Set Condition
WARNING: This page is about a different car, the 1995 Pontiac Bonneville, 1995 Oldsmobile Eighty-Eight, and 1995 Buick LeSabre. However, it is still accessible from the selected car via links, so may be relevant.
Code P0401 will set when PCM does not detect a decrease in engine speed of at least 50 RPM for 6 out of 8 tests. Once 3 tests are run during an ignition cycle, PCM will not run any further flow tests until next ignition cycle. Thus, 3 or more ignition cycles will be necessary to set Code P0401.