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MDX, 3.2CL & 3.2TL

  1. Disconnect 4-pin harness connector from generator. Turn ignition switch on. Measure voltage by backprobing between PCM 25-pin harness connector terminal No. 20 (Brown/Yellow wire) and PCM 31-pin harness connector terminal No. 5 (White/Red wire). See Figure . See WIRING DIAGRAMS article. If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, go to step  4 .
  2. Turn ignition switch off. Reconnect generator 4-pin harness connector. Start engine and hold engine speed at 3,000 RPM with no load and transmission in park or neutral until radiator fan comes on. Let idle. Measure voltage between PCM 25-pin harness connector terminal No. 20 (Brown/Yellow wire) and PCM 31-pin harness connector terminal No. 5 (White/Red wire). If voltage decreases when headlights and rear defogger are turned on, ALT FR signal is okay. If voltage does not decrease when headlights and rear defogger are turned on, go to next step.
  3. Turn ignition switch off. Disconnect negative battery cable. Disconnect PCM 31-pin harness connector and generator 4-pin harness connector. Connect fused jumper wire between ground and generator 4-pin harness connector terminal No. 4 (White/Red wire). Using DVOM, check for continuity between ground and PCM 31-pin harness connector terminal No. 5 (White/Red wire). If continuity is present, check generator performance. See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. If continuity is not present, repair open in White/Red wire between PCM 31-pin harness connector terminal No. 5 and generator 4-pin harness connector terminal No. 4.
  4. Turn ignition switch off. Disconnect negative battery cable. Disconnect PCM 31-pin harness connector. Check continuity between ground and PCM 31-pin harness connector terminal No. 5 (White/Red wire). See Figure . If continuity is present, repair short in White/Red wire between PCM 31-pin harness connector terminal No. 5 and generator 4-pin harness connector terminal No. 4. 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 symptom or indication goes away, replace original PCM.
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