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Alternator Fr Terminal Signal

  1. Connect system checker harness between ECU and connector. Connect voltmeter positive probe to terminal B14 (White/Red wire) and negative probe to terminal A18 (Black/Red wire). Start engine. Turn headlights on and off.
  2. Voltage should drop and then raise 0-5 volts as headlights are turned on and off. If voltage does not change, stop engine. Check for continuity in Blue wire between alternator and ECU. If there is continuity, check for faulty alternator and/or voltage regulator. If no continuity, check for open circuit in harness.
  3. Test FR terminal diode. Diode is faulty if continuity or no continuity exists in both directions between F and FR terminals of voltage regulator.
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