P0694 Fan 2 Control Circuit High
OBD-II Trouble Code Technical Description
Cooling Fan 2 Relay Control Circuit High
What does that mean?
This is a generic powertrain diagnostic trouble code (DTC) applicable to most 1996-newer vehicles. Specific repair steps can vary from make/model.
The fans that are used to cool the engines radiator are run by electric motors. These motors are turned on and off by the powertrain control module (PCM) according to the readings from the engine coolant temperature sensor (ECT). In other words when the ECT reaches a predetermined temperature the PCM turns the fans on. Then when the ECT cools to a predetermined temperature the PCM turns the fans off.
The PCM controls the cooling fans by sending a ground signal to the cooling fan relay. The voltage on the signal circuit is high, around battery voltage, when not commanded on (not grounded). The opposite is true when commanded on (grounded), the voltage is somewhere near zero. DTC P0694 is set when the PCM senses that the voltage remains high when the cooling fan 2 is commanded on.
Symptoms & Severity of Code
Symptoms of a P0694 code may include:
The possibility of the engine overheating due to non-operational cooling fans is very probable so caution should be used if driving the vehicle when the conditions to set this DTC are present. It should be repaired as soon as possible.
Causes
Potential causes for this code to set are:
Diagnostic and Repair Procedures
In my experience a faulty cooling fan relay is the most common cause of this DTC. A simple way of checking the relay is locate it and visually check for other relays that are identical to it, and then switch the two relays. Clear the codes and run the vehicle. If the code does not return then replace the relay. If it does return then suspect a possible PCM issue.
Note: Be absolutely sure that the relay you are switching is identical in every way. Installing the incorrect relay could do damage to the PCM. Nissan in particular has relays the appear to be the same other than color and will plug into the same socket but are different and will damage the PCM
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"Delete Error Code Permanently, Disable DTC Error Code Function for p0694 in the ECU"
In extreme cases, we even have the option to permanently remove the specific DTC p0694 and disable the function of the specific error code in the ECU. All other fault code functions will then continue to work to protect the engine. This is different from clearing an error code with a diagnostic device. We have the option to permanently remove the function of the specific error code, so that it never comes back. Also emergency running that occurs on the specific error code can be solved in most cases.
Of course we prefer to first try to solve the cause of the error code, but sometimes the only solution is to permanently disable the DTC function of p0694.
