Diagnostic Aids

Check for damages or sticking throttle plate or IAC valve. A throttle valve place 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. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connection.

If DTC cannot be duplicated, the information included in the FAIL RECORDS data can be useful in determining vehicle mileage since DTC was last set. If it is determined that DTC is intermittent, performing DTC P1121  or P1122 diagnosis may isolate cause of fault.