the vehicle over 16 km/h (10 mph), stopping and then turning the ignition OFF.

DIAGNOSTIC AIDS
The following conditions may cause a malfunction:
^ A poor connection
^ Rubbed-through wire insulation
^ A broken wire inside the insulation
^ Faulty electrical circuits (open/high resistance, short to voltage or ground) between the RR wheel speed sensor and the Electronic Brake Control Module (EBCM)
^ Malfunctioning wheel speed sensor (high resistance)

Use the enhanced diagnostic function of the Scan Tool in order to measure the frequency of the malfunction.
If the customer's comments reflect that the amber ABS warning indicator is ON only during moist environmental changes (rain, snow, vehicle wash), inspect all the wheel speed sensor circuitry for signs of water intrusion. If the DTC is not current, clear all DTCs and simulate the effects of water intrusion by using the following procedure:
1. Spray the suspected area with a five percent saltwater solution. Add two teaspoons of salt to twelve ounces of water to make a five percent saltwater solution.
2. Test drive the vehicle over various road surfaces (bumps, turns, etc.) above 24 km/h (15 mph) for at least 30 seconds.
3. If the DTC returns, replace the suspected harness.

Thoroughly inspect any circuitry that may be causing the intermittent complaint for the following conditions:
^ Backed out terminals
^ Improper mating
^ Broken locks
^ Improperly formed or damaged terminals
^ Poor terminal-to-wiring connections
^ Physical damage to the wiring harness
Resistance of the wheel speed sensor will increase with an increase in sensor temperature.

Use the following procedure when replacing a wheel speed sensor or harness:
1. Inspect the wheel speed sensor terminals and harness connector for corrosion and/or water intrusion.
2. Replace the wheel speed sensor and jumper harness if evidence of corrosion or water intrusion exists.

TEST DESCRIPTION
2. This test checks the wheel speed sensor circuitry for the proper resistance values at the Electronic Brake Control Module (EBCM).
3. This test checks for a short to ground in the wheel speed sensor circuit.
4. This test checks for a short to voltage in either the high or the low wheel speed sensor signal circuits.
5. This test checks the wheel speed sensor for the proper resistance value.
6. This test checks for an open or high resistance in the wheel speed sensor signal high circuit.
7. This test checks for an open or high resistance in the wheel speed sensor signal low circuit.
8. This test checks for a short to ground in the wheel speed sensor signal high circuit.
9. This test checks for a short to ground in the wheel speed sensor signal low circuit.
10. This test determines if the wheel speed sensor signal high circuit is shorted to voltage.
11. This test determines if the wheel speed sensor signal low circuit is shorted to voltage.
13. This test determines if the malfunction is caused by the EBCM.

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DTC C1235 RR WHEEL SPEED CIRCUIT OPEN OR SHORTED