DTC 12
DTC 12: Wheel Speed Sensor (Open Circuit or Short Circuit)
Part 1 of 2
Part 2 of 2
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 wires 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/h (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 are 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 or 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 Tools:
- MB991223: Harness Set
- MB991502: Scan Tool (MUT-II)
- MB991529: Diagnostic Trouble Code Check Harness
STEP 1. Using scan tool MB991502, check data list item 11, 12, 13, 14: Wheel speed sensor.
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991602.
1) Connect scan tool M6991502 to the data link connector.
2) Start the engine.
3) Set scan tool MB991502 to data reading mode for item 11, 12, 13, 14, Wheel speed sensor.
- With the engine running, reading on the speedometer nearly matches the indication on scan tool MB991502.
Q: Is the wheel speed sensor input normal?
YES: This malfunction is intermittent.
NO: Go to Step 2.
STEP 2. Check the wheel speed sensor installation.
- Q: Is the wheel speed sensor bolted securely in place at the front knuckle or the rear knuckle?
YES: Go to Step 3.
NO: Install it properly and go to Step 11.
STEP 3. Inspect the wheel speed sensor or ABS rotor.
Check items:
- Wheel speed sensor internal resistance: 1.24 - 1.64 k Ohms
- Insulation between the wheel speed sensor body and the connector terminals
- Toothed ABS rotor check
Q: Is the wheel speed sensor or ABS rotor damaged?
YES: Replace it and then go to Step 11.
NO: Go to Step 4.
STEP 4. Check the wheel speed sensor circuit at ABS-ECU connector B-118.
1) Disconnect connector B-118 and measure at the harness side.
2) Measure the resistance between the ABS-ECU connector terminals 16 and 26, 9 and 10, 11 and 17, or 27 and 28.
Standard Value: 1.24 - 1.64 k Ohms
Q: Is the resistance between terminals 16 and 26, 9 and 10, 27 and 28, or 11 and 17 within the standard value?
When resistances between all terminals are within the standard value.: Go to Step 9.
When resistance between terminals 16 and 26 is not within the standard value.: Go to Step 5.
When resistance between terminals 9 and 10 is not within the standard value.: Go to Step 6.
When resistance between terminals 27 and 28 is not within the standard value.: Go to Step 7.
When resistance between terminals 11 and 17 is not within the standard value.: Go to Step 8.
STEP 5. Check the harness wires between ABS-ECU connector B-118 and wheel speed sensor
NOTE: After inspecting ABS-ECU connector B-118, intermediate connector A- 13 and wheel speed sensor
Q: Is the harness wire between ABS-ECU connector B-118 and wheel speed sensor
YES: Repair it and go to Step 11.
NO: Go to Step 11.
STEP 6. Check the harness wires between ABS-ECU connector B-118 and wheel speed sensor front: RH> connector A-27.
NOTE: After inspecting ABS-ECU connector B-118, intermediate connector C-111, C-122 and wheel speed sensor
Q: Is the harness wire between ABS-ECU connector B-118 and wheel speed sensor
YES: Repair it and go to Step 11.
NO: Go to Step 11.
STEP 7. Check the harness wires between ABS-ECU connector B-118 and wheel speed sensor
NOTE: After inspecting ABS-ECU connector B-118, intermediate connector C-122, C-128, D-14 and wheel speed sensor
Q: Is the harness wire between ABS-ECU connector B-118 and wheel speed sensor
YES: Repair it and then go to Step 11.
NO: Go to Step 11.
STEP 8. Check the harness wires between ABS-ECU connector B-118 and wheel speed sensor
NOTE: After inspecting ABS-ECU connector B-118, intermediate connector C-122, C-128, D-14 and wheel speed sensor
Q: Is the harness wire between ABS-ECU connector B-118 and wheel speed sensor
YES: Repair it and then go to Step 11.
NO: Go to Step 11.
STEP 9. Check the wheel speed sensor output voltage.
Output Voltage:
- When measured with a voltmeter: 42 mV or more
- When measured with an oscilloscope (maximum voltage): 200 mV or more
Q: Does the voltage meet the specification?
YES: Replace the hydraulic unit (integrated with ABS-ECU) and then go to Step 11.
NO: Go to Step 10.
STEP 10. Check the wheel bearing.
If play on the wheel bearing is not within the standard value, replace the wheel bearing.
Limit Value: 0.05 mm (0.002 inch)
Q: Is play on the wheel bearing within the standard value?
YES: Go to Step 11.
NO: Replace it and then go to Step 11.
STEP 11. Check the diagnostic trouble codes.
Q: Do the diagnostic trouble codes 11, 12, 13, 14, 21, 22, 23 or 24 reset?
YES: Go to Step 1.
NO: This diagnosis is complete.