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.
- With the scan tool, clear all DTCs.
- Turn the Left Turn Signal on.
- With the scan tool, read DTCs.
Does the scan tool display active: B1644-REAR LEFT TURN LAMP CONTROL CIRCUIT HIGH?
Yes
- Go to step 2
No
- The condition that caused this symptom is currently not present. Check for an intermittent condition by inspecting the related wiring harness for chafed, pierced, pinched, and partially broken wires. Also, inspect the related connectors for broken, bent, pushed out, spread, corroded, or contaminated terminals. Repair as necessary.
- Perform the BODY VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Totally Integrated Power (TIPM) - Standard Procedure .
- CHECK (Z910) GROUND CIRCUITS
- (Z910) GROUND CIRCUIT OPEN
- Measure the resistance of the appropriate (Z910) Ground circuit(s) at the Left Rear Turn Signal Lamp assembly harness connector.
Is the resistance below 10.0 Ohms?
Yes
- Replace the Inoperative bulb in accordance with the Service Information.
- Perform the BODY VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Totally Integrated Power (TIPM) - Standard Procedure .
No
- Repair the appropriate (Z910) Ground circuit(s) for an open.
- Perform the BODY VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Totally Integrated Power (TIPM) - Standard Procedure .
- Measure the resistance of the appropriate (Z910) Ground circuit(s) at the Left Rear Turn Signal Lamp assembly harness connector.
- CHECK (L63) LEFT REAR TURN SIGNAL CONTROL CIRCUIT
- Turn the ignition on.
- With the Left Turn Signal still on and a 12-volt test light connected to ground, check the (L63) Left Rear Turn Signal Control circuit.
Does the test light blink brightly from on to off with the turn signal indicator?
Yes
- Replace the Inoperative bulb in accordance with the Service Information.
- Perform the BODY VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Totally Integrated Power (TIPM) - Standard Procedure .
No
- Go to step 5
- (L63) LEFT TURN SIGNAL CONTROL CIRCUIT OPEN
- Turn the ignition off.
- Disconnect the TIPM C7 harness connector.
- Measure the resistance of the (L63) Left Rear Turn Signal Control circuit between the Left Rear Tail Lamp assembly harness connector and the TIPM C7 harness connector.
Is the resistance below 10.0 Ohms?
Yes
- Go to step 6
No
- Repair the (L63) Left Rear Turn Signal Control circuit for an open.
- Perform the BODY VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Totally Integrated Power (TIPM) - Standard Procedure .
- (L63) LEFT REAR TURN SIGNAL CONTROL CIRCUIT SHORTED TO VOLTAGE
- Turn the ignition on.
- Measure for voltage on the (L63) Left Rear Turn Signal Control circuit.
Is there any voltage present?
Yes
- Repair short to voltage on the (L63) Left Rear Turn Signal Control circuit.
- Perform the BODY VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Totally Integrated Power (TIPM) - Standard Procedure .
No
- Replace the Totally Integrated Power Module (TIPM) in accordance with the Service Information.
- Perform the BODY VERIFICATION TEST. See DTC-Based Diagnostics/MODULE, Totally Integrated Power (TIPM) - Standard Procedure .
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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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