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Coolant Temperature Indicator Test

  1. If vehicle overheats and coolant indicator does not illuminate, turn ignition off. Disconnect 32-pin Powertrain Control Module (PCM) connector C3 (Green). Turn ignition switch to RUN position.
  2. Using a voltmeter, ensure battery voltage is present at PCM connector C3 pin C7 (Pink/Black wire). See Figure -9. If voltage is not present, check wiring. If wiring is okay, replace IPC. See INSTRUMENT PANEL CLUSTER (IPC)  under REMOVAL & INSTALLATION.
  3. If battery voltage is present, turn ignition off and reconnect PCM connector. Connect scan tester at Assembly Line Diagnostic Link (ALDL) connector. Scan engine coolant temperature. If vehicle is not equipped with coolant temperature gauge go to step 5).
  4. Compare temperature of IPC coolant temperature gauge to scan tester coolant temperature while engine is warm and running. If readings differ, go to next step. If readings agree, check PCM connectors and terminals. If connectors and terminals are okay, replace PCM.
  5. Disconnect Coolant Temperature Sensor (CTS) connector. If scan tester indicates -40°F (-40°C), go to next step. If reading is not -40°F (-40°C), check wiring between PCM and CTS. If wiring is okay, replace PCM.
  6. Place jumper wire across CTS connector terminals (harness side). If scan tester indicates 266°F (130°C) or greater, go to next step. If scan tester does not indicate a temperature of 266°F (130°C) or greater, check wiring between PCM and CTS. If wiring is okay, replace PCM.
  7. If TEMP light or coolant temperature Light Emitting Diode (LED) illuminates, check terminal contact of CTS and replace CTS if contact is okay. If TEMP light or LED does not illuminate, check PCM terminal contact and replace PCM if contact is okay.
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