High ECM voltage?

[Rhet]

So a couple of weeks ago I got an ultragauge, since then every time I start the car I have gotten a high ECM voltage warning alarm, usually between 14.95v and 15.05v, just one time then it goes away. I had just assumed it was some anomaly when starting up. This morning when I was driving around the alarm kept going off every couple of seconds anywhere from 15-15.5v. I added ECM voltage to my gauges and kept an eye on it, it was bouncing around a lot, anywhere from 14.9-15.6v but mostly holding around 15.3v. This evening when I was out and about it was doing the same thing but staying mostly between 15.1-15.2v. No trouble codes and no other symptoms that I've noticed.

I have only a basic knowledge of electrical stuff, but I'm thinking maybe a short or bad ground somewhere? Where should I start to try and diagnose this?

I'm totally stock fwiw [for now, these forums are going to do bad things to my bank account ]

 

[rodslinger]

With so many things being controlled via CAN system instead of regular old analog voltage it could be some strange and erratic data exchange between the ultragauge and your car.

I would simply unplug the ultragauge and check battery voltage when the car is running. Re-connect the ultragauge and see if the battery voltage stays the same or goes up. Help rule out the issue being one item or the other. Either the ultragauge is misreading the voltage it or it is actually causing an issue creating an overcharge from the alternator.

 

[Rhet]

Tried with the ultraguage plugged in first, was 15.05v. Unplugged was 15.2v. Plugged it back in got 15.08v. Also noteworthy, the voltage on my multi-meter was actually very stable vs the ultraguage, with the ultragauge bouncing around a lot.

Decided to go get lunch after testing that, after driving about 10 minutes the voltage rather suddenly dropped to around 13.9 before popping back up and staying between 14.15-14.25v. Now I'm just confused...

 

[ShawnB]

I have a digital voltage gauge hooked up in my car. Runs 15.2 volts first 10-15mins. Then drops to 14.0-14.9v. I believe our alternator does a very hard fast charge on our small battery, then drops to what is considered normal.

I never see the voltage drop under 13.6volts while engine is running.

Sent from my VS980 4G using Tapatalk

 

[Rhet]

Hmm, yesterday morning I was driving around for ~40 minutes and it never dropped back to 'normal,' last night I was only driving for about 20 minutes. I'll definitely be keeping an eye on it with that in mind though.

 

[ShawnB]

Sometimes i worry, because a battery can explode with that much voltage for a long period of time.

Sent from my VS980 4G using Tapatalk

 

[rodslinger]

Well now you guys had me curious.

I went out and checked the car. Battery voltage was at 12.6v before starting which is about where I would expect it.

Immediately after starting it kept itself between about 14.6 and 14.75. I drove it around the block, turned lights on and off, A/C on and off, radio, etc... It pretty well held between 14.6 and 14.75vdc.

Mine is a 2013, 1.4 with auto. Only mod is a tune. No gauges connected, aftermarket radio or other bits.

 

[Fry]

I had some voltage issues last year. Most of the time, a bit of high voltage is caused by the colder temperatures. It's normal winter behavior.

Now, if ...things... start happening electrically, then it's not normal. My issue was the radio restarting and headlights dimming. My ultraguage picked up voltages in excess of 16 volts at the times when those things happened. After traveling to two dealerships, it turned out to be a disconnected ground wire that was prohibiting the battery from properly charging. Thus, the alternator had to work extremely hard to try to compensate. This caused various electrical devices to shut off to protect themselves from that high voltage.

 

[ben416]

I had some voltage issues last year. Most of the time, a bit of high voltage is caused by the colder temperatures. It's normal winter behavior.

Now, if ...things... start happening electrically, then it's not normal. My issue was the radio restarting and headlights dimming. My ultraguage picked up voltages in excess of 16 volts at the times when those things happened. After traveling to two dealerships, it turned out to be a disconnected ground wire that was prohibiting the battery from properly charging. Thus, the alternator had to work extremely hard to try to compensate. This caused various electrical devices to shut off to protect themselves from that high voltage.

I have had the headlight flicking problem at times too recently. Dealer can't find the issue, but thus far, my voltages haven't gone above 15.5 in a while. I have the UltraGauge set for an alarm at that level. It was jumping around though, and I have had odd behavior from my dash cam. Anywhere between 14.2-15.4 with the RPMs steady. I will have to ask the dealer to look for loose ground cables. Do you have any idea where your loose cable was?

 

[Fry]

I have had the headlight flicking problem at times too recently. Dealer can't find the issue, but thus far, my voltages haven't gone above 15.5 in a while. I have the UltraGauge set for an alarm at that level. It was jumping around though, and I have had odd behavior from my dash cam. Anywhere between 14.2-15.4 with the RPMs steady. I will have to ask the dealer to look for loose ground cables. Do you have any idea where your loose cable was?

I didn't see it myself, but the dealer told me it was underneath the battery.

 

[ben416]

I didn't see it myself, but the dealer told me it was underneath the battery.

Thanks! I'll mention it to them next time I'm in for service.