Some of the hardest problems to solve are the ones that disappear when you take the car to a workshop. A warning that appears once a week, a noise only on cold mornings or a hesitation that happens only on the motorway can be very frustrating. Good documentation is the key to solving them.
Why intermittent faults are difficult
When a fault is not present, a technician may not be able to reproduce it, and fault codes may have been cleared or overwritten. The more details you collect, the easier it is for members and professionals to narrow down the cause.
What to record every time it happens
Keep a simple note on your phone with:
- Date and time.
- Outside temperature and weather: cold, hot, wet or dry.
- Engine temperature: just started, warming up or fully warm.
- Driving situation: idling, accelerating, cruising, braking, turning or parking.
- Speed and gear, if relevant.
- Exact warning messages, word for word, or a photo of the instrument cluster when it is safe and the car is stopped.
- What made it go away: restarting, waiting or nothing.
Patterns to look for
After several notes, patterns often appear. A problem only in wet weather can point to moisture in a connector. A fault after a long drive can relate to heat. A problem only when the battery is weak can affect many electronic systems at once.
Read the fault memory soon after
If you have a diagnostic tool, read the fault memory as soon as possible after the event, before you clear anything. Write down the codes and descriptions. If you visit a workshop, ask them to save a copy of the fault report.
Video and sound
For noises and drivability issues, a passenger can record a short video. Never film while you are driving. Recordings help members identify rattles, whines and knocks.
What to post
When you start a topic, include your model, engine, mileage, your notes, any fault codes and what has already been checked or replaced. Update the topic when you find the cause, because your solution could help another member with the same intermittent fault.