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 AN ACTIVE DTC
- With the scan tool, read Drivetrain Control Module (DTCM) DTCs and record on the repair order.
- Record the Environmental Data.
- With the scan tool, erase DTCs.
- Using the recorded Environmental Data, along with the When Monitored and Set Conditions above, operate the vehicle in the conditions that set the DTC.
- With the scan tool, read DTCM DTCs.
Did the DTC return?
Yes
- Go To 2
No
- Perform the TESTING FOR AN INTERMITTENT CONDITION diagnostic procedure. Refer to TESTING FOR AN INTERMITTENT CONDITION .
- CHECK THE (F946) FUSED IGNITION RUN/START CONTROL OUTPUT CIRCUIT FOR AN OPEN OR HIGH RESISTANCE
- Turn the ignition off.
- Disconnect the Front Axle Disconnect (FAD) Module harness connector.
- Disconnect the DTCM harness connector.
- Turn the ignition on.
- Using a 12-volt test light connected to ground, check the (F946) Fused Ignition Run/Start Control Output circuit at the DTCM C1 harness connector and the FAD Module 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 3
No
- Repair the (F946) Fused Ignition Run/Start Control Output circuit for an open or high resistance.
- Perform the DTCM VERIFICATION TEST. Refer to DTCM VERIFICATION TEST .
- CHECK THE (G304) FRONT AXLE LOCK CONTROL CIRCUIT FOR A SHORT TO GROUND
- Turn the ignition off.
- Check for continuity between ground and the (G304) Front Axle Lock Control circuit at the DTCM C1 harness connector.
Is there continuity between ground and the (G304) Front Axle Lock Control circuit?
Yes
- Repair the (G304) Front Axle Lock Control circuit for a short to ground.
- Perform the DTCM VERIFICATION TEST. Refer to DTCM VERIFICATION TEST .
No
- Go To 4
- CHECK THE (G304) FRONT AXLE LOCK CONTROL CIRCUIT FOR AN OPEN OR HIGH RESISTANCE
- Measure the resistance of the (G304) Front Axle Lock Control circuit between the DTCM C1 harness connector and the FAD Module harness connector.
Is the resistance below 3.0 Ohms?
Yes
- Go To 5
No
- Repair the (G304) Front Axle Lock Control circuit for an open or high resistance.
- Perform the DTCM VERIFICATION TEST. Refer to DTCM VERIFICATION TEST .
- Measure the resistance of the (G304) Front Axle Lock Control circuit between the DTCM C1 harness connector and the FAD Module harness connector.
- REPLACE THE FAD MODULE
- Replace the FAD Module in accordance with the Service Information.
- Turn the ignition on.
- With the scan tool, clear DTCs in the DTCM.
- Using the recorded Environmental Data, along with the When Monitored and Set Conditions above, operate the vehicle in the conditions that set the DTC.
- During the test drive, move the Transfer Case Selector Switch (if equipped) to each position several times in accordance with the Service Information.
- With the scan tool, read DTCM DTCs.
Did the DTC return?
Yes
- Go To 6
No
- The new FAD Module repaired the problem.
- Perform the DTCM VERIFICATION TEST. Refer to DTCM VERIFICATION TEST .
- CHECK RELATED HARNESS CONNECTIONS
- Disconnect all DTCM harness connectors.
- Disconnect all related in-line harness connections (if equipped).
- Disconnect the related component harness connectors.
- Inspect harness connectors, component connectors, and all male and female terminals for the following conditions:
- Proper connector installation.
- Damaged connector locks.
- Corrosion.
- Other signs of water intrusion.
- Weather seal damage (if equipped).
- Bent terminals.
- Overheating due to a poor connection (terminal may be discolored due to excessive current draw).
- Terminals that have been pushed back into the connector cavity.
- Perform a terminal drag test on each connector terminal to verify proper terminal tension.
Repair any conditions that are found.
- Reconnect all DTCM harness connectors. Be certain that all harness connectors are fully seated and the connector locks are fully engaged.
- Reconnect all in-line harness connectors (if equipped). Be certain that all connectors are fully seated and the connector locks are fully engaged.
- Reconnect all related component harness connectors. Be certain that all connectors are fully seated and the connector locks are fully engaged.
- With the scan tool, erase DTCs.
- Using the recorded Environmental Data, along with the When Monitored and Set Conditions above, operate the vehicle in the conditions that set the DTC.
- With the scan tool, read DTCM DTCs.
Did the DTC return?
Yes
- Replace the DTCM in accordance with the Service information. Refer to MODULE, DRIVETRAIN CONTROL (DTCM), REMOVAL and MODULE, DRIVETRAIN CONTROL (DTCM), INSTALLATION .
- Perform the DTCM VERIFICATION TEST. Refer to DTCM VERIFICATION TEST .
No
- The wiring or poor connection problem has been repaired.
- Perform the DTCM VERIFICATION TEST. Refer to DTCM VERIFICATION TEST .
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.