To be fair ‘warning light is lit’ is all the mechanic needs to know in a lot of circumstances.
Most of the time, the warning light comes on because the engine’s computer has logged an error code. The mechanic just plugs his code reader in to find out what the code is and then looks up what it means. And ~90% of the time, the engine’s computer does a pretty good job of telling the mechanic what’s wrong.
(For example, if it gives a code for “Cylinder #4 misfire”, then the mechanic knows he should probably check the spark plug and coil for cylinder #4. And if those seem fine, get out the compression tester and test the compression of cylinder #4. And without any additional information from the customer besides ‘warning light is lit’, that’s probably enough for him to find the cause of the problem.)
To be fair ‘warning light is lit’ is all the mechanic needs to know in a lot of circumstances.
Most of the time, the warning light comes on because the engine’s computer has logged an error code. The mechanic just plugs his code reader in to find out what the code is and then looks up what it means. And ~90% of the time, the engine’s computer does a pretty good job of telling the mechanic what’s wrong.
(For example, if it gives a code for “Cylinder #4 misfire”, then the mechanic knows he should probably check the spark plug and coil for cylinder #4. And if those seem fine, get out the compression tester and test the compression of cylinder #4. And without any additional information from the customer besides ‘warning light is lit’, that’s probably enough for him to find the cause of the problem.)