ABS
C1210Component Location:
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.
DTC Description
The ABS ECU monitors the wheel speed sensor signal continuously.
The failure detection is started if the original wheel speed changes erratically with a signal step of [Vx (n) - Vx (n-1)] > 25 km/h (15.5 mph). An offset of about 5 km/h (3.1 mph) will be added to the threshold in case rough road is detected or the number of interrupts from the wheel speed sensor reach a value of 40 per loop. An extrapolated wheel speed signal will be calculated, the start value is set to the vehicle reference speed.
Further on, the extrapolated wheel speed signal follows the calculated speed signal with a limited gradient of max 0.57 kph (0.4 mph) per loop.
Warning lamp is turned OFF unless additional faults are detected when the IG KEY is turned ON again, and wheel speed is more than 10 km/h (6.2 mph).
DTC Detecting Condition:
Specification:
Schematic Diagram:
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 or above 20 km/h. (12.4 mph)
4. Monitor the "WHEEL SPD SNSOR-RR" parameter on the Scantool.
Specification : Compare with other parameters related to wheel speed sensor.
If it is the same as other parameters, it is in normal condition.
5. Is parameter displayed within specifications?
YES - Fault is intermittent caused by faulty HECU or external noise, was repaired and HECU memory was not cleared. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair as necessary and then go to "Verification of vehicle Repair" procedure.
NO - Go to "Component Inspection" procedure.
Component Inspection
1. Ignition "OFF".
2. Disconnect the wheel speed sensor harness connector.
3. Connect resistance (approx. 100 ohms) to the wheel speed sensor signal circuit.
4. Measure waveform of the wheel speed sensor signal harness while turning the wheel.
Specification : High : Approx. 1.4 V, Low : Approx. 0.7 V (In case that 100 ohms resistance is used)
NOTE: Voltage of the waveform can be calculated by using following expression.
Voltage = Resistance • Current (High : 1.4 mA, Low : 0.7 mA)
5. Is the measured waveform within specifications and no missing signal?
YES
- Fault is intermittent caused by faulty HECU, wheel speed sensor or external noise, an interference between harnesses, was repaired and HECU memory was not cleared. Go to "Verification of Vehicle Repair" procedure.
- If OK, 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
- Check for improper installation of wheel speed sensor. If NG, repair as necessary and then go to "Verification of vehicle Repair" procedure.
- Check for damage of rotor teeth or wheel bearing. If NG, repair as necessary and then go to "Verification of vehicle Repair" procedure.
- 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.
Verification of Vehicle Repair
After a repair, it is essential to verify that the fault has been corrected.
1. Connect scan tool 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 at or above 20 km/h. (12.4 mph))
4. Are any DTCs present?
YES - Go to the applicable troubleshooting procedure.
NO - System performing to specification at this time.