PCM POWER & GROUND CHECK Ground Circuits 1. Using an ohmmeter, check for continuity to ground at PCM ground terminals. See CONTROL MODULE CONNECTOR TERMINAL IDENTIFICATION . See Fig. 1 - Fig. 4 . Resistance should be zero ohms. If not, repair open to ground. 2. Using a voltmeter, connect negative lead of a voltmeter to a good ground. Backprobe positive lead of voltmeter to each ground terminal. With vehicle running, voltmeter should indicate less than one volt. If voltmeter reading is more than one volt, check for open, short to voltage, corrosion or loose connection on ground circuit. Power Circuits 1. Using a voltmeter, check for battery voltage between PCM continuous power terminal(s) and ground. See CONTROL MODULE CONNECTOR TERMINAL IDENTIFICATION . See Fig. 1 - Fig. 4 . If battery voltage is not present, check for open fuse or fusible link. If okay, check for open in wire between PCM terminal and power source. 2. Turn ignition switch to RUN position. Using a voltmeter, check for battery voltage between PCM 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 terminal. If wiring is okay, check for a defective ignition switch. 3. Connect voltmeter between ground and PCM 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. 4. If voltage is not present, check CRANK fuse or fusible link between ignition switch and PCM terminal. If fuse or fusible link is okay, check for an open in wire between ignition switch and PCM terminal, or check for a defective ignition switch. PCM Harness Resistance Turn ignition switch to LOCK position. Disconnect PCM and appropriate component harness connectors. Check for open or short circuits between appropriate PCM harness connector terminal and appropriate component harness connector terminal. See CONTROL MODULE CONNECTOR TERMINAL IDENTIFICATION . See Fig. 1 - Fig. 4 . See WIRING DIAGRAMS article. If harness is open or shorted, repair as necessary. NOTE: To identify circuits referenced in the following ground and power tests, see WIRING DIAGRAMS article. Page 1 of 1 SYSTEM & COMPONENT TESTING -2000 Chevrolet Blazer 3/22/2009
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Sunday, March 22nd, 2009 AT 10:57 AM