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Air Conditioning Signal Circuit: Insight

  1. Turn ignition off. Disconnect A/C pressure switch 4-pin connector. See A/C SIGNAL COMPONENT LOCATIONS  table. Turn ignition on. Backprobing, measure voltage between PCM connector "A" (32-pin connector) terminal No. 27 (Blue/Black wire) and PCM connector "B" (25-pin connector) terminal No. 20 (Brown/Black wire). See Figure and Figure . If voltage reading is about 5 volts, go to next step. If voltage reading is not about 5 volts, go to step  4.
  2. Turn ignition off. Reconnect A/C pressure switch 4-pin connector. Turn ignition on. Backprobing, momentarily connect a jumper wire between PCM connector "A" (32-pin connector) terminal No. 17 (Red wire) and PCM connector "B" (25-pin connector) terminal No. 20 (Brown/Black wire), several times. See Figure and Figure . If A/C compressor clutch makes a clicking sound, go to next step. If A/C compressor clutch does not make a clicking sound, go to step  5.
  3. Start engine. Turn A/C and blower motor switches on. If A/C operates, A/C signal is okay. If A/C does not operate, go to step  6.
  4. Turn ignition off. Disconnect PCM connector "A" (32-pin connector). Check continuity of Blue/Black wire between body ground and PCM connector "A" (32-pin connector) terminal No. 27. See Figure. If continuity exists, repair short in Blue/Black wire between A/C pressure switch and PCM connectors. See WIRING DIAGRAMS article. If continuity does not exist, substitute a known-good PCM and retest. See SUBSTITUTING POWERTRAIN CONTROL MODULE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INSIGHT article. If symptom or indication goes away, replace original PCM. If symptom or indication does not go away, inspect A/C system. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
  5. Unbolt underhood fuse/relay box. Leave upper cover on fuse/relay box to prevent short circuits and invert fuse/relay box. Backprobing, momentarily connect a jumper wire between ground and underhood fuse/relay box Green connector "D" (16-pin connector) terminal No. 11 (Red wire), several times. See Figure. If A/C compressor clutch makes a clicking sound, repair open in Red wire between A/C clutch relay and PCM connectors. See WIRING DIAGRAMS article. If A/C compressor clutch does not make a clicking sound, inspect A/C system. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
  6. Backprobing, measure voltage between PCM connector "A" (32-pin connector) terminal No. 27 (Blue/Black wire) and PCM connector "B" (25-pin connector) terminal No. 20 (Brown/Black wire). See Figure and Figure . If voltage reading is less than one volt, substitute a known-good PCM and retest. See SUBSTITUTING POWERTRAIN CONTROL MODULE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INSIGHT article. If symptom or indication goes away, replace original PCM. If symptom or indication does not go away, inspect A/C system. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. If voltage reading is not less than one volt, repair open in Blue/Black wire between A/C pressure switch and PCM connectors and/or open between A/C pressure switch and heater control panel. See WIRING DIAGRAMS article.
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