Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Diagnostic Test
- CHECK FOR DTC C1020-LEFT REAR WHEEL SPEED SENSOR CIRCUIT NOTE:
This DTC must be active for the results of this test to be valid.
- Turn the ignition on.
- With the scan tool, record and erase DTCs.
- Cycle the ignition switch from off to on.
- With the scan tool, read DTCs.
Does the scan tool display: C1020-LEFT REAR WHEEL SPEED SENSOR CIRCUIT active?
Yes
- Go To 2
No
- The condition that caused the symptom is currently not present. Inspect the related wiring for a possible intermittent condition. Look for any chafed, pierced, pinched, or partially broken wires.
- Perform the ABS-INTERMITTENT CONDITION TEST. Refer to STANDARD PROCEDURE .
- CHECK CONNECTOR/TERMINAL FOR DAMAGE NOTE:
Check all terminals for broken, bent, pushed out, or corroded terminals.
- Turn the ignition off.
- Inspect the Anti-Lock Brake Module harness connector, Left Rear WSS, and Left Rear WSS harness connector.
Is the Left Rear WSS or any of the connectors/terminals damaged?
Yes
- Repair as necessary.
- Perform the ABS VERIFICATION TEST. Refer to STANDARD PROCEDURE .
No
- Go To 3
- CHECK (B4) LEFT REAR WSS 12 VOLT SUPPLY CIRCUIT VOLTAGE
- CHECK (B4) LEFT REAR WSS 12 VOLT SUPPLY CIRCUIT FOR A SHORT TO GROUND
- Turn the ignition off.
- Disconnect the Left Rear WSS harness connector.
- Disconnect the Anti-Lock Brake Module harness connector.
- Using a 12-volt test light connected to 12-volts, probe the (B4) Left Rear WSS Supply circuit.
Does the test light illuminate brightly?
Yes
- Repair the (B4) Left Rear WSS Supply circuit for a short to ground.
- Perform the ABS VERIFICATION TEST. Refer to STANDARD PROCEDURE .
No
- Go To 5
- CHECK (B4) LEFT REAR WSS 12 VOLT SUPPLY CIRCUIT FOR AN OPEN
- Connect a jumper wire between ground and the (B4) Left Rear WSS Supply circuit in the Anti-Lock Brakes Module harness connector.
- Using a 12-volt test light connected to 12-volts, probe the (B4) Left Rear WSS Supply circuit.
Does the test light illuminate brightly?
Yes
- Replace the Anti-Lock Brakes Module in accordance with the Service Information.
- Perform the ABS VERIFICATION TEST. Refer to STANDARD PROCEDURE .
No
- Repair the (B4) Left Rear WSS Supply circuit for an open.
- Perform the ABS VERIFICATION TEST. Refer to STANDARD PROCEDURE .
- CHECK (B3) LEFT REAR WSS SIGNAL CIRCUIT FOR A SHORT TO GROUND
- Turn the ignition off.
- If not done previously, disconnect the Anti-Lock Brake Module harness connector.
- Turn the ignition on.
- Using a 12-volt test light connected to 12-volts, probe the (B3) Left Rear WSS Signal circuit.
Does the test light illuminate brightly?
Yes
- Repair the (B3) Left Rear WSS Signal circuit for a short to ground.
- Perform the ABS VERIFICATION TEST. Refer to STANDARD PROCEDURE .
No
- Go To 7
- CHECK (B3) LEFT REAR WSS SIGNAL CIRCUIT FOR AN OPEN
- Connect a jumper wire between ground and the (B3) Left Rear WSS Signal circuit in the Anti-Lock Brakes Module harness connector.
- Using a 12-volt test light connected to 12-volts, probe the (B3) Left Rear WSS Signal circuit.
Does the test light illuminate brightly?
Yes
- Go To 8
No
- Repair the (B3) Left Rear WSS Signal circuit for an open.
- Perform the ABS VERIFICATION TEST. Refer to STANDARD PROCEDURE .
- CHECK (B3) LEFT REAR WSS SIGNAL CIRCUIT SHORT TO VOLTAGE
Courtesy of CHRYSLER GROUP, LLC
- Turn the ignition on.
- Remove all jumper wires.
- Measure the voltage between the (B3) Left Rear WSS Signal circuit and ground.
Is the voltage above one volt?
Yes
- Repair the (B3) Left Rear WSS Signal circuit for a short to voltage.
- Perform the ABS VERIFICATION TEST. Refer to STANDARD PROCEDURE .
No
- Go To 9
- CHECK (B3) LEFT REAR WSS SIGNAL CIRCUIT AND (B4) LEFT REAR WSS 12 VOLT SUPPLY CIRCUIT SHORTED TOGETHER
Courtesy of CHRYSLER GROUP, LLC
- Turn the ignition off.
- Measure the resistance between the (B3) Left Rear WSS Signal circuit and the (B4) Left Rear WSS Supply circuit.
Is the resistance above 5.0 Ohms?
Yes
Go To 10
No
- Repair the (B3) Left Rear WSS Signal circuit and the (B4) Left Rear WSS Supply circuit for a short together.
- Perform the ABS VERIFICATION TEST. Refer to STANDARD PROCEDURE .
- LEFT REAR WHEEL SPEED SENSOR
- Replace the Left Rear Wheel Speed Sensor in accordance with the Service Information.
- Perform the ABS VERIFICATION TEST. Refer to STANDARD PROCEDURE .WARNING:
To avoid possible serious or fatal injury, check brake capability is available before road testing.
- Road test the vehicle over 40 km/h (25 mph.).NOTE:
Vehicle must be driven above 40 km/h (25 mph) for set conditions to be met.
- With the scan tool, read ABS DTCs.
Did DTC C1020-LEFT REAR WHEEL SPEED SENSOR CIRCUIT reset?
Yes
- Replace the Anti-Lock Brakes Module in accordance with the Service Information.
- Perform the ABS VERIFICATION TEST. Refer to STANDARD PROCEDURE .
No
- Test Complete.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.