Q: I have a 2007 chevy impala ltz with 3 codes coming on P0121 / P1516 / P2135 ,accelerater pedal an throttle body have been replaced

Trouble Code P0121 can set if there are faults in the wiring or terminal connections to the throttle/accelerator position sensor. Circuity integrity should be checked and the output of the sensor should be viewed on a scan tool to confirm operation or, if the circuit is faulty, confirm the misoperation. P2135 can also set if the position sensor circuit is faulty, again if the circuit is open or if there is corrosion, high resistance, a short, damaged wiring or broken electrical connections. With regard to the third code, P1516, that also will set if there is any fault in the circuit. The bottom line is it is not enough for the sensor to function or be "new"; the the signal from the sensor must get to the computer and for that to happen the wiring must be pristine. Unless circuit integrity has already been confirmed relative to these three codes, a diagnostic should be performed. The relevant service to request is a Check Engine Light diagnostic. If a circuit fault is found during the diagnostic, the same mechanic who performs the diagnostic would perform the repair, right at your location. If you have further questions or concerns, do not hesitate to re-contact YourMechanic because we want you to make the most of your repair dollars and help you to get the best possible results.