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MDX, 3.2CL & 3.2TL

  1. Turn ignition off. Disconnect A/C pressure switch connector. Turn ignition on. Measure voltage by backprobing between PCM 32-pin harness connector terminal No. 27 (Blue/Red wire) and PCM 25-pin harness connector terminal No. 20 (Brown/Yellow wire). If around 5 volts (battery voltage on MDX) are present, go to next step. If around 5 volts (battery voltage on MDX) are not present, go to step  3 .
  2. Turn ignition off. Reconnect A/C pressure switch connector. Turn ignition on. Momentarily connect fused jumper wire several times between PCM 32-pin harness connector terminal No. 17 (Red wire) and PCM 25-pin harness connector terminal No. 20 (Brown/Yellow wire). If A/C compressor clutch does not make a clicking noise, go to step  4 . If A/C compressor clutch makes a clicking noise, start engine. Turn blower switch and A/C on. If A/C operates, A/C signal is okay. If A/C does not operate, go to step  5 .
  3. Turn ignition off. Disconnect PCM 32-pin harness connector. Check continuity between ground and PCM 32-pin harness connector terminal No. 27 (Blue/Red wire). If continuity is present, repair short in Blue/Red wire between PCM 32-pin harness connector terminal No. 27 and A/C pressure switch harness connector terminal No. 3. If continuity is not present, Cut temporary key from a non-immobilizer key blank and tape donor vehicle key to it backwards in order to deactivate immobilizer system during testing. Substitute known-good PCM, then recheck. If measured voltage is now as specified, replace original PCM. If measured voltage is not as specified, recheck A/C system. See appropriate AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
  4. Momentarily connect fused jumper wire several times between ground and underhood fuse/relay block 16-pin connector "D" terminal No. 11 (Red wire). If A/C compressor clutch makes a clicking noise, repair open in Red wire between PCM 32-pin harness connector terminal No. 17 and A/C clutch relay. If A/C compressor does not make a clicking noise, problem is with A/C system. See appropriate AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
  5. Measure voltage between PCM 32-pin harness connector terminal No. 27 (Blue/Red wire) and PCM 25-pin harness connector terminal No. 20 (Brown/Yellow wire). If less than one volt is present, Cut temporary key from a non-immobilizer key blank and tape donor vehicle key to it backwards in order to deactivate immobilizer system during testing. Substitute known-good PCM, then recheck. If symptom or indication goes away, replace original PCM. If one volt or more is present, repair open in Blue/Red wire between PCM 32-pin harness connector terminal No. 27 and A/C pressure switch harness connector.
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