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Home › Saturn › 2000 › LS2 Standard › Repair and Diagnosis › Engine Performance › System › Engine Controls - Self-Diagnostics › Diagnostic Tests › DTC P0645: A/C Clutch Relay Circuit Open › Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
  2. Turn ignition on, with engine off. Using scan tool, command A/C relay on and off. If compressor clutch follows command, problem is intermittent. See DIAGNOSTIC AIDS . If compressor clutch does not follow command, go to next step.
  3. Check ENG CTRL 1 fuse (10-amp) located in underhood fuse/relay block. Replace fuse as necessary. Remove A/C relay from underhood fuse/relay block. Connect a test light between A/C relay cavity terminals No. 85 and 86 at fuse/relay block. Using scan tool, command A/C relay on. If test light illuminates, check for terminal tightness. Repair as necessary. If terminals are okay, replace relay. If test light does not illuminate, go to next step.
  4. Turn ignition on, with engine off. Connect test light between ground and relay cavity No. 85 at fuse/relay block. If test light illuminates, check circuit for open or for terminal tightness at connectors. Repair as necessary. If circuit and terminals are okay, replace ECM. If test light does not illuminate, repair open in underhood fuse/relay block circuit.
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