Note On Intermittents
WARNING: This page is about a different car, the 1990 Cadillac Seville and 1990 Cadillac Eldorado. However, it is still accessible from the selected car via links, so may be relevant.
If Code EO21 is intermittent, manipulate related wiring, while observing ECM parameter ED01. Check TPS connector for shorts to voltage. Cycle TPS through its travel and tap on TPS with a pencil to test for intermittent operation. If fault is induced, parameter will skip to high throttle angle. If wiring and connectors are okay, substitute a known good TPS sensor and retest.