2012 CRV. My alternator died and the charging system MIL never illuminated. In fact there were no DTCs stored in the ECU for low voltage or alternator failure. The charging MIL itself is working fine as it illuminates for a few seconds when the key is turned on. Any advice what to check is appreciated. I don't want to get stuck again in the middle of nowhere with a dead battery because the warning system doesn't work. I suppose it could be a bad ECU but there is no indication that it is bad as everything else seems to be working. Thanks

 

Gotta think a little more old-school, and forget that the DTC ever existed, because more than likely an engine module wasn't made for the alternator, and simply clearing the DTC doesn't fix the battery or alternator (obviously.. ;-)) if there was a problem. Honda likes to keep it rather simple. This is why there is no Module for the headlights or other unnecessary things like in other manufacturers that solely depend upon CAN-BUS modules.

If your battery is more than 5 years old, you just change it, that's as about as long as these 400CCA to 550CCA batteries last in hot/cold climates. Also, have your mechanic check the actual "health" of the alternator. If the battery is newer, chances are you won't see any issues. If you see dimming lights or the instrument panel start to light up like an XMAS tree while driving, you'll know that's the alternator.

Sometimes, module warnings aren't going to help. On the 2012 CRV you should be about 12-15 volts on the alternator.

 

There is a reflash available for poor charging strategies. Its old, but might be applicable to your situation.

Naw, this is beyond old school.

In addition to the expected ELD(which is super old school), this charging system also utilizes a current sensor and the alternator is PCM controlled via LIN bus communication. If working properly there should be low voltage codes in most, if not all, of the modules.

The basics should still be checked(like battery condition and all connections) of course,but there could be more than just the basics at fault.....

 

Well yes, the dashboard lights going crazy was my first indication something was very wrong. Next the car had no power - pretty much had to floor it to just crawl. The issue is that by that time the battery was almost drained. I was able to go about another 2 miles from when the dash light show started. Point is the alternator must have died well before then. The battery had enough juice to last for a while but once the dash goes crazy its just about game over. Had the charging MIL lit up when it was supposed to I could have made better decisions to get home quicker instead of getting stuck and getting towed.

I guess there is nothing obvious to check like a fuse or something that might cause this.

 

The basics check out fine... battery is good and all connections tight. I would have expected to see DTC P0562 - charging system low voltage or even P16BB - alternator B terminal circuit low voltage. But there were no codes stored. Hence the PCM would have no reason to turn on the charging MIL if it didn't see any relevant DTCs.

Willing to try a reflash for the charging methods but not sure how to go about finding a tech that could do it. I don't have that kind of gear.

I suppose I could try to recreate the situation by loosening the B terminal connector momentarily and see if the codes are stored and the MIL lights up. It's a rebuilt alternator with a lifetime warranty but nothing lasts forever. It's not a comforting feeling driving with a faulty warning circuit.

 

This might be the answer I found googling....

It could be the diode pack in the alternator, they are designed so current only flows from the alternator to the battery, when they fail they allow the current to flow back and the battery doesn't get charged, but because the alternator is still outputting current the light doesn't come on. Could also be the VR, allowing enough voltage so that the light doesn't come on, but not enough to charge the battery especially if you are running lights/heater/wipers, etc.

The second one seems plausible in my case I was measuring 11.5V loaded and I read articles where it says the DTC wont be set until it get down to 10V.

Oh well, guess the system isn't foolproof.