What happens when DTCs are cleared from the vehicle's computer?

When diagnostic trouble codes (DTCs) are cleared from a vehicle's computer, the malfunction indicator light (MIL) turns off. This occurs because DTCs are typically associated with faults in the vehicle's systems that trigger the MIL. Clearing the DTCs resets the system's trouble code memory, indicating that the apparent issues have been addressed or that they are no longer present.

Once the DTCs are erased, the vehicle's computer goes back to a normal operating state. In many cases, if the issue that prompted the DTCs to be stored is resolved, the MIL will remain off. However, if the underlying problem persists, the system may detect the fault again during operation, causing the MIL to turn back on in the future.

In contrast, other options reflect misunderstandings about the DTC clearing process. Resetting does not necessarily mean that all system parameters are reset, nor does it immediately trigger the MIL to turn back on without the associated underlying issue being detected. The DTCs will not reappear immediately unless the faults are still present in the vehicle's systems.