Ignition Control (IC) Timing Advance System
- A malfunction in the IC circuit (formerly referred to as the EST circuit) should set a related diagnostic trouble code. Start engine and warm to operating temperature. On vehicles equipped with a manual transmission, increase engine speed to about 2000 RPM. On vehicle equipped with an automatic transmission, slightly increase idle speed.
- On all vehicles, ground "test" terminal "B" of ALDL connector. See Fig 1. A noticeable change in engine speed should occur. If no change occurs, see DIAGNOSTIC CIRCUIT CHECK in BASIC TESTING
article in this section.
Courtesy of GENERAL MOTORS CORP.