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
^ MB991958: Scan Tool (MUT-III Sub Assembly)
^ MB991824: Vehicle Communication Interface (V.C.I.)
^ MB991827: MUT-III USB Cable
^ MB991911: MUT-III Main Harness B (Vehicles without CAN communication system)
^ MB991529: Diagnostic Trouble Code Check Harness
STEP 1. Using scan tool MB991958, check data list.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958 to the data link connector.
2. Start the engine.
3. Set scan tool MB991958 to the data reading mode, and check the data list items by driving the vehicle.
^ Item 11 (DTC 11 is set): Front right ABS sensor
^ Item 12 (DTC 12 is set): Front left ABS sensor
^ Item 13 (DTC 13 is set): Rear right ABS sensor
^ Item 14 (DTC 14 is set): Rear left ABS sensor
4. Turn the ignition switch to the "LOCK" (OFF) position.
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 then go to Step 11
STEP 3. Inspect the wheel speed sensor or ABS rotor.
Refer to Hydraulic Control Assembly; Service and Repair; Procedures.
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 wheel speed sensor circuit at the ABS-ECU connector B-118.
1. Disconnect the 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, 27 and 28, or 11 and 17.
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 terminal 16 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 terminal 16 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 terminal 10 and wheel speed sensor
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 terminal 10 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 terminal 28 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 terminal 28 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 terminal 11 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 terminal 11 and wheel speed sensor
YES: Repair it and then go to Step 11.
NO: Go to Step 11.
STEP 9. Measure 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. Recheck for diagnostic trouble code.
Q: Do the diagnostic trouble codes 11, 12, 13, 14, 21, 22, 23 or 24 reset?
YES: Go to Step 1.
NO: The procedure is complete.