Test Description
Number(s) below refer to step number(s) on Diagnostic Table.
- 1. The On-Board Diagnostic (OBD II) System Check prompts technician to complete some basic checks and to store freeze frame and failure records data on scan tool if applicable. This creates an electronic copy of data taken when malfunction occurred. The information is then stored on scan tool for later reference.
- 3. A visual/physical inspection should include checking following components:
- The wiring for proper connections, pinches or cuts.
- The PCM/ECM grounds for being clean and tight.
- The vacuum hoses for splits, kinks, and improper connections as shown on Vehicle Emission Information label.
- Check thoroughly for any type of leak or restriction.
- Check for air leaks at throttle body mounting area and intake manifold sealing surfaces.
- 5. When all accumulators are relatively equal, then misfire is being caused by something that affects entire engine. When they are not, then misfire is being caused by something that is specific to two or more cylinders.
- 6. Whenever misfire is not present, operating vehicle may be necessary to duplicate conditions in Freeze Frame Data in order to detect misfire. Depending on engine load, conditions may have to be maintained for up to 20 seconds. Whenever misfire accumulators start to increment, then misfire is present. A history misfire counter will store number of misfires that have occurred until DTC is cleared.
- 8. Check fuel for water, alcohol, etc.
- 9. A basic engine problem that affects all cylinders is only possibility at this point (Cam timing throttle body leak, restricted air flow, etc.).
- 11. Tests ignition system voltage output using a spark tester.
- 12. Replace any spark plugs that are worn, cracked or fouled.
- 13. Checks for voltage at ignition feed circuit.
- 18. Whenever driver circuit is shorted to ground, light will be on steady. When driver circuit is shorted to voltage or open, light will be off.
- 19. Since voltage is supplied to fuel injector on a single circuit, malfunction can only be a poor connection or open in fuel injector harness. An open before harness would result in a "Engine Cranks But Will Not Run" complaint.
- 27. Before replacing PCM/ECM, check terminals for improper mating, broken locks, or physical damage to wiring harness. The replacement PCM/ECM must be reprogrammed.