I had a sudden alternator failure - no warning lights or beeps, it just stopped working and the battery died. So I replaced it. Now I get a pretty regular beeping, sometimes with the battery light, sometimes without. Worse on short trips, of course. While running (after blipping the RPMs) I get 14.4 volts across the battery, 14.4 from battery positive to chassis. Using Torque app from the OBDII, I'm seeing it move between 12.5-12.8. Engine off, I have 12.5. I Also have 12.4 from the ECU connector to the battery negative. Torgue says 11 volts. This is consistent, doesn't bounce around while driving or wiggling wires.
The battery was nearing it's end anyway, so I replaced that too.
Correct me if I'm wrong, but ISTM the charging system and wiring are fine, but for some reason the ECM has misplaced a couple volts.
I had a problem with the instrument cluster a few months back that required repair. Would the ECM read something from there to report volts? I did check all the connections they were tight (didn't test volts). A note on that: since the repair the tach and speedo will not register for about 20-30 seconds after starting. Seems unrelated.
I suppose I need to drop in a new ECM, they aren't that expensive but I don't want to do that only to find it doesn't help. Was hoping someone here has an idea.