The engine control computer (ECC) generates trouble code P0507 when it senses something is wrong with the engine idle (RPM) speed. On a computer controlled throttle vehicle, such as your Nissan Maxima, there is no accelerator cable which opens or closes the throttle plate; which is used to increase or decrease engine RPM. Whenever the ECC senses the engine idle speed is different than what it has calculated to be, trouble code P0507 is triggered and the check engine light is turned on.
The likely faults for high RPM trouble code may be due to one or more of the following:
- Major or minor vacuum leak between or within engine components
- Defective intake manifold or throttle body gasket; causing a vacuum leak
- Defective or damaged EGR valve; causing a vacuum leak
- Defective PCV (positive crankcase ventilation) valve
- Failed IAC (idle air controller) or faulty IAC circuit
In order to pass the smog check it will be necessary to have a smog check repair station conduct an accurate diagnosis of your Nissan Maxima's smog check failure. Once the problems is repaired, the check engine should be reset, and the vehicle driven approximately 200-300 miles over the course of 2-3 days in order to make the "emissions monitors" ready for the smog retest.
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