C1209

DTC C1209





GENERAL DESCRIPTION
The wheel speed sensor is the essential component the ABS ECU uses to calculate vehicle speed and to determine whether wheel lock occurs. For example, rear wheel speed signal is used as a reference value, for vehicle speed, in front wheel drive vehicles, and if a difference between front and rear wheel speed occurs, then ABS control is performed. Wheel speed sensor is active hall-sensor type and good at temperature and noise characteristic. A digital wave is produced as the tone wheel rotates according the hall sensor principle. Frequency of duty wave is changed in proportion to rotation of tone wheel and HECU calculates vehicle speed by this frequency.

DTC DESCRIPTION
The ABS ECU monitors the wheel speed sensor circuit continuously. A direct current is supplied in the wheel-speed sensor by a power source in the input amplifier of the control unit. If the WSS circuit is broken, in that case a fault is detected by detecting abnormal input current. HECU cuts off the voltage supply to wheel sensor channel which had a fault to prevent vehicle's damage due to super heated harness. If one or more defects has detected, DTC code of defected wheel will be stored. Mutual short between sensors is detected by executing self diagnosis successively at corresponding wheel when ignition ON. Warning lamp is turned OFF unless fault is detected any more when the IG KEY is turned ON again.

DTC DETECTING CONDITION:

MONITOR SCANTOOL DATA
1. Engine "ON".
2. Connect Scantool to Data Link Connector (DLC).
3. Start and drive vehicle in gear and maintain vehicle speed at approx. 10 km/h or more (6 mph or more)
4. Monitor the "Wheel speed sensor" parameter on the Scantool.
Specification: Approx. 10 km/h or more (6 mph or more)





5. Is parameter displayed within specifications?
YES
Fault is intermittent caused by poor connection in wheel speed sensor harness and/or HECU's connector or was repaired and HECU memory was not cleared. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.
NO
Go to "W/Harness Inspection" procedure.

TERMINAL & CONNECTOR INSPECTION
1. Many malfunctions in the electrical system are caused by poor harness(es) and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.
2. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.
3. Has a problem been found?
YES
Repair as necessary and then go to "Verification of Vehicle Repair" procedure.
NO
Go to "Power Circuit Inspection" procedure.

POWER SUPPLY CIRCUIT INSPECTION
1. Ignition "ON".
2. Measure voltage between terminal (front:"1", rear:"2") of the wheel speed sensor harness connector and chassis ground.
Specification: Approx. B+





3. Is the measured voltage within specifications?
YES
Go to "Signal Circuit Inspection" procedure.
NO
Check for open or short to GND in wheel speed sensor harness between terminal (front:"1", rear:"2") of the wheel speed sensor harness connector and terminal of the HECU harness connector. Repair as necessary and then go to "Verification of vehicle Repair" procedure. If OK, go to "Component inspection" procedure.





SIGNAL CIRCUIT INSPECTION
1. Lift the vehicle by lift.
2. Ignition "ON".
3. Turn the wheel with hand.
4. Measure wave between terminal of the HECU harness connector and chassis ground.
Specification: High: 1.4 V, Low: 0.7 V





5. Is the measured wave within specifications?
YES
Go to "Component Inspection" procedure.
NO
Check for open or short to GND in wheel speed sensor harness between terminal (front:"2", rear:"1") of the wheel speed sensor harness connector and terminal of the HECU harness connector. Repair as necessary and then go to "Verification of vehicle Repair" procedure. If OK, substitute with a known-good Wheel speed sensor and check for proper operation. If problem is corrected, replace Wheel speed sensor and then go to "Verification of Vehicle Repair" procedure.

COMPONENT INSPECTION
1. Ignition "OFF".
2. Engine "ON".
3. Does warning lamp remain On?
YES
Substitute with a known-good HECU and check for proper operation. If problem is corrected, replace HECU and then go to "Verification of Vehicle Repair" procedure.
NO
Fault is intermittent caused by open or short of wheel speed sensor harness, faulty wheel speed sensor. Go to the applicable troubleshooting procedure.

VERIFICATION OF VEHICLE REPAIR
After a repair, it is essential to verify that the fault has been corrected.

1. Connect Scantool and select "Diagnostic Trouble Codes (DTCs)" mode
2. Using a Scantool, clear DTC.
3. Operate the vehicle within DTC Detecting Condition in General Information. (Start and drive vehicle in gear and maintain vehicle speed is approx. 10 km/h or more (6 mph or more))
4. Are any DTCs present?
YES
Go to the applicable troubleshooting procedure.
NO
System performing to specification at this time.