C1494 on 2014-2018 Ram 2500: Service 4WD Light Causes and Fixes

What's Unique About the 2014-2018 Ram 2500

What's unique to this Ram platform is a known condition documented in a Technical Service Bulletin (TSB #68090604A). The manufacturer found that the C1494-92 code could be triggered intermittently during heavy acceleration, even when the Power Transfer Unit (PTU) was not faulty. The bulletin explicitly warns technicians *not* to replace the PTU if this specific symptom occurs, but to instead consult with FCA (now Stellantis) engineering. This strongly suggests a software calibration sensitivity rather than a guaranteed mechanical failure, making it crucial to avoid a common and expensive misdiagnosis of replacing the entire transfer case.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Illuminated 'Service 4WD' warning light on the dashboard
• Four-wheel drive system is inoperative
• Warning light may appear intermittently, especially during heavy acceleration.
• A grinding noise may be heard if the transfer case attempts to shift but fails.

Most Likely Causes

1. Drivetrain Control Module (DTCM) Software/Calibration Issue 🔴 High Probability A specific TSB (#68090604A) was issued for this exact problem, indicating it's a known issue where the system is too sensitive and flags a fault during normal events like heavy throttle.
   How to confirm: A Ram dealer must check the vehicle's VIN against their service database for any open TSBs or available software updates for the DTCM.
   Typical fix: Reprogramming (flashing) the Drivetrain Control Module with the latest software version. This is a dealer-only procedure.
   Est. part cost: $0
2. Wiring Harness or Connector Fault 🟡 Medium Probability The wiring harness for the transfer case is routed in a way that can lead to chafing. A common failure point is where the harness passes over the transfer case; a plastic retainer clip can break, allowing the harness to rub through. Additionally, the connectors for the Front Axle Disconnect (FAD) and transfer case motor are exposed and prone to water intrusion, leading to corroded pins.
   How to confirm: Visually inspect the wiring harness where it routes over the transfer case for smooth, worn areas or exposed wires. Unplug the connectors at the transfer case motor and FAD actuator and check for green or white corrosion on the pins. A multimeter can be used to check for continuity and shorts.
   Typical fix: Repairing the damaged section of the wiring harness by splicing in new wire with sealing 🎬 See how to repair a damaged 4WD wiring harness. heat-shrink connectors. If a connector is corroded, it may need to be replaced with a new pigtail. Re-securing the harness away from moving parts is critical.
   Est. part cost: $10-$50
3. Faulty Transfer Case Shift Motor (Actuator) ⚪ Low Probability → Shop Transfer Case Motor The electric motor that shifts the transfer case can fail internally, causing it to become slow, unresponsive, or blocked. This is a common failure item on many modern 4WD trucks.
   How to confirm: A bi-directional scan tool can be used to command the motor to shift while monitoring its response. If the motor fails to move or makes grinding noises, it is likely faulty. The motor can also be tested with a multimeter; a normal resistance reading is between 2.0 and 3.0 ohms.
   Typical fix: Replace the transfer case shift motor. This is often a bolt-on part attached to the transfer case. 🎬 Watch: Step-by-step transfer case shift motor replacement guide.
   Est. part cost: $150-$300

Rare But Worth Checking

• Internal Power Transfer Unit (PTU) Failure: → Shop Transfer Case Assembly While this is the component the code points to, it's often not the actual cause. The manufacturer TSB specifically warns against assuming the PTU has failed. This should only be considered after all software and electrical causes have been ruled out. A fluid check showing significant metal debris would confirm internal failure.
• Faulty Totally Integrated Power Module (TIPM): In rare cases, corrosion on the pins of the TIPM or an internal fault can cause communication errors and false codes related to the 4WD system. One owner reported finding corroded pins on the TIPM after replacing other components without success.

Diagnosis Steps

1. Read the code with a scanner capable of reading manufacturer-specific 'C' codes. Note if the suffix '-92' is present.
2. Interview the driver: Does the 'Service 4WD' light appear during heavy acceleration? If so, TSB #68090604A is highly relevant.
3. Contact a Ram dealer to check for any available software updates for the Drivetrain Control Module (DTCM) based on your VIN. This is the most likely and least expensive first step.
4. Thoroughly inspect the wiring harness going to the transfer case shift motor, specifically where it routes over the top of the transfer case. Look for a broken plastic retainer and signs of the harness rubbing through.
5. Inspect the connectors at the transfer case motor and the front axle disconnect (FAD) actuator. Unplug them and look for any signs of water intrusion or pin corrosion.
6. If wiring is good and software is up to date, use a bi-directional scan tool to command the transfer case shift motor to operate. Listen for normal operation.
🎬 Watch: Real-world diagnosis of a Ram 2500 4WD failure.
7. Check the fluid level and condition in the transfer case. Dark, burnt fluid or fluid with excessive metal shavings indicates an internal mechanical problem.
8. Only after confirming software is updated, wiring is intact, and the shift motor is faulty should you replace the motor. Only if the PTU shows signs of internal mechanical failure should it be considered for replacement.

Parts You'll Likely Need

• Drivetrain Control Module (DTCM) Reprogramming — As per TSB #68090604A, a software calibration issue is a very common cause for this code being set erroneously under heavy throttle.
  Trusted brands: Mopar (Dealer Service)
  OEM price range: $275-$350
  Aftermarket price range: N/A
• Transfer Case Shift Motor (OEM #68089746AC) — If the electric motor fails to actuate the transfer case fork correctly, it will set this performance code. This is a less common but possible hardware failure. The OEM part number supersedes 68089746AA and 68089746AB.
  Trusted brands: Dorman, Cardone, Mopar
  OEM price range: $250-$400
  Aftermarket price range: $150-$250

Related Codes That Often Appear With This One

• C147B — This code relates to the front axle disconnect (FAD) sensor circuit. Since the FAD and PTU work together to engage 4WD, a wiring problem affecting one can often affect the other. A Stellantis document (S2303000004) advises checking the FAD harness and connector for issues before replacing parts. The wiring harness for the FAD is known to corrode and break right at the connector.
• U0102 — This indicates a loss of communication with the Transfer Case Control Module. It strongly points to an electrical issue, such as a bad wiring harness, a corroded connector at the module or TIPM, or a faulty module, rather than a mechanical PTU failure.

Technical Service Bulletins (TSBs) & Recalls

• 68090604A: Warns that C1494-92 can be set by heavy throttle and advises against replacing the PTU without consulting engineering, pointing to a calibration issue.

Platform-Specific Known Issues

• TSB #68090604A documents an issue where code C1494-92 may set intermittently under heavy throttle, and explicitly advises against replacing the PTU without first consulting FCA engineering.
• The wiring harness that controls the transfer case motor has a plastic retainer clip that is prone to breaking. When it fails, the harness can sag and chafe against the top of the transfer case, eventually wearing through the insulation and causing shorts.

Mechanic-Grade Diagnostic Values

• Transfer Case Shift Motor Resistance — expected: 2.0 - 3.0 Ohms. Failure: A reading significantly outside this range suggests a faulty motor.
• T-Case Position Sensor 5-Volt Supply — expected: 4.5 - 5.5 Volts. Failure: Voltage below 4.5V or above 5.5V points to a wiring issue (open, short to ground, or short to voltage) or a faulty DTCM.
• CAN C Bus Termination Resistance — expected: Approximately 60 Ohms. Failure: 120 Ohms indicates a missing terminating resistor; near 0 Ohms indicates a short between the bus lines.

Scan Tool Commands That Help

• wiTECH (Dealer Tool): DTCM/PTU/RDM Reprogramming — Used to apply software updates as specified in Technical Service Bulletins to correct calibration issues that can falsely trigger C1494.
• wiTECH (Dealer Tool): PCM Misc Functions > Clear Mis-fire TLC — While not directly for C1494, this shows an example of a module-specific reset routine that may be required after a flash or repair to restore full functionality.
• AlfaOBD (Advanced DIY): Restore Configuration from Backup File — If changes made with AlfaOBD cause issues, this function allows restoring the Body Control Module (BCM) to a previously saved state, which can resolve communication-related faults.
• AlfaOBD (Advanced DIY): ABS Initialization — Required on Ram 2500/3500 after changing tire sizes to recalibrate the ABS module, which communicates with the drivetrain controller. Incorrect calibration can sometimes lead to performance-related codes.

Wiring & Ground Locations

• Drivetrain Control Module (DTCM) — Located in the passenger footwell area, requiring removal of the carpet for access.. This is the module that sets code C1494. All power, ground, and sensor signal tests related to the transfer case originate or terminate here. A loss of power or ground to this module will cause a U0102 code and disable the 4WD system.
• TIPM C4 Harness Connector — One of the large multi-pin connectors on the Totally Integrated Power Module (TIPM), which is the main fuse box under the hood.. Diagnostic procedures for related transfer case motor codes involve checking resistance between shift motor control circuits at this specific connector to isolate faults between the TIPM and the motor.
• Fuse F21 — In the underhood fuse box (TIPM).. This fuse provides battery power to the Drivetrain Control Module (DTCM). A real-world repair case showed that a corroded F21 fuse caused a 'No Communication' fault with the DTCM, leading to a 'Service 4WD' light.

Real Owner Repair Stories

• Pine Hollow Auto Diagnostics (YouTube) (2019 Ram 2500) — 'SERVICE 4WD' light on the dash, multiple 'lost communication with transfer case control module' codes (U0102).
  ❌ Tried (didn't work) Scanning for codes showed no communication with the Drivetrain Control Module (DTCM).
  ✅ What actually fixed it The power feed to the DTCM was dead. The technician traced it to fuse F21 (a 30A fuse, though a 20A was incorrectly installed) in the underhood fuse box. The fuse itself was corroded, causing an open circuit. Replacing the fuse restored power and communication to the module, clearing the fault.

OEM Part Supersession History

• 68089746AA → 68089746AB, then 68089746AC — Standard part revision and improvement by the manufacturer.
  Heads up: The latest part number, 68089746AC, is the correct service replacement for all previous versions on the 2014-2018 Ram 2500.

Model Year Variations Within This Range

• 2014-2018: The primary transfer cases used in the Ram 2500/3500 during this period were the BorgWarner BW 44-46 (electronic shift) and BW 44-47 (manual shift). Code C1494 applies specifically to the electronically shifted BW 44-46 model. The BW 44-44, which has clutches and requires a special fluid, is typically found in Ram 1500 models and is not the subject of this code on the HD trucks.