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Home › Saturn › 2002 › SL › Repair and Diagnosis › Engine Performance › System › Engine Controls - Self-Diagnostics › Diagnostic Tests › DTC P1620: Low Coolant Switch Circuit › Diagnostic Procedures

Diagnostic Procedures

  1. Check and fill coolant surge tank reservoir if engine coolant is low. Pressure test system if necessary. Turn ignition on, engine off. Using scan tool, monitor LOW COOLANT LEVEL. If scan tool displays YES, go to next step. If scan tool displays NO, problem is intermittent. See DIAGNOSTIC AIDS  .
  2. If back-up lights work properly, go to next step. If back-up lights do not work properly, check B/U LP fuse (10-amp). If fuse is open, repair short to ground in back-up light circuit, Pink wire between underhood fuse block and low coolant level switch or Yellow/Black wire between low coolant level switch and PCM.
  3. Remove coolant surge tank. Disconnect low coolant level switch. Connect jumper wire between terminals of low coolant level switch connector. Using scan tool, monitor LOW COOLANT LEVEL. If scan tool displays YES, go to next step. If scan tool displays NO, check low coolant switch connector. If connector is okay, replace low coolant level switch.
  4. Connect test light between battery voltage and Yellow/Black wire in low coolant level switch. Using scan tool, monitor LOW COOLANT LEVEL. If scan tool displays NO, repair open in Pink wire between underhood fuse block and low coolant level switch. If scan tool displays YES, repair open in Yellow/Black wire between low coolant level switch and PCM or faulty PCM.
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