October 30: LEMON manuals on a temporary server, it is slow and having issues, download the manuals you need! Later in November we will switch back to the fast server.

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.