I checked that car service checks many different parts like engine oil, filters, lights, brake, etc. I would assume they will tell you if something is not working. But will I be told also why something is not working? i.e. should I also expect them to diagnose the problem?

For example, say it is quite obvious that my tail lights do not light up, if I bring my car in for service, besides being told what I already know, will they also try to find out why the lights are not working (fuse, bulb, wire, socket, switch, software, etc.) as part of the service? Or diagnosing is always something extra?

3 Answers 3


If the fault just involves changing a bulb and that is an easy task then they may just do it.

However, if the fault requires time trouble-shooting and many electrical faults can take a LOT of time to resolve then good garages will contact you to make you aware so that you agree to the extra cost that will be incurred.

My garage does exactly that - if the increase is small then they go ahead, but if it looks to be significant then they will ring or text me.

It is also normal for them to give an explanation of what the issue was - and since I was in the trade it can be both short and detailed as the technical terms are understood.

  • Yes but that means they have to do something first before they can rule out if it was not as simple as replacing a bulb, right? So would they at least try to take out the old bulb and plug in a test bulb in a basic service? Nov 9, 2021 at 11:02
  • @user1589188 "If the fault just involves changing a bulb and that is an easy task then they may just do it."...
    – Solar Mike
    Nov 9, 2021 at 11:04
  • The question was "how far would they go to determine if its just a matter of changing a bulb but not something else"? Nov 10, 2021 at 1:20
  • @user1589188 Then re-read paragraph 2.
    – Solar Mike
    Nov 10, 2021 at 6:30

It all depends on what you mean by "bring my car in for service" here. If you have a specific problem, say it's running rough, I would expect the shop to diagnose that problem and fix it. Other things, not so much.

A good mechanic, however, will evaluate other possible issues and make recommendations. Things, especially safety-related, should be given a quick look. Lights, brakes, exhaust system, suspension components should be looked at.

But is any mechanic going to exhaustively inspect every system and part on a car as a part of a routine service visit? Not likely!

This is why I am always suspicious when I see an ad that says "just gone through by a mechanic". What does "gone through" mean? I believe that for the most part it starts, moves, steers, and stops. Beyond that, you're on your own.

  • Thanks. I meant exactly some routine service, non-specific ones. Nov 10, 2021 at 1:21

Some mechanics and dealers do a thorough check on the entire car when it is in for service and discover problems that the owner of the car might not have known about. This ends up saving you a lot of time/money later and can prevent parts getting completely damaged when a small fix would have solved such issues. Seek out such garages.

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