What is OBD2 Code P1485 on a Chrysler Vehicle?
OBD2 Diagnostic Trouble Code (DTC) P1485 is a manufacturer-specific code for Chrysler, Dodge, Jeep, and Ram vehicles. Its generic definition is “Fan Control Relay Circuit.” This code is stored in the Powertrain Control Module (PCM) when it detects an irregularity in the electrical circuit controlling the primary engine cooling fan relay. The PCM monitors the control circuit for the relay. If the voltage expected at the PCM pin does not match the commanded state (e.g., the PCM commands the fan ON but sees a voltage indicating the circuit is open or shorted), it will set P1485 and often illuminate the check engine light.
This is a critical code because a malfunctioning cooling system can lead to severe engine overheating, resulting in costly damage like a warped cylinder head or a blown head gasket. Addressing P1485 promptly is essential for vehicle health and safety.
Common Symptoms of a P1485 Code
When code P1485 is active, you will likely experience one or more of the following symptoms. The most obvious issues relate directly to the cooling fan’s operation.
Primary Symptom: Cooling Fan Inoperative
The most direct symptom. The engine cooling fan does not turn on at all, regardless of engine temperature or when the A/C is activated. You may notice the fan remains still even when the temperature gauge climbs into the hot zone.
Engine Overheating, Especially at Idle
Without the fan pulling air through the radiator at low speeds or during idle, engine coolant temperature will rise rapidly. Overheating may seem to resolve once you’re driving at highway speeds due to increased airflow.
Check Engine Light is Illuminated
The PCM will illuminate the Malfunction Indicator Lamp (MIL), commonly known as the check engine light, upon detecting the fault. The code P1485 will be stored in memory.
Poor A/C Performance in Traffic
The cooling fan is typically commanded to run when the air conditioning system is engaged to help cool the condenser. A faulty fan circuit will cause poor A/C cooling efficiency, particularly when the vehicle is stationary.
Possible Fan Stuck On
In some circuit failure scenarios (like a short), the cooling fan may run continuously as soon as the ignition is turned on, draining the battery if the engine is off.
Root Causes of Chrysler P1485 Code
Diagnosing P1485 requires a systematic approach, starting with the simplest and most common causes. The fault lies within the low-current control side of the fan circuit that the PCM manages.
Faulty Cooling Fan Relay
The relay itself is the most frequent culprit. Relays have internal contacts that can burn out or a coil that can fail, preventing the PCM’s signal from switching the high-current circuit for the fan motor.
- Location: Typically found in the Power Distribution Center (PDC) under the hood. Consult your owner’s manual or the PDC lid diagram for the exact location (often labeled “Fan Relay” or “Radiator Fan Relay”).
Damaged Wiring or Connectors
The wiring harness between the PCM, the relay, and the fan motor can suffer from:
- Chafing or rubbing against sharp edges, causing shorts or open circuits.
- Corrosion at connectors, especially in the PDC or at the fan motor plug.
- Rodent damage chewing through wire insulation.
Failed Cooling Fan Motor
A seized or burnt-out fan motor can draw excessive current, which can damage the relay and its control circuit. While a direct motor failure might set other codes (like P1491 for fan performance), it can contribute to P1485 circuit issues.
Blown Fuse
Always check the high-amperage fuse that protects the fan motor circuit. It is usually located in the same PDC as the relay. A blown fuse is often a symptom of another problem (like a shorted motor), not the root cause itself.
Faulty Powertrain Control Module (PCM)
This is the least likely cause. A failure of the internal driver circuit within the PCM that controls the relay coil is rare. It should only be suspected after all other components and wiring have been thoroughly tested and verified as good.
Step-by-Step Diagnostic & Repair Guide
Follow this logical diagnostic sequence to accurately identify and resolve the P1485 fault. Safety First: Ensure the engine is cool before working, and disconnect the battery negative terminal when probing relays or wiring.
Step 1: Preliminary Checks & Code Verification
Begin by using an OBD2 scanner to confirm P1485 is present and active. Clear the code and perform a test drive. If it returns immediately, the fault is hard (current). If it only returns under certain conditions (like with A/C on), it may be intermittent. Visually inspect the fan for physical obstruction and listen for any unusual noises when attempting to activate it via a scan tool.
Step 2: Relay and Fuse Inspection
Locate the cooling fan relay and fuse in the PDC. Swap the fan relay with an identical relay in the box (e.g., horn relay) to see if the problem moves. Visually inspect and test the fuse for continuity with a multimeter. Check for corrosion or loose pins in the relay socket.
Step 3: Active Command Testing with a Scan Tool
This is a crucial step. Using a bi-directional scan tool, access the PCM’s output controls and manually command the cooling fan ON and OFF. Listen for the relay click and the fan motor operation.
- If the fan runs when commanded: The circuit is currently functional. The code may be intermittent due to a wiring issue.
- If the relay clicks but fan doesn’t run: The problem is likely downstream: bad fan motor, high-current circuit fault, or ground.
- If no relay click occurs: The problem is in the control circuit: wiring to/from PCM, the relay coil, or the PCM itself.
Step 4: Electrical Circuit Testing with a Multimeter
If the relay doesn’t click during active commands, perform voltage and resistance checks (with the relay removed):
- Check for constant battery voltage at one of the relay coil terminals (85 or 86).
- Check for switched ground from the PCM at the other coil terminal when the fan is commanded ON (this should show near 0 volts).
- Check for continuity and resistance in the wires between the PCM connector and the relay socket for opens or shorts to power/ground.
Step 5: Fan Motor and Final Circuit Verification
Test the fan motor directly by applying 12 volts and ground to its terminals (briefly). If it doesn’t run, the motor is faulty. Also, verify the motor’s ground connection is clean and tight. Once the faulty component is identified (relay, wiring, motor), replace it, clear the code, and test the system’s operation through a full heat cycle and A/C activation.
Conclusion: Ensuring a Reliable Repair
Code P1485, while serious, is typically straightforward to diagnose with a methodical approach. The cooling fan relay is the most common point of failure in Chrysler, Dodge, Jeep, and Ram vehicles. Always remember that a blown fuse or a failed fan motor can be the underlying cause that led to the relay circuit code. After completing the repair, use your OBD2 scanner to clear the code and confirm it does not return. A successful repair will restore proper cooling system function, prevent engine overheating, and ensure your A/C works efficiently, especially in stop-and-go traffic. If you are uncomfortable with electrical diagnostics, seeking a professional technician is a wise investment to protect your engine from severe damage.