Steps in Isolating the Problem
- Use Test Modules.
- Perform electrical tests with the DISplus Measurement System or a DVOM.
- Consult fault charts in Repair or Diagnostic Procedures Manuals.
- Control Module Self Diagnosis.
- Use appropriate special tools (e.g. battery draw tester, tank leakage adapters, breakout boxes, etc.).
- Substitute a known good part.
Workshop Hint
If a TEST PLAN is not available:
- Think about the system in its entirety.
- Be sure the normal operation is understood.
- Develop a PLAN.
- Use all available resources.
- Don't try to diagnose the entire system at once, break it into manageable chunks.
- Check the easy things first. It would waste time to install the breakout boxes to find a bad bulb.
If a TEST PLAN is available:
- Do not skip steps.
- Never assume results without doing a step.
- Recheck your work.