Diagnostic Aids

An intermittent problem can be caused by misrouted harness, rubbed-through wire insulation or broken wire inside insulation. Also, check for vacuum or PCV system leaks, incorrect PCV valve, engine oil dipstick not fully seated or engine oil filler cap loose or missing.

1. Perform On-Board Diagnostic (OBD) System Check. See BASIC DIAGNOSTIC PROCEDURES article. Go to next step.
2. Turn ignition off. Disconnect MAF sensor harness connector. Connect test light between MAF sensor connector 12-volt signal circuit terminals "C" (Black/Yellow wire) and "B" (Black/Blue wire). Turn ignition on, with engine off. If test light comes on, go to step  6. If test light does not come on, go to next step.
3. Turn ignition on, engine off. Using DVOM, check 12-volt signal circuit at MAF sensor connector terminal "C" (Black/Yellow wire) for correct voltage. If about 11.5-12.5 volts are present, go to step  5. If about 11.5-12.5 volts are not present, go to next step.
4. Turn ignition off. Check 12-volt signal circuit for an open circuit or short circuit to ground. Repair circuit as necessary.
5. Check MAF sensor ground circuit for an open circuit or short circuit to voltage. Repair circuit as necessary.
6. Turn ignition off. Check MAF sensor signal circuit between PCM and MAF sensor for an open circuit, short circuit to ground, or short circuit to voltage. Repair circuit as necessary. If circuit is okay, go to next step.
7. Reconnect MAF sensor connector. Connect scan tool. Place transmission in Park or Neutral and apply parking brake. Start and idle engine. Select MAF parameter on scan tool. If scan tool displays 4-7 g/s, go to next step. If scan tool does not display 4-7 g/s, go to step  9.
8. Observe scan tool while increasing engine RPM to its upper limit. If scan tool displays 25-40 g/s, go to step  10. If scan tool does not display 25-40 g/s, go to next step.
9. Replace MAF sensor. Verify system operation.
10. Replace PCM. Verify system operation.