Powertrain Control Module
WARNING: This page does not describe the selected car, but rather 15 other vehicles, including the 2003 Hummer H2, 2003 GMC Yukon XL, 2003 GMC Yukon, 2003 GMC Sierra, and 2003 GMC Savana. However, it is still accessible from the selected car via links, so may be relevant.
The PCM has a "learning" ability which allows it to make minor corrections for fuel system variations. PCM is located on left front of engine compartment, behind radiator. See Fig 1. If battery power is interrupted, a vehicle performance change may be noticed. PCM module corrects itself, and normal performance returns if vehicle is allowed to "relearn" optimum control conditions. "Relearning" occurs when vehicle is driven at normal operating temperature under part throttle, moderate acceleration and idle conditions.