Conditions for Clearing the MIL/DTC

WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The PCM will turn the MIL OFF after 3 consecutive trips that the diagnostic has been run and passed.
The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
The DTC can be cleared by using the scan tool Clear DTC Information function.

Fig 1: DTC P1258 Diagnosis

Courtesy of GENERAL MOTORS CORP.