S2000 L4-2.2L (2004)
12. Check for continuity between body ground and ECM connector terminal C5.
Is there continuity?
YES - Test the alternator.
NO - Repair open in the wire between the ECM (C5) and the alternator.
13. Turn the ignition switch OFF.
14. Disconnect ECM connector C (31P).
15. Check for continuity between body ground and ECM connector terminal C5.
Is there continuity?
YES - Repair short in the wire between the ECM (C5) and the alternator.
NO - Substitute a known-good ECM and recheck. If prescribed voltage is now normal, replace the original ECM.