Some Nissan check engine codes, also known as diagnostic trouble codes, include P1120, which indicates a fault in the secondary throttle position sensor circuit, and P1126, which indicates a fault in the thermostat function. As of 2015, another common code is P1217, indicating that the engine is overheated.
The check engine codes is diagnosed by connecting a Nissan CONSULT or OBD II scan tool to the vehicle by using the 16 pin data link connector found under the steering column. If no scan tool is available, the codes can also be checked by setting the vehicle's Engine Control Module to Diagnostic Test Mode II.
To set the ECM to Diagnostic Test Mode II, first ensure that the accelerator pedal is fully released, and then turn the ignition switch to on and wait three seconds. Once the ignition switch is on, quickly depress and fully release the accelerator pedal five times within five seconds. After the fifth time, wait seven seconds and then fully depress the accelerator pedal for approximately 10 seconds until the malfunction indicator lamp on the vehicle's instrument panel begins blinking. Once the light starts blinking, fully release the accelerator pedal and the ECM should then be in Diagnostic Test Mode II.