Faulty fan control module or fan driver circuit giving a stuck or incorrect output; Wiring or connector fault in the fan control or speed feedback circuit, such as a short, corrosion or chafing; Fan motor fault causing it to run faster than commanded or send a wrong speed signal; Faulty coolant temperature sensor or air conditioning pressure sensor causing wrong fan demand; Fan relay stuck closed, on vehicles with relay-controlled fans; Engine control unit fault or outdated software, where a known fault is documented for that model.

P0493

Fan Overspeed.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
4: AreaAuxiliary emission controls
93: FaultThe specific fault in that area

What it means

P0493 is the generic code for a cooling fan overspeed condition. The engine control unit commands the cooling fan to a set speed or duty, but the fan speed it measures or infers is higher than commanded, or it will not drop back when requested. How the fan is controlled and monitored depends on the vehicle, so the exact set criteria vary by model and engine.

Symptoms

Cooling fan runs at full speed constantly or at the wrong times
Loud fan noise after switching off or at idle
Engine temperature reading lower than normal
Cooling fan warning or engine management light on
Air conditioning performance affected
Fan does not respond properly to temperature or air conditioning demand

Possible causes

Faulty fan control module or fan driver circuit giving a stuck or incorrect outputlikely
Wiring or connector fault in the fan control or speed feedback circuit, such as a short, corrosion or chafinglikely
Fan motor fault causing it to run faster than commanded or send a wrong speed signalpossible
Faulty coolant temperature sensor or air conditioning pressure sensor causing wrong fan demandpossible
Fan relay stuck closed, on vehicles with relay-controlled fanspossible
Engine control unit fault or outdated software, where a known fault is documented for that modelrare

How to diagnose

Read all stored and pending codes and the freeze frame data, noting coolant temperature, vehicle speed and air conditioning state when the code set
Check for related codes covering coolant temperature sensor, fan circuits or communication faults and deal with those first
Visually inspect the fan, shroud and wiring for damage, chafing, water ingress and corroded or loose connectors
Check the fan runs normally at key on and engine off, then with the engine warm, noting whether it stays on at full speed
Use a scan tool to command the fan at different speeds and compare commanded speed with actual speed data where supported
Check the coolant temperature sensor and air conditioning pressure readings for plausibility against actual conditions
Test the fan supply, earth and control signal at the connector, following the manufacturer wiring diagram for the model
Check relays, fuses and the fan control module, and look for any manufacturer software updates or service information for that model

How to fix

Repair damaged wiring or connectors in the fan control circuit
Replace the cooling fan motor or fan assembly if it is faulty
Replace the fan control module if it is confirmed faulty
Replace a faulty coolant temperature or air conditioning pressure sensor
Replace a stuck relay
Apply a manufacturer calibration update only if an outdated calibration is a documented cause for that vehicle

Can I keep driving?

Medium severity

Short journeys are usually possible, but have it checked soon. A fan stuck at full speed can drain the battery and overstrain the fan or its control unit, and the fault may also hide a cooling problem, so watch the temperature gauge and stop if it rises.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.