Effective Diagnostic Techniques

The following diagnostic process is critical for consistently successful diagnoses. Random methods work inconsistently and often lead to multiple repairs and the accompanying frustration.

• Understand and verify the symptom  .
  • Understanding a symptom requires understanding normal operation.
  • Duplicate the concern. Re-create the same conditions that demonstrated the original concern (road testing may be necessary).
• Determine the responsible system  .
  • Perform system tests, such as pressure tests or DTC retrieval.
• Identify the responsible component  .
  • Test the suspect component and related parts.
• Determine the root cause 
  • Examine related components (wiring faults, misalignments, incorrect adjustments) that may be the actual cause or may have caused the component failure.
  • Repair all related faults to avoid repeat failures.
  • Verify the repair has corrected the concern (and not created any new ones) using the identical conditions that demonstrated the original concern.