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 IF DTC IS CURRENT
- CHECK FOR ENGINE CHARGING SYSTEM DTCS
- With the scan tool, read Engine DTCs.
Are any Engine Charging System DTCs present?
Yes
- Repair any Charging System DTCs before proceeding. Refer to the DTC INDEX . After repairing the Charging System, perform the Transmission Verification test to verify the transmission and or controller was not damaged. Refer to 6F24 TRANSMISSION VERIFICATION TEST .
No
- Go To 3
- With the scan tool, read Engine DTCs.
- CHECK SYSTEM VOLTAGE
- CHECK IF VOLTAGE IS GREATER THAN 16.9 VOLTS
- Start the engine and raise the engine speed to 2000 RPM.
- With the scan tool, monitor the Transmission system voltage for at least 60 seconds.
Does the Transmission system voltage read above 16.9 volts for any period of time?
Yes
- Repair the charging system for an over charging condition. and repair any Charging System symptoms before proceeding. Refer to the DTC INDEX . After repairing the Charging System, perform the Transmission Verification test to verify the transmission and or controller was not damaged.
- Perform the TRANSMISSION VERIFICATION TEST. Refer to 6F24 TRANSMISSION VERIFICATION TEST .
No
- Go To 5
- VERIFY IF VEHICLE WAS JUMP STARTED WITH 24-VOLT SYSTEM
- Verify if the vehicle was jump started by another vehicle using a 24-volt charging system.
Was the vehicle jump started by another vehicle using a 24-volt charging system?
Yes
- This is the cause of the DTC. Erase the DTC and return the vehicle to the customer.
- Perform the TRANSMISSION VERIFICATION TEST. Refer to 6F24 TRANSMISSION VERIFICATION TEST .
No
- Go To 8
- Verify if the vehicle was jump started by another vehicle using a 24-volt charging system.
- CHECK THE TCM POWER INPUT CIRCUITS
- Turn the ignition off to the lock position.
- Disconnect the TCM C1 harness connector.
- Ignition ON, Engine Not Running.
- Using a 12-volt test light connected to ground, check the TCM Power Input circuits at the Transmission Control Module (TCM) C1 harness connector.NOTE:
The test light must illuminate brightly. Compare the brightness to that of a direct connection to the battery.
Does the test light illuminate brightly?
Yes
- Go To 7
No
- Repair the TCM Power Input circuits for an open or high resistance.
- Perform the TRANSMISSION VERIFICATION TEST. Refer to 6F24 TRANSMISSION VERIFICATION TEST .
- CHECK THE TCM GROUND CIRCUITS
- Ignition ON, Engine Not Running.
- Using a 12-volt test light connected to B(+), check the ground circuits at the Transmission Control Module (TCM) C1 harness connector.NOTE:
The test light must illuminate brightly. Compare the brightness to that of a direct connection to the battery.
Does the test light illuminate brightly?
Yes
- Replace and program the TCM in accordance with the service information. Refer to REMOVAL .
- Perform the TRANSMISSION VERIFICATION TEST. Refer to 6F24 TRANSMISSION VERIFICATION TEST .
No
- Repair the TCM grounds circuits for an open or high resistance.
- Perform the TRANSMISSION VERIFICATION TEST. Refer to 6F24 TRANSMISSION VERIFICATION TEST .
- INTERMITTENT WIRING AND CONNECTORS
- The conditions necessary to set this DTC are not present at this time.
- Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
- Wiggle the wires while checking for shorted and open circuits.
Were there any problems found?
Yes
- Repair as necessary.
- Perform the TRANSMISSION VERIFICATION TEST. Refer to 6F24 TRANSMISSION VERIFICATION TEST .
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.