Alternator FR Signal Circuit Troubleshooting

This signal informs the ECU when the alternator is charging.
1. Connect system checker harness between ECU and wire harness connector. Disconnect ``B'' connector from main wire harness only, not the ECU.
2. Turn ignition switch to On position and measure voltage between terminals B14 (+) and A18 (-) of system checker harness. Approximately 5 volts should be present. If 5 volts is present, proceed to next step. If 5 volts is not present, substitute a good ECU and recheck voltage. If voltage is now as specified, replace ECU.
3. Turn ignition switch Off and reconnect ``B'' connector to main wire harness.
4. Start engine and allow to reach normal operating temperature, turn on headlights and rear window defogger and check voltage between terminals B14 (+) and A18 (-). If voltage decreases, alternator FR signal is OK. If voltage does not decrease, stop engine and proceed to next step.
5. Disconnect ``B'' connector from ECU only. Do not disconnect from main wire harness.
6. Disconnect battery ground cable and check for continuity between terminal B14 and suitable body ground. If continuity exists, proceed to next step. If continuity does not exist, proceed as follows:
a. Disconnect green connector from alternator, then connect white/red wire to body ground and check for continuity between terminal B14 and body ground.
b. If continuity exists, check alternator. If continuity does not exist, repair open in white/red wire between ECU and alternator.
7. If continuity exists in step 6, proceed as follows:
a. Disconnect green connector from alternator and check for continuity between terminal B14 and body ground.
b. If continuity does not exist, check alternator. If continuity exists, repair short in white/red wire between ECU and alternator.