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Ive gone through several alternators in the last 2 years and since I have an android head unit with forscan Ive been watching stuff lately. I replaced the alternator a couple weeks ago but now my GEM battery voltage fluctuates and is low, as in I’m seeing 11.X volts on occasion. What could be a cause or a place to start looking? Ive sat with a multimeter in the batteries and they’re sitting at 14.X, I’ve got 3/0 power and ground cables, batteries were good last I tested them. I’ll have the alternator tested some evening this week. I also very recently got a ton of new codes that dont go away when deleted. I’d have to double check but I believe they are from the GEM portion of the readings. The codes showed up after i went to start the truck and the dash seemed half lit up.
I didn't realize there was a GEMV PID. Now I'm curious to see if I have it in my list also. The little bit of info described here definitely put the GEM on the list of suspects, but without the codes and some more digging it's still up in the air. From what I've read on the subject the only way to really know if the GEM is your problem it to remove it for inspection and if there are signs of water damage either attempt a repair or replace it.I would suggest going through all your grounds as well, and I mean all of them. There are quite a few, I've found 8-10 so far and I'm sure there's more still. The best batteries and alternator in the world are useless without proper grounding to whatever they supply.
Here is a pic of the codes, figured it would be easier to just post the pics. The GEM is on the backside of the fuse panel under the dash correct? I figured there would be a lot of grounds throughout the truck, looks like ill have a fun time checking all the ones i can find
Yes, the Gem is behind the dash fuse panel. Here is a pretty detailed thread on the diy GEM rebuild. Pop some popcorn, grab a note pad, and a stiff drink, it's a a bit of a read, but loads of good info there. Don't worry if you get a little smoke rolling from your ears, pretty sure it's normal on the first read through. Just your brains cooking, they'll grow back.
How are all your grounds? Especially the cab to frame ground and the battery to cab/frame grounds? If it's the factory battery cables, there is only one each of the battery to frame and battery to cab grounds. They are both off the passenger side battery -ve cable and relatively small. A cable kit I installed recently has some heavy duty grounds going from the alternator and driver side battery going straight to the frame.
udsuth78, thanks that is a great post to use as a guide. While kinda tedious the overall job seems fairly simple. There will be a couple frosty beverages used in the process I’m sure if it comes to that to solve the problem.
The only grounds I know of, atleast that I installed are one going from drivers side battery to the frame, passenger side batter to the engine and a ground strap going from the starter to the frame. Everything else is factory and I haven’t messed with yet.
udsuth78, thanks that is a great post to use as a guide. While kinda tedious the overall job seems fairly simple. There will be a couple frosty beverages used in the process I’m sure if it comes to that to solve the problem.
The only grounds I know of, atleast that I installed are one going from drivers side battery to the frame, passenger side batter to the engine and a ground strap going from the starter to the frame. Everything else is factory and I haven’t messed with yet.
Check the one going from the cab to the frame on the passenger side.
Now that i think of it the ground from cab to passenger frame under the passenger seat is gone. The others i could get to fairly easily i cleaned up tonight. I didn’t have time to take the gem apart to check and clean it all. But i did pull it out and visually inspect the contacts, zero corrosion on any of the terminals and plug ends. Put it all back together and it appears the codes are all still there. It seemed to crank up faster but it could have still been pretty warm from driving it back from the vinyl shop. Hopefully ill have a 2 day break to pull the GEM apart to inspect it properly and clean it all up to be sure. Any other ideas where to look? Could the instrument cluster be a possible culprit of atleast some of the codes since there is a light in the dash for most of them?
Still haven’t had a free chance to take apart the gem to inspect and clean as needed or install the ground strap on the passenger frame rail. But somehow a lot of my codes have cleared themselves. I did end up replacing both battery’s, the part store tester said they were bad but I never confirmed with my usual load tester, either way I have about 400 more CCAs than the old ones
A win for sure but oddly enough after the battery replacement I still had the codes for a while, just checked yesterday for grins and a lot of them were gone. Still have the battery voltage too low code so gotta figure that one out still.
My GEM codes come and go quite a bit. Heck almost half the time Forscan says it can't communicate with it, but if I clear the codes koeo and cycle the key like it says there they are again. The old key in circut fault and 2 for the transfer case shift solenoids.
Oddly enough, or many not odd, I’ve got the same 3 codes. The key code I read is because I removed the piece so it doesn’t ding all the time, can’t remember the conditions to make it ding originally since I’ve had it this way for so long.
Oddly enough, or many not odd, I’ve got the same 3 codes. The key code I read is because I removed the piece so it doesn’t ding all the time, can’t remember the conditions to make it ding originally since I’ve had it this way for so long.
Black wire pink stripe no more incessant dinging. Before I took care of Mr. Black/Pink stripe I was ready to hunt down whomever was responsible for the constant dinging and kick them squarely in the nuts, or ovaries if that be the the case. Possibly repeatedly, yeah would likely have been repeatedly.
