That's what I don't get, I have done the big 3 already, and have tried two different new alternators, and now a new battery as well.

Already tried the new battery, no change.

 

What size alternator are you running 145a?

 

Yes sir.

Like I said before, I was not having this problem before the blower. The ONLY things that changed was the blower, engine harness, and fans. Same alt (well, now a new one), same battery, same big 3, same stereo crap, same everything. Points to three possibilities - blower (which....wtf? Not possible), engine harness, or fans. I've tested everything else out and it's not any of them. I don't think it's the fans because they shut off over 45mph. That leaves just the engine harness, which is why I'm now looking into whether or not I got all the grounds hooked up.

 

engine harness? I didn't follow that swap, but you have the same truck as me and even though my problem was solved by fixing my HPTuner cable, which isn't your issue, I would chase out that engine harness cable.





That was the pin on my harness that was fubar'ed.





Pin/Circuit #/Name
1 -- -- Not Used

2 PPL 1132 DLC Class 2 Serial Data

3 -- -- Not Used

4 BLK 1850 Ground

5 BLK/WHT 451 Ground

6-15 -- -- Not Used

16 ORN 640 Battery Positive Voltage

https://www.performancetrucks.net/fo...9&d=1238545096

https://www.performancetrucks.net/fo...0&d=1238545096

I know this won't be your area of problem, the OBDII port, but you need to ensure the wires that are in the circuitry that I was grounding out at the pin isn't fubar'ed when you did the engine harness swap in some way. Any of them pinched? so on and so on....

Find out which pin on the pcm harness is that pin in the OBDII port that I was grounding, pull PCM and check that pin to ground for continuity. I never figured out what that pin really did but the ground on the back of the motor is in the circuitry for it.

 

Yea, just noticed post 26, not sure how I missed that before...

Could it be something with the tune?

 

Have you double checked every ground? Also, check the ground wires going into the connector, seen those go bad before. I had the same issue and found the bolt going to my ground on the engine block had become slightly loose.

I know it doesn't seem possible but getting 2 bad voltage regulators is a possibility.

 

Wondering if you've come up with anything for this?

 

curious on this also now, my company truck is now dropping almost off the gauge above 4200ish.brand new battery,belt, tensioner,and alt 100% stock with 260k miles.

 

This is just an aside...hit those(any ones you expose)pins with a good electronics contact cleaner...not the kind with lubricant in it. The pins can lose the great low-resistance they have when new due to contaminants...even from short contact with the air.

I've seen many problems go away after cleaning connector pins and circuit card edges. These were ones that occured in much cleaner environments than a vehicle operates in.

 

I still haven't checked my grounds, but I will do that as soon as I get a chance, and clean the PCM connectors. Verified today that it is indeed an RPM only issue, not a throttle position issue. Even at light throttle above 4200-4500ish it drops to about 11.8-12v.