My tuner got this code reading while tuning my car yesterday. It doesn't flash the SES light, but HP Tuners references it as "Generator L Terminal P1637". It has something to do with the alternator right? Because it takes about 10 minutes of driving or idling for the car to come to a solid volts reading. From startup until about that 10 minute mark, the Volts meter is bouncing violently from 11-15 volts. Help?

im no genious and i know its not a vette. here is a good read on it. sorry i come up with this. i love studying things such as this

http://forums.corvetteforum.com/c5-t...l-circuit.html

Do you know what any of that means?

I just read the post, and it was jiberish to me

Also, when those guys were talking about having a bad ground, and that was why they had the code...do you think that would be my issue, considering that my volts reading stays constant after the car warms up? It seems as though if the grounds were the problem, the issue wouldn't disappear just because it was at operating temp?

Are you using a Fbody or truck/vette alt?

Fbodys use the single wire style and truck/vettes use a two wire style

Fbody single wire type.

ok here. damn it i hope one of these helps.
http://www.gearchatter.com/viewtopic8959.php

http://www.ls1tech.com/forums/pcm-di...ode-p1637.html

I'd venture to say you're getting that code because of the funky alt output on startup. I had a low charge issue until I made sure the alt case was grounded correctly. (The carshop acc brackets were anodized so they didn't conduct very well). Make sure grounds are solid (loosen, make sure it's metal to metal and not metal to paint to metal) and try it again?

I had the alternator checked at Advance today, everything seemed good excelt they said the battery could use some charging, which wouldn't have anything to do with my situation.

I guess I'm gonna have to buy a new connector for the atl and see if that fixes it.

What a boner shrinker. The thing left me stranded, I'm 20 miles from home waiting for a flat bed as I am typing this out. I tried fixing a bad ground and had no luck, can't really do much until the connector and wire I bought come in the mail, and hopefully that fixes the problem. If not, I'm not entirely convinced the alternator is shot, due to it passing a charge test at Advance, so I don't know what it could be...son of a biscuit...

Did you make a splice from the ECU to this wire going to the alternator? If so i would check the integrity of this circuit at your splice point

Also it could end up being a bad ECU, hopefully not but if the alt is really ok there isn't too much left to this circuit.

You will drain your battery pretty fast without the alt running, especially as it hasn't been working correctly. also the more times you drain a lead acid battery the worse it gets pretty quick as the battery construction of a lead acid battery is not good for deep cycling

There aren't any splices that I know of, pocket could answer that question better than I can though. Wouldn't HP Tuners show signs of a bad computer while you are tuning? Literally theonly thing wrong with the car is this alternator problem.

the ecu's cpu and memory can be functional but the driver for the alt may not. i am not sure what the connection is inside the ecu for this circuit but it is probably a bipolar transistor or mosfet driver, if this is failed it could result in this as well. if you had a spare ecu to swap in/out this would be an easy way to eliminate that concern, but if not i would try everything else first

His alt connector is a single wire directly from the PCM. I did have to lengthen it for his swap

According to my tuner, a PCM is either good or bad. If you've got a reading from your PCM, its fine

A simple test would be to check for voltage on the connector terminal with the IGN on. The PCM knocks the voltage down some, so it wont be 12v

The ECU is actually a multi-functional module that consists of a large array of different functions including the core processor, memory, communication ports, discrete i/o, analog input/output functions, etc. You can have a failure on an individual i/o circuit and still have the rest of the module functional including the ability to program it.

I don't have a schematic of this ECU but failure on the device being driven can lead to failure of the driver in the ecu if it does not have proper short circuit protection to limit its current, etc. Since this is the most expensive part it is also the last one to swap.

Fortunately in this case it is overall a simple circuit and the component search method of troubleshooting by swapping parts and checking the circuit should get it resolved.

Also you may want to make sure the battery you are using is in good health as a lead acid battery that is going bad can drag down the alternator.

Ya I was told it is 5v. I bought a new connector for the alt side of the wire, when it gets here and I try it, if I find that it isn't fixed my next step will probably be a new alternator.

If the PCM terminal is bad you can wire the alt like a carb swap and it still function

http://www.ls1tech.com/forums/conver...aq-thread.html

If this connector I bought doesn't fix it, and a new alt doesn't work, I will return the new alt and do that wire rig job and be done with it.

Nick..just to add my .02, since Im living vicariously through all you guys that are working on your cars while mine is covered up...

I had issues with charging at first. I replaced the alternator, and re-pinned the plug on the alt. The wire that goes to the Alt plug is VERY tiny. Its very prone to breaking down near the pigtail.

So I ordered the new pigtail. It should come with 5 white wires. You can de-pin the 4 that you dont need, and keep them for spares, since they already have the correct ends.

When you splice that in, only trim the harness you bought about an inch or so. Trace the red wire up as far as you can, even if you have to cut open your harness to get to it. Solder it, and maybe leave that area alittle easier to get to, if you ever have to do it again. Thats why I said trim an inch from the new wire, in case you have to add another wire in the future, you will still be able to reach.

When I did that, my charging issues went completely away. Between that, and the extra ground straps, I get awesome charging, and nothing flickers when going WOT or when idling, which was also an issue I had.