Rough idle, misfires, stalling, loss of power, or a check engine light that will not go away.
A code tells you where to look. It does not tell you what to buy. We scan the codes and then actually test the circuit or component the code points at.
That takes longer than throwing a sensor at it, and it is the difference between a repair that holds and one that brings you back in three weeks.
If a repair does not make economic sense on a particular vehicle, we will tell you that too.