This code indicates the engine computer detected a problem with the electric cooling fan's performance. Specifically, a 'rationality check' failed, meaning the computer commanded the fan on but the engine temperature or A/C pressure did not react as expected.
The internal brushes or windings of the fan motor fail, preventing the fan from spinning even when power is supplied.
A blown fuse or defective relay prevents power from reaching the fan motor when commanded by the computer.
Corroded, broken, or shorted wiring in the fan control circuit disrupts the signal or power flow to the fan.
A skewed sensor provides incorrect temperature data, causing the computer to misjudge the engine's actual cooling needs.
On vehicles with a separate solid-state fan control module, the module can fail and prevent proper fan operation.
The engine computer itself has an internal driver failure and cannot properly command the fan, though this is extremely rare.
No. Drivers are frequently told to replace the PCM for this code, but that is almost always incorrect. The actual cause is almost always a failed fan motor, relay, or wiring issue. The PCM is the last thing to suspect.
It means the engine computer monitors whether the cooling system reacts correctly when the fan is commanded on. If the engine temperature does not drop or the A/C pressure does not stabilize when the fan is supposed to be running, the computer determines the fan is not doing its job rationally.
It can be risky. If the cooling fan is inoperative, the engine may overheat in traffic or at low speeds, which can cause severe engine damage. The A/C will also likely stop working at idle to protect the system from high pressure.
The cooling fan is required to pull air through the A/C condenser when the vehicle is moving slowly or stopped. If the fan is not working, the A/C system cannot release heat, causing the system to shut down to prevent pressure damage.