Error Code P0694 is defined as Cooling Fan 2 Relay Control Circuit High. This code is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system, especially those made since 1996 up to present. Specifications on the description, diagnosis, and repairs, of course, may vary from one make and model to another.
Electric motors run the fan to cool the radiator in the engine. These motors are turned on and off by the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes), depending on the readings it gets from the ECT (engine coolant sensor). This means, when the ECT reaches a set temperature, the PCM will turn the fans on. When the ECT cools to a predetermined temperature, then the PCM turns off the fans.
The PCM controls the cooling fans by sending a ground signal to the cooling fan relay. When not commanded on (not grounded), then the voltage on the signal circuit is high, around battery voltage. The opposite is true when commanded on (grounded), the voltage is somewhere near zero. Error Code P0694 is set when the PCM senses the voltage remains high, even when the cooling fan 2 is commanded on.
Since this code affects the fan, engine overheating is the most common symptom. Non-operational cooling fan can cause the engine to overheat when driving. Thus, it’s important to be cautious when driving a vehicle with this code. Thus, it should be addressed as soon as possible.
This code can have several reasons for appearing, such as:
- Defective cooling fan 2 relay
- Blown cooling fan 2 fuse
- Defective PCM (rare)
How to Check
Faulty cooling fan relay is the most common cause of this code. A straightforward way to diagnose is to check where the relay is located and conduct a visual inspection for other relays identical to it. Then, switch the two relays on.
Next, clear the codes and then run the vehicle. If the code doesn’t return, then replace the relay. If the code returns, then you can suspect a possible problem with the PCM.
How to Fix
- Replacement of faulty fan-related components (relay, resistor, motor)
- Repair or replacement of broken, corroded, or shorted circuitry
- Replacement of cooling fan fuse
- Replacement and reprogramming of PCM
Make sure the relays you’re switching are identical in every way. Installing the wrong relay could damage the PCM. Nissan vehicles, for example, have seemingly the same relay, other than the color, and can be plugged into the same socket. However, these are very different relays and can cause damage to the PCM.
Error Code P0694 poses a relatively small issue to the vehicle if any. In most cases, the vehicle may not have any noticeable symptom. If there are symptoms, however, the engine will likely overheat, and the air conditioner may not work.