Programming the TDC Offset
WARNING: This page is about a different car, the 2002 GMC C3500 HD and 2002 Chevrolet C3500 HD. However, it is still accessible from the selected car via links, so may be relevant.
The PCM will automatically activate the TDC offset program when the engine coolant is more than 77°C (170°F). If the PCM is not programmed with a TDC offset, a DTC P1214 will set.