Jeep Tech Tip: 4WD Light On, DTC C140F Set – UnderhoodService
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Jeep Tech Tip: 4WD Light On, DTC C140F Set

Customers may indicate that the “Service 4WD” indicator in the instrument cluster is illuminated. They may also indicate that the transfer case will not shift from 4WD High, 4WD Low, and/or Neutral once the lamp is illuminated. Further investigation identifies that a Diagnostic Trouble Code C140F is stored or active in the Final Drive Control Modules (FDCM) memory.

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MODELS:
2005-2010 Grand Cherokee
2006-2010 Commander

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SYMPTOM/CONDITION:
Customers may indicate that the “Service 4WD” indicator in the instrument cluster is illuminated. They may also indicate that the transfer case will not shift from 4WD High, 4WD Low, and/or Neutral once the lamp is illuminated.

Further investigation identifies that a Diagnostic Trouble Code C140F is stored or active in the Final Drive Control Modules (FDCM) memory.

REPAIR PROCEDURE:
1. Using the scan tool, record the FDCM software number.

2. Was the FDCM software number 56044129AP, 56044199AP or 68235713AB?
a. YES – The FDCM software is at the latest level.
b. NO – Proceed to the next step.

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NOTE: Install a battery charger to ensure battery voltage does not drop below 13.2 volts. Do not allow the charging voltage to climb above 13.5 volts during the flash process.

NOTE: If this flash process is interrupted/aborted, the flash should be restarted.

3. Reprogram the FDCM with the latest software. Help using the scan tool diagnostic application for flashing an ECU is available by selecting “help” then “help contents” at the top of the scan tool diagnostic application window.

4. Clear any DTC’s that may have been set in other modules due to reprogramming. The scan tool application will automatically present all DTCs after the flash and allow the tech to clear them.

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5. **Disconnect the diagnostic scan tool.

NOTE: It may be possible for the FDCM to not power down if the scan tool is connected during the next step. Failure to disconnect the diagnostic scan tool may result in the inability to properly move DTC C140F from an Active Code to a Stored Code.**

6. Turn the ignition key OFF, making sure that the key remains OFF for at least 5 seconds. Then cycle the ignition key ON making sure that the key remains ON for at least 5 seconds. Perform a total of three ignition key OFF to ON cycles making sure that there is at least a 5-second pause between each key cycle.

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7. Using the scan tool, verify that DTC C140F is not active in the FDCM’s memory.

8. Is DTC C140F active in the FDCM’s memory?
a. YES: Please refer to the standard diagnostic information for C140F.
b. NO: Repair is complete.

NOTE: If C140F is still active, please ensure that all harness and connections into the FDCM and Transfer Case Actuator are free from any bent, loose or corroded terminals, and repair as necessary.

Courtesy of ALLDATA.

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