Problems '08 6.0L K2500HD

[ZigBlazer]

I don't have EFI Live yet, but will soon for my truck. But my dad is having problems with his gasser. I was wondering if EFI live can monitor what the ECM is telling the Alternator to do on his '08 6.0L. And if EFI live can change what the ECM tells it to do.

His is dropping voltage after being under a load to 13v where it should be minimum of 13.9v according to their service bulletin. If the alternator signal wire is disconnected from the ECM the voltage jumps up to 13.7v which must be default, so I know the alternator isn't the problem. It is either a faulty ECM or faulty programming. The truck only has 6,000 miles on it, and is used mainly to plow his driveway, which is when he found the problem.

Thanks for the help

[gmh308]

I don't have EFI Live yet, but will soon for my truck. But my dad is having problems with his gasser. I was wondering if EFI live can monitor what the ECM is telling the Alternator to do on his '08 6.0L. And if EFI live can change what the ECM tells it to do.

His is dropping voltage after being under a load to 13v where it should be minimum of 13.9v according to their service bulletin. If the alternator signal wire is disconnected from the ECM the voltage jumps up to 13.7v which must be default, so I know the alternator isn't the problem. It is either a faulty ECM or faulty programming. The truck only has 6,000 miles on it, and is used mainly to plow his driveway, which is when he found the problem.

Thanks for the help

You can monitor the alternator signal/s but not adjust the alternator operation. Not familiar with this truck but on some models GM uses the BCM to run the alternator via the ECM and the BCM senses the battery current. (G8 operates like this.) If its an 08 it would be under warranty right?

[ZigBlazer]

It is under warranty, but they can't figure it out, and won't replace parts they don't know are bad. So I'm trying to help pinpoint the problem so they can replace the bad part. I think his programming is corrupt.

So Next question, does the EFI Live scan tool allow you to read Generator F-Terminal Duty Cycle (%), Generator L-Terminal Commanded On (True / False), and Generator L-Terminal Duty Cycle (%), or even Requested Voltage? At least then I could try figure out if it is the ECM sending the wrong signals or if the Alternator is not listening.

Another question, can you view if it is in it's Fuel Economy Mode? That is what the dealer keeps telling him it is in. Even though their service bulletin says it is disabled when in Tow/Haul mode and he still has the problem with that on.

[ScarabEpic22]

By Fuel Economy mode do you mean AFM/DOD where 4 cylinders are shut down? If so then yes, you can monitor the proper PIDs and see what DOD/AFM is doing.

Also, is it a NBS or classic truck? 07/08 is the switch point.

The PIDs I see in the Scan tool are the Generator L-Terminal Duty Cycle (%) and Alternator F-Terminal Counts (%).

[ZigBlazer]

I don't believe it shuts down 4 cylinders, but not sure. It is the newer style truck, matches '09s. I don't know all of what fuel economy mode does, but one thing it does is drop the alternator output voltage from 13.9-15.5v to 12.6-13.1v.

That output for L-terminal is what I'm talking about. Thank you.

[ScarabEpic22]

Hmm, doesnt sound like DOD/AFM to me then. Never heard of this fuel economy mode, theres nothing in the ECM other than DOD/AFM AFAIK.

NBS means its uses E38 and T42 controllers. Can you pull the tunes and post them (at least the ECM)? If you could get a log of this happening we have a better chance of tracking it down.

[ZigBlazer]

As soon as I can afford the EFI Live tuner I can save it, but unless the military decides to give me my disability money without another fight I won't be getting EFI until around June. If I could see what the ECM is telling the alternator to do I think I might be able to pinpoint the problem. I don't know if he is going to wait that long, he is the type that if they don't fix it under warranty like they should instead of ignoring the problem, they will be talking to a lawyer soon. I can understand if I had a truck with only 6,000 miles with a problem the dealer won't fix I would be a little pissed too.

[ScarabEpic22]

No problem, Im 3 weeks away from finishing up my jr year in college and Im flat broke so I know what you mean.

Maybe he can have the dealer flash the latest OS in, they can do it under warranty for free. Might do something?