PerformanceTrucks.net Forums - HUGE voltage drop issue....SOLVED?

Well, as some of you know, I have been fighting a voltage drop as I get near ~5000rpm. 13.6 volts down to 9volts. Crazy chit. I could go on for many pages of the things I have tried. I have been through 3 batteries and 3 alternators.

Well I never thought about an amp draw and therefore did an amp draw. There was an amp draw on the battery with key off for like a year and half. After pulling all fuses in the door panel the amp draw was down to .85 amp. YEAH! ALMOST AN AMP!!!! CRAZY!!!! I didn't pull the cigarette or radio fuses under the hood a s had my radio wiring completely disassembled.

There I sat in my truck with every freaking wire I had put in it unhooked on both ends, even the radio, all accessory fuses removed and I still had a freaking amp draw. Sigh. I actually hung my head in defeat. Seriously, hung it. Which as I was hanging it I couldn't help but notice my HPTuner's interface "busy" light was blinking ever so slowly. I was like...hmmmm. I unplugged it and the amp meter went to zero. WOW!!!!

Put truck back together, took it for a drive....works like a charm. Actually shifted when commanded now, obviously...its getting 13.9 volts...not 9 volts. But wtf?!?!!HPTuners interface is causing this?

So I started the process of emailing HPTuners support...(foff :P) Long story short they felt it was something other than the interface. I had (have) to agree, electrically speaking, but I knew the interface was obviously involved in this weird mess, just not sure how it played the role.

I don't know how the pcm works with voltage dump, since the regulator is in my alternator, but I assume if the pcm was told there was too much voltage it could some how protect itself and dump voltage. On a dead battery this would prove to be a very ugly scenario. SO what I want, is a schematic of the OBD II pins. I want to know what happens when a particular pin is grounded.

About a year and half ago I kind of permanently put my interface in the truck. I have never taken it out. I only tune my truck, no need to really. Well, apparently the very last time I put it in a year and half ago I did the following.... LINKY <----clicky

Obviously when the interface is not plugged in the pin doesn't push against the grounded shield. Put the interface in and it pushes the pin against ground. I must know wtf that pin goes to or controls, if it is a hot wire why the F did it not short a fuse out.

Sorry for the long story, I have been battling this FOREVER!!!!:bang: I am actually holding my breath that it is even fixed or gone away yet. LOL Thanks HPTuners for the fast emails!