Diagnostic Aids

Check for damaged or sticking throttle plate or IAC valve. A throttle valve plate or IAC valve that allows too much airflow while throttle should be closed may cause a high idle and DTC P0121 to set.

A skewed MAP signal or faulty MAP sensor or an incorrect MAP signal may cause PCM to incorrectly calculate the predicted TP sensor value during high engine load situations. Check for an unusually low MAP reading. This condition can cause DTC to set.

Check for poor connections at PCM. Check harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connection.