Tachometer Test
WARNING: This page is about a different car, the 1994 Buick Park Avenue. However, it is still accessible from the selected car via links, so may be relevant.
With engine running, measure voltage at tachometer input connector White wire. Voltmeter should indicate 1-10 volts and should vary with engine RPM. If voltmeter reading is not as specified, check White wire for open circuit. If White wire is okay, ignition system is faulty. If voltage reading is correct, replace tachometer or IPC, as necessary.