01 B0042, B0043, and B0044: Left Front or Driver Frontal Deplo… • 02 Serpentine Belt Noise: Causes, Effects, and How to Keep You… • 03 From Lap Belts to Three-Point Safety Belts: A History of Ve… • 04 10 Engine-Killing Behaviors Every Car Owner Must Avoid • 05 How to Start a Rebuilt Engine for the First Time • 06 Sensing the Power: A Comprehensive Guide to Automatic Trans… • 07 This Is Why The Air Recirculation Button Is So Important • 08 Decoding Transmission Types: Manual, Automatic, CVT, and DCT • 09 Can a Bad Alternator Cause Power Steering Problems? • 10 10 Lathe Machine Processes That Every Manufacturer Should K… •

DTC codes / Chrysler codes / P1479

P1479 · ChryslerTransmission Fan Relay Circuit Open Or Shorted

P1479 on Chrysler vehicles indicates that the transmission control module (TCM) has detected an open or shorted circuit in the transmission fan relay control circuit. The TCM monitors the relay's control wire and expects a specific voltage when the relay is commanded on or off; a deviation outside the expected range sets this code.

SystemPowertrain
Code typeChrysler specific
SeverityMedium
Fix difficultyIntermediate
AreaAuxiliary emission controls

Symptoms you may notice

  • Illumination of the malfunction indicator lamp (MIL) on the instrument cluster
  • Transmission may enter limp mode or default to a fixed gear
  • Overheating of the transmission fluid, especially during heavy load or towing
  • Fan may run continuously or not at all, depending on the type of circuit fault
  • Often no symptoms besides the warning light, as the fan may only be needed under extreme conditions

Common causes, most likely first

  1. Failed transmission fan relay (open coil or welded contacts)
  2. Open or shorted wiring in the relay control circuit (chafed, broken, or corroded wires)
  3. Corroded or loose electrical connectors at the relay, TCM, or fan motor
  4. Defective transmission fan motor drawing excessive current or open circuit
  5. Faulty transmission control module (TCM) driver circuit
  6. Blown fuse or poor ground connection for the relay coil or fan motor

How to diagnose and fix it

  1. Verify the code with a scan tool and check for any related codes in the TCM and other modules
  2. Inspect the transmission fan relay, fuse, and wiring for obvious damage, corrosion, or loose connections
  3. Test the relay by swapping it with a known-good identical relay or performing a resistance and click test
  4. Disconnect the fan motor and check for open or shorted windings using a multimeter
  5. Check the control circuit from the TCM to the relay for continuity and short to ground or power
  6. If the circuit tests good, suspect the TCM; perform pinpoint tests according to the factory service information before replacement
  7. Clear the code and verify the repair by running the fan command with a scan tool and test-driving under conditions that activate the fan

Don't overlook the relay ground or TCM driver

  • A common oversight is assuming the relay itself is at fault when the actual problem is a corroded ground connection for the relay coil, which can mimic an open circuit.
  • The transmission fan may only operate under high fluid temperature conditions, so a faulty circuit might not show symptoms during normal driving and the code may be the only clue.
  • A shorted fan motor can damage the relay or TCM driver over time, so always test the motor when replacing a failed relay.
  • Some Chrysler models use a solid-state fan control module instead of a conventional relay, and the code can set for faults in that module even though the definition mentions a relay.
  • The TCM may set P1479 if the relay control circuit is open, but a short to voltage can also set it; always check for both open and short conditions.

Can I keep driving with P1479?

You can generally drive the vehicle with this code, but avoid heavy loads or towing until repaired because the transmission fan may not activate and fluid overheating can lead to internal damage. Monitor transmission temperature if possible and repair promptly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for Chrysler vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage