Notes on Intermittents
WARNING: This page is about a different car, the 1988 Cadillac Seville and 1988 Cadillac Eldorado. However, it is still accessible from the selected car via links, so may be relevant.
To diagnose intermittent set/coast function, turn cruise control dash switch to "ON" position and backprobe ECM pin "B4" with a voltmeter to ground. Pin "B4" should show 12 volts with "SET/COAST" switch depressed and zero volts with "SET/COAST" switch released. Cycle switch while manipulating wiring and connectors.