P0693Fan 2 Control Circuit Low
The control circuit for cooling fan 2 is reading lower voltage than expected, usually from a short to ground or excessive current in the fan 2 circuit.
Definition
On vehicles with multiple cooling fans or a two-speed fan arrangement, the PCM controls fan 2 through its own relay or driver and monitors the control line. P0693 sets when the circuit voltage is below the expected value for the commanded state, indicating a short to ground or an overloaded driver. Fan 2 typically handles high-speed or A/C-demand cooling, so symptoms include overheating under load, A/C pressure spikes at idle, and an illuminated MIL.
Common causes
- Fan 2 control wiring shorted to ground
- Shorted fan 2 relay coil
- Fan 2 motor pulling excessive current from worn bearings or shorted windings
- Corroded or water-damaged connector at the fan or relay
- Failed fan control module
- Faulty PCM driver
Common misdiagnoses
- Both fan motors replaced when only wiring or a relay is faulty
- A/C pressure sensor or compressor blamed for high-side pressure complaints caused by the dead fan
- PCM replaced without isolating the short
Troubleshooting steps
1.Command fan 2 independently with a scan tool
Many systems allow separate low/high or fan 1/fan 2 commands — verify which output is dead before touching parts.
2.Measure control-circuit voltage
A control line stuck near 0 V regardless of command indicates a short to ground between the PCM and relay.
3.Test the fan 2 relay
Check coil resistance against the fan 1 relay and swap relays to see if the fault follows.
4.Measure fan 2 motor current
Compare amperage to the fan 1 motor or factory spec; excessive draw indicates a failing motor loading the circuit down.
5.Isolate the harness
Disconnect the fan and relay, then check the control wire for continuity to ground — any reading indicates chafed insulation to locate and repair.