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 Articles.
• 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 Hints: 

If a TEST PLAN  is not available for a particular situation do the following:

• 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.

When following a TEST PLAN:

• DON'T  Skip steps.
• NEVER  assume results without doing a step.
• Recheck your work.