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Alternator Fr Signal: MDX

  1. Start engine and allow to idle. With the Honda PGM-FI Tester or the HDS monitor the ALTERNATOR in the DATA LIST. If the indicated percentage is varied when the lighting switch is turned on, the alternator signal circuit is OK. If the indicated percentage is not varied when the lighting switch is turned on, go to next step.
  2. Turn lighting switch and ignition off. Disconnect alternator 4-pin connector. Turn ignition on. Measure voltage between ground and alternator 4-pin connector terminal No. 4 (White/Red wire). If about 5 volts is present, replace alternator, then go to step  1 . If about 5 volts is not present, go to next step.
  3. Turn ignition off. Disconnect PCM harness connector "A". See Figure . Check for continuity between ground and alternator 4-pin connector terminal No. 4 (White/Red wire). If there is continuity, repair short in wire between alternator 4-pin connector terminal No. 4 (White/Red wire) and PCM. If there is no continuity, go to next step.
  4. Check for continuity between PCM harness connector terminal A25 and alternator 4-pin connector terminal No. 4 (White/Red wire). If there is continuity, update the PCM if it does not have the latest software. Substitute known-good PCM, then recheck. If symptom or indication goes away, replace original PCM. If there is no continuity, repair open in wire between alternator 4-pin connector terminal No. 4 (White/Red wire) and PCM.
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