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Home >> GMC >> 1997 >> Forward Control 6.5 F >> Repair and Diagnosis >> External Pages >> Different car >> Section 39 (Engine Controls - System/Component Tests - 5.7L.) >> Computerized Engine Controls >> Control Unit >> Power Circuits
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Power Circuits

WARNING: This page does not describe the selected car, but rather 16 other vehicles, including the 1996 GMC Yukon, 1996 GMC Vandura Special, 1996 GMC Vandura, 1996 GMC Suburban, and 1996 GMC Savana Special. However, it is still accessible from the selected car via links, so may be relevant.
  1. Using a voltmeter, check for battery voltage between ECM/PCM/VCM continuous power terminal(s) and ground. If battery voltage is not present, check for blown fuse or open fusible link. If okay, check for open in wire between ECM/PCM/VCM terminal and power source.
  2. Turn ignition on. Using a voltmeter, check for battery voltage between ECM/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 ECM/PCM/VCM terminal. If okay, check for a defective ignition switch.
  3. Connect voltmeter between ground and ECM/PCM/VCM starter (crank) signal terminal. On vehicles with manual transmission/transaxle, depress clutch pedal. Turn ignition switch to START position. Battery voltage should be present ONLY when ignition switch is in START position.
  4. If voltage is not present, check CRANK fuse or fusible link between ignition switch and ECM/PCM/VCM terminal. If fuse or fusible link is okay, check for an open in wire between ignition switch and ECM/PCM/VCM terminal, or check for a defective ignition switch.
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