C1027

C1027 - LEFT REAR WHEEL SPEED SENSOR INPUT SIGNAL ERRATIC PERFORMANCE






For a complete wiring diagram, refer to the Wiring Information.

- When Monitored:
With the ignition on.

- Set Condition:
When the Left Rear WSS Signal is intermittently missing at a vehicle speed above at 40 kph (25 mph) or erratic wheel speed signal during acceleration or sensed wheel speed is different from other wheels.







DIAGNOSTIC TEST

1. CHECK FOR DTC C1027 - LEFT REAR WHEEL SPEED SENSOR INPUT SIGNAL ERRATIC PERFORMANCE






Note: The Anti-Lock Brake Module must sense ALL 4 wheels at 12 km/h (7.5 mph) before it will extinguish the ABS indicators.

1. Turn the ignition on.
2. With the scan tool, record and erase DTC's.
3. Cycle the ignition switch from off to on.
4. With the scan tool, read DTC's.

Does the scan tool display: C1027 - LEFT REAR WHEEL SPEED SENSOR INPUT SIGNAL ERRATIC PERFORMANCE and C1020 - LEFT REAR WHEEL SPEED SENSOR CIRCUIT?

Yes
- Refer to C1020-Left Rear Wheel Speed Sensor Circuit for the related symptom(s). Refer to C1020
- Perform ABS Verification Test-VER 1. Refer to ABS Verification Test


No
- Go To 2.

2. CHECK WHEEL SPEED SENSOR SIGNALS






1. Turn the ignition off.
2. With the scan tool, monitor ALL the WSS speeds while an assistant drives the vehicle.
3. Slowly accelerate as straight as possible from a stop to 40 km/h (25 mph).

Is the Left Rear WSS Speed showing 0 km/h (0 mph) or not matching other wheel speeds?

Yes
- Go To 3.

No
- Refer to the Intermittent Condition Diagnostic Procedure.
- Perform ABS Verification Test-VER 1. Refer to ABS Verification Test



3. CHECK LEFT REAR WSS LOOSENESS, INSPECT B3, B4 CIRCUITS/CONNECTORS/TERMINALS FOR DAMAGE






Note: Check all terminals for broken, bent, pushed out, or corroded terminals.

1. Turn the ignition off.
2. Inspect the Anti-Lock Brake Module harness connector, Left Rear WSS, and Left Rear WSS harness connector.
3. Inspect the Left Rear WSS for looseness and not properly fastened.
4. Inspect the (B3) Left Rear WSS Signal and (B4) Left Rear WSS Supply circuits between the Left Rear WSS and Anti-Lock Brake Module for damage.

Is the Left Rear WSS loose or any of the wiring/connectors/terminals damaged?

Yes
- Repair as necessary.
- Perform ABS Verification Test-VER 1. Refer to ABS Verification Test

No
- Go To 4.

4. CHECK LEFT REAR TONE WHEEL FOR DAMAGE

1. Turn the ignition off.
2. Inspect the Left Rear Tone Wheel for damage, missing teeth, cracks, or looseness.

Note: The Tone Wheel teeth should be perfectly square, not bent, or nicked.

Is the Left Rear Tone Wheel damaged?

Yes
- Repair as necessary.
- Perform ABS Verification Test-VER 1. Refer to ABS Verification Test

No
- Go To 5.


5. CHECK LEFT REAR WSS AIR GAP

1. Turn the ignition off.
2. Using a feeler gauge, measure the Left Rear WSS air gap.

Note: Refer to the appropriate service information, if necessary, for procedures or specifications.

Is the Left Rear WSS air gap within specifications?

Yes
- Go to 6.

No
- Repair as necessary.
- Perform ABS Verification Test-VER 1. Refer to ABS Verification Test


6. CHECK LEFT REAR WHEEL BEARING DAMAGE

1. Turn the ignition off.
2. Inspect the Left Rear wheel bearing for excessive runout or clearance.

Note: Refer to the appropriate service information, if necessary, for procedures or specifications.

Is the Left Rear Wheel Bearing damaged?

Yes
- Repair as necessary.
- Perform ABS Verification Test-VER 1. Refer to ABS Verification Test

No
- Go To 7.

7. CHECK LEFT REAR BRAKE HARDWARE DAMAGE

1. Turn the ignition off.
2. Visually inspect the Left Rear brake linings for contamination or overheating. Check for dragging, bent, or seized components/hardware.

Is any brake lining, component, or hardware damaged?

Yes
- Repair as necessary.
- Perform ABS Verification Test-VER 1. Refer to ABS Verification Test

No
- Go To 8.

8. ANTI-LOCK BRAKE MODULE - INTERNAL FAULT






1. Turn the ignition off.
2. Replace the Left Rear WSS.
3. With the scan tool, erase DTC's.
4. Road test the vehicle over 40 km/h (25 mph).
5. Turn the ignition on.
6. With the scan tool, read DTC's.

Did the DTC C1027 - LEFT REAR WHEEL SPEED SENSOR INPUT SIGNAL ERRATIC PERFORMANCE reset?

Yes
- Replace the Anti-Lock Brake Module.
- Perform ABS Verification Test-VER 1. Refer to ABS Verification Test

No
- Test Complete.