C1206

DTC C1206





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 tolerance. Digital wave is produced as tone wheel rotate according as hall sensor principle. Frequency of duty wave is changed in proportion to rotation of tone wheel and HECU calculate vehicle speed by this frequency.

DTC DESCRIPTION
The ABS ECU monitors the wheel speed sensor circuit continuously. If the sensor signal current is continuously out of the specified range for 140 msec, then the HECU determines that the circuit is open/short, and sets this code. Warning lamp is turned OFF if the detected fault is not more than when the IG KEY is turned to ON again, and wheel speeds are more than 6.21 mph.

DTC DETECTING CONDITION (part 1):

DTC DETECTING CONDITION (part 2):

DTC DETECTING CONDITION (part 3):

DTC DETECTING CONDITION (part 4):

TERMINAL AND CONNECTOR INSPECTION
1. Many malfunctions in the electrical system are caused by poor harness 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 CIRCUIT INSPECTION
1. Ignition "ON" & Engine "OFF".
2. Measure voltage between terminal "1" of the wheel speed sensor harness connector and chassis ground.
Specification: Approximately B+





3. Is the measured voltage within specifications?
YES
^ Go to "Signal Circuit Inspection" procedure.
NO
^ Check for short to GND in wheel speed sensor harness between terminal 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, go to "Component Inspection" procedure.





SIGNAL CIRCUIT INSPECTION
1. Ignition "ON" & Engine "OFF".
2. Turn the wheel slowly with hand.
3. Measure voltage between terminal "2, 20, 6, 22" of the HECU harness connector and chassis ground.
Specification: Approximately High: 1.18 - 1.68 V, Low: 0.59 - 0.84 V








4. Is the measured voltage within specifications?
YES
^ Go to "Component Inspection" procedure.
NO
^ Check for short to GND in wheel speed sensor harness between terminal "2" of the wheel speed sensor harness connector and terminal "2, 20, 6, 22" 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. Start and drive vehicle in gear and maintain vehicle speed is approximately 6.21 mph or more
4. 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 short of wheel speed sensor harness, faulty wheel speed sensor and/or faulty HECU or was repaired and HECU memory was not cleared. 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 approximately 6.21 mph or more)
4. Are any DTCs present?
YES
^Go to the applicable troubleshooting procedure.
NO
^ System performing to specification at this time.