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
- TEST FOR INTERMITTENT CONDITION
- Turn the ignition on.
- Clear all FCM DTC's.
- Shift the transmission into reverse.
- With the scan tool, read DTC's.
Does the scan tool read: B1668-REVERSE LAMP CONTROL CIRCUIT HIGH?
Yes
- Go to step 2
No
- The conditions that caused this code to set are not present at this time. Using the SYSTEM WIRING DIAGRAMS as a guide, inspect the wiring and connectors.
- Perform the BODY VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure
- (L1) BACK-UP LAMP FEED CIRCUIT SHORT TO VOLTAGE
- Turn the ignition off.
- Disconnect the IPM C2 harness connector.
- Turn the ignition on.
- Measure the voltage on the (L1) Back-up Lamp Feed circuit.
Is the voltage greater than 10.0 volts?
Yes
- Repair the (L1) Back-up Lamp Feed circuit for a short to voltage.
- Perform the BODY VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure
No
- Replace the IPM in accordance with the Service Information.
- Perform the BODY VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Front Control (FCM) - Standard Procedure
Use the Manual With the Right Hardware
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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.
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