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Home >> Chevrolet >> 1999 >> Cavalier LS, 2.2 4 >> Repair and Diagnosis >> Body & Frame >> Body, Cab Control Systems >> MULTIFUNCTION Alarm Module >> System Tests >> Scan Tool Does Not Communicate With Class 2 Serial Data Line
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Scan Tool Does Not Communicate With Class 2 Serial Data Line

NOTE: Short to ground will cause fuse to module power feed to blow. Before performing diagnostic procedure, check for blown fuse for module. See appropriate wiring diagram in POWER DISTRIBUTION article in WIRING DIAGRAMS.
  1. Remove scan tool from Data Link Connector (DLC). Disconnect Powertrain Control Module (PCM) connector. Check for open or short to ground in power feed circuits to PCM. See appropriate wiring diagram in POWER DISTRIBUTION article in WIRING DIAGRAMS. If faulty circuit was found and repaired, go to DATA LINK COMMUNICATIONS DIAGNOSTIC SYSTEM CHECK  . If circuit is okay, go to next step.
  2. Check for open in ground circuit of PCM. See appropriate wiring diagram in GROUND DISTRIBUTION article in WIRING DIAGRAMS. If faulty circuit was found and repaired, go to DATA LINK COMMUNICATIONS DIAGNOSTIC SYSTEM CHECK  . If circuit is okay, go to next step.
  3. Check for open, short to ground or short to open in Purple wire between PCM connector C1 terminal No. 59 and DLC terminal No. 2. See appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS. If faulty circuit was found and repaired, go to DATA LINK COMMUNICATIONS DIAGNOSTIC SYSTEM CHECK  . If circuit is okay, go to next step.
  4. Replace PCM. See appropriate REMOVAL, OVERHAUL & REPLACEMENT - CARS article in ENGINE PERFORMANCE. After repairs, go to DATA LINK COMMUNICATIONS DIAGNOSTIC SYSTEM CHECK  .
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