Power Circuits
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 1998 GMC Suburban, 1998 GMC Pickup, 1998 GMC Cab & Chassis, 1998 GMC C3500 HD, and 1998 Chevrolet Suburban. However, it is still accessible from the selected car via links, so may be relevant.
- Using a voltmeter, check for battery voltage between PCM/VCM continuous power terminal(s) and ground. See POWERTRAIN CONTROL MODULE (PCM) table. If battery voltage is not present, check for blown fuse or open fusible link. If okay, check for open in wire between PCM/VCM terminal and power source.
- Turn ignition switch to RUN position. Using a voltmeter, check for battery voltage between PCM/VCM ignition power terminals and ground. If battery voltage is not present, check IGN fuse. If fuse is okay, check for an open in wire between battery and ignition switch, and between ignition switch and PCM/VCM terminal. If okay, check for a defective ignition switch.
- Connect voltmeter between ground and PCM/VCM starter (crank) signal terminal. On vehicles with manual transmission/transaxle, depress clutch pedal. On vehicles with automatic transmission/transaxle, position gear shift lever in Park. On all vehicles, turn ignition switch to START position. Battery voltage should be present ONLY when ignition switch is in START position.
- If voltage is not present, check CRANK fuse or fusible link between ignition switch and PCM/VCM terminal. If fuse or fusible link is okay, check for an open in wire between ignition switch and PCM/VCM terminal, or check for a defective ignition switch.