Diagnostic Aids

An intermittent problem can be caused by:

• Misrouted harness, rubbed-through wire insulation or broken wire inside insulation.
• A plugged or restricted air intake. A wide-open acceleration from a stop should cause MAF parameter on scan tool to increase from 3-6 grams/sec. at idle to 100 grams/sec. when transmission shifts from first to second gear.
• Poor connection at PCM. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal connection. Inspect wiring harness for damage.

If harness appears to be okay, use scan tool to observe sensor readings while moving connectors and harnesses. A change in display will indicate location of fault. If DTC can not be duplicated, reviewing scan tool FAILURE RECORDS data can be useful in determining mileage and frequency of DTC occurrence.