Coping With Intermittant Malfunctions

How To Cope With Intermittent Malfunctions
Most intermittent malfunctions occur under certain conditions. If those conditions can be identified, the cause will be easier to find.

To Cope With Intermittent Malfunction
1. Ask the customer about the malfunction. Ask what it feels like, what it sounds like, etc.. Then ask about driving conditions, weather, frequency of occurrence, and so on.
2. Determine the conditions malfunction occurs from the customer's responses. Typically, almost all intermittent malfunctions occur from conditions like vibration, temperature and/or moisture change, poor connections. From the customer's replies, it should be reasoned which condition is influenced.
3. Use simulation test. In the cases of vibration or poor connections, use the simulation tests below to attempt to duplicate the customer's complaint. Determine the most likely circuit(s) and perform the simulation tests on the connectors and parts of that circuit(s). Be sure to use the inspection procedures provided for diagnostic trouble codes and trouble symptoms.
For temperature and/or moisture conditions related intermittent malfunctions, using common sense, try to change the conditions of the suspected circuit components, then use the simulation tests below.
4. Verify the intermittent malfunction is eliminated. Repair the malfunctioning part and try to duplicate the condition(s) again to verify the intermittent malfunction has been eliminated.

Bend, Pull and Twist test:

Simulation Tests
For these simulation tests, shake, then gently bend, pull, and twist the connector, wiring and part of each of these examples to duplicate the intermittent malfunction.

- Shake the connector up-and-down, and right-and-left
- Shake the wiring harness up-and-down, and right-and-left
- Vibrate the part or sensor

NOTE: In case of difficulty in finding the cause of the intermittent malfunction, the data recorder function found in many scan tools is effective.