Symptom Checks

Check the following items:

• For fast idle concern, turn ignition switch to OFF position. Turn ignition switch to ON position. Using scan tool, select TP V and TPREL PIDs from PID/DATA MONITOR & RECORD menu. Observe TP V and TPREL PIDs while wiggling TP sensor circuits. At vehicle start, TPREL PID value will begin at about 1.25 volts and count down to the lowest TP V value read since engine start-up. If TP V value goes below normal range, then increases again, TPREL will set to the lower voltage. If TP V is about .04 volt more than TPREL value at closed throttle, PCM will go into part throttle mode. Check for loose or worn throttle plates. If no concern is found, go to TEST Z, step 1)  under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - CNG & GASOLINE article and check for intermittent faults.
• Check air intake system. Go to TEST HU, step 1)  under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - CNG & GASOLINE article. If air intake system is okay, go to TEST Z, step 1)  under SYSTEM TESTS in SELF-DIAGNOSTICS - EEC-V - CNG & GASOLINE article and check for intermittent faults.