DTC 24
CIRCUIT OPERATION
- A toothed ABS rotor generates a voltage pulse as it moves across the pickup field of each wheel speed sensor.
- The amount of voltage generated at each wheel is determined by the clearance between the ABS rotor teeth and the wheel speed sensor, and by the speed of rotation.
- The wheel speed sensors transmit the frequency of the voltage pulses and the amount of voltage generated by each pulse to the ABS Electronic Control Unit (ABS-ECU).
- The ABS hydraulic unit modulates the amount of braking force individually applied to each wheel cylinder.
ABS DTC SET CONDITIONS
DTCs 11, 12, 13, 14 are output when signal is not input due to breakage of the (+) or (-) wire of one or more of the four wheel-speed sensors. DTCs 21, 22, 23, 24 are output in the following cases:
- Open circuit is not found but no input is received by one or more of the four wheel-speed sensors at 10 km/in (6 mph) or more.
- Sensor output drops due to a malfunctioning sensor or warped ABS rotor.
TROUBLESHOOTING HINTS
The most likely causes for these DTCs to set are:
DTC 11, 12, 13, 14
- Malfunction of the wheel speed sensor
- Damaged wiring harness or connector
- Malfunction of the hydraulic unit (Integrated with ABS-ECU)
DTC 21, 22, 23, 24
- Malfunction of the wheel speed sensor
- Damaged wiring harness and connector
- Malfunction of the hydraulic unit (Integrated with ABS-ECU)
- Malfunction of the ABS rotor
- Malfunction of the wheel bearing
- Excessive clearance between the sensor and ABS rotor
DIAGNOSIS
Required special tool: MB991223: Harness Set
STEP 1. Check the wheel speed sensor installation.
If the wheel speed sensor is bolted securely in place at the front knuckle or the rear knuckle, go to Step 2.
If the wheel speed sensor is not bolted securely in place at the front knuckle or the rear knuckle, install it properly.
STEP 2. Check wheel speed sensor circuit at the ABS-ECU connector A-02.
1. Disconnect connector A-02 and measure at the harness side.
2. Measure the resistance between the ABS-ECU connector terminals 1 and 3, 4 and 5, 6 and 7, 8 and 9.
Standard Value: 1.28 - 1.92 k ohms
If the resistance between terminals 1 and 3 is not within the standard value, go to Step 3.
If the resistance between terminals 6 and 7 is not within the standard value, go to Step 4.
If the resistance between terminals 4 and 5 or 8 and 9 is not within the standard value, go to Step 5.
If the resistance between is within the standard value, go to Step 6.
STEP 3. Check the harness wires between ABS-ECU connector A-02 and wheel speed sensor
If any harness wires between ABS-ECU connector A-02 and wheel speed sensor
If the harness wires are not damaged, go to Step 7.
NOTE: After inspecting intermediate connector C-06, inspect the wire. If intermediate connector C-06 is damaged, repair or replace it. Refer to Harness Connector Inspection. Component Tests and General Diagnostics If the connector has been repaired or replaced, go to Step 9.
STEP 4. Check the harness wires between ABS-ECU connector A-02 and wheel speed sensor
If any harness wires between ABS-ECU connector A-02 and wheel speed sensor
If the harness wires are not damaged, go to Step 7.
STEP 5. Check the harness wires between ABS-ECU connector A-02 and wheel speed sensor connector D-09
If any harness wires between ABS-ECU connector A-02 and wheel speed sensor connector D-09
If the harness wires are not damaged, go to Step 7.
NOTE: After inspecting intermediate connector C-18 or D-16, inspect the wire. If intermediate connector C-18 or D-16 is damaged, repair or replace it. Refer to Harness Connector Inspection. Component Tests and General Diagnostics If the connector has been repaired or replaced, go to Step 9.
STEP 6. Check the wheel speed sensor output voltage.
Output Voltage:
When measured with a voltmeter: 42 mV or more
When measured with oscilloscope (maximum voltage): 200 mV or more
If the voltage is below the specification, go to Step 7.
If the voltage meets the specification, replace the hydraulic unit (integrated with ABS-ECU) Then go to Step 9.
STEP 7. Check the wheel speed sensor or ABS rotor.
If there is damage in any of the check items, replace the wheel speed sensor.
Check items:
- Wheel speed sensor internal resistance
Standard value: 1.28 - 1.92 k ohms
- Wheel speed sensor insulation resistance
Standard value: 100 k ohms
- Toothed ABS rotor check
If the wheel speed sensor or ABS rotor is damaged, replace it. Then go to Step 9.
If the wheel speed sensor and ABS rotor are not damaged, go to Step 8.
STEP 8. Check the wheel bearing.
If the wheel bearing is damaged, replace it. Then go to Step 9.
STEP 9. Check the diagnostic trouble codes.
Confirm that diagnostic trouble codes 11, 12, 13, 14, 21, 22, 23 and 24 do not reset.