P0694 sets when the PCM detects that the Fan 2 control circuit is stuck at a higher‑than‑expected voltage, indicating a short to battery power or an open ground side. This usually means the fan is not being turned on/off as commanded, which can lead to engine overheating or excessive fan operation.
A damaged wire or connector in the fan 2 control circuit can short to a power source, pulling the circuit high and triggering the code.
If the relay that supplies power to the fan is stuck closed, the control line can read high even when the PCM attempts to ground it.
An internal short within the fan motor can feed battery voltage back onto the control line, causing the high condition.
Moisture or corrosion at the fan connector can create a path that pulls the control circuit up to battery voltage.
A defective low‑side driver inside the PCM can fail to ground the circuit, but this is a rare cause and should be investigated only after other wiring and components are ruled out.
No. PCM failure is an uncommon cause of this code. In most cases the problem is a wiring short, a faulty relay, or a bad fan motor. The PCM should be tested only after the simpler components have been ruled out.
A faulty temperature sensor may cause the fan to run incorrectly, but it does not create a high‑voltage condition on the control circuit. P0694 is specifically an electrical circuit issue.
If the fan stays on continuously the engine should stay cool, but you may experience a drained battery. If the fan does not run at all, the engine can overheat quickly, so the vehicle should be repaired promptly.
The PCM monitors the voltage on the control line; even if the fan runs, a short to power can keep the line high, causing the code to set while the fan still receives power through another path.