S2000 L4-2.2L (2004)
Alternator: Testing and Inspection
Alternator FR Signal Circuit Troubleshooting
1. Disconnect the alternator 4P connector.
2. Turn the ignition switch ON (II).
3. Measure voltage between ECM connector terminals B20 and C5.
Is there about 5 V?
YES - Go to step 4.
NO - Go to step 13.
4. Turn the ignition switch OFF.
5. Reconnect the alternator 4P connector.
6. Start the engine. Hold the engine at 3,000 rpm with no load (in neutral) until the radiator fan comes on, then let it idle.
7. Measure voltage between ECM connector terminals B20 and C5.
Does the voltage decrease when the headlights and rear window defogger are turned on?
YES - The alternator FR signal is OK.
NO - Go to step 8.
8. Turn the ignition switch OFF.
9. Disconnect ECM connector C (31P).
10. Disconnect the alternator 4P connector.
11. Connect alternator 4P connector terminal No. 4 to body ground with a jumper wire.