Automotive Service Excellence (ASE) A6 Electrical/Electronic SystemsGeneral Electrical/Electronic System DiagnosisMedium
A technician is diagnosing a vehicle with an intermittent issue where the engine occasionally stalls or hesitates. The technician suspects a poor connection at a multi-pin connector in the engine compartment. Which diagnostic tool or technique would be MOST effective for identifying this type of intermittent fault?
- AA voltage drop test performed by wiggling the connector while the engine is running.
- BApplying dielectric grease to all connector pins and retesting.
- CA continuity test with the connector disconnected.
- DMeasuring the resistance of the individual pins with an ohmmeter.
Show answer & explanationAnswer & explanation
Correct answer: A. A voltage drop test performed by wiggling the connector while the engine is running.
An intermittent connection often manifests as a voltage drop when the connection is disturbed or under load. Performing a voltage drop test while wiggling the connector (also known as a 'wiggle test' or 'shake test') can reveal a momentary increase in resistance, indicated by a fluctuating or increasing voltage drop, pinpointing the faulty connection.
Why the other options are wrong
- B. Applying dielectric grease is a preventative measure, not a diagnostic one, and should be done after identifying and repairing the fault.
- C. A continuity test with the connector disconnected will only show if the circuit is completely open, not an intermittent poor connection under load.
- D. Measuring static resistance might not reveal an intermittent connection that only occurs under vibration or load.
Wiggle Test (Voltage Drop)
A diagnostic technique involving applying physical movement or vibration to a suspected intermittent connection while monitoring voltage drop to identify the fault.
- Performed with the circuit under load.
- Monitors for fluctuating or increasing voltage drop.
- Effective for intermittent open circuits or high resistance problems.
Memory trick: Wiggle and Watch the Drop: The Intermittent's Secret Revealed.