Circuit Description
WARNING: This page is about a different car, the 1998 Pontiac Bonneville, 1998 Oldsmobile Regency, 1998 Oldsmobile LSS, 1998 Oldsmobile Eighty-Eight, and 1998 Buick LeSabre. However, it is still accessible from the selected car via links, so may be relevant.
PCM tests Exhaust Gas Recirculation (EGR) valve by momentarily commanding valve on while monitoring engine MAP. PCM will illuminate MIL and store DTC P0401 if expected increase is not seen under certain conditions during deceleration.
Conditions required to set DTC are:
- No ECT, IAT, MAP, or TP sensor DTCs set.
- No misfire, linear EGR (pintle position) or vehicle speed sensor DTCs set.
- BARO is greater than 10 psi (0.7 kg/cm2 ).
- ECT greater than 180°F (80°C).
- Vehicle speed greater than 25 MPH.
- Engine speed is 800-1400 RPM.
- IAC position steady.
- TP angle less than one percent.
- Commanded state of A/C relay is steady.
- MAP changes monitored during EGR flow test indicate insufficient EGR flow.