Zip Tie Racing

I have a 2004 f150 STX 4.6L 4x4. The HVAC does nothing when the truck is started or key is on. The dash is blank except it shows that the high beam light and turn signal lights are stuck on. The gear shifter won't unlock out of park no matter what I try. If I plug in an OBD2 scanner it instantly fixes everything. If I unplug it, then it instantly goes back to the way it was. I have just been leaving it plugged in so I can drive the truck. Does anyone have any idea on how to fix this or what the problem is?

HeathMc

Have you tried sticking another battery on it? A bad cell will make things go crazy.

Zip Tie Racing

Yep. I just got a new battery last week

HeathMc

Ok. Let us know what you find. Never heard of this problem before.

Zip Tie Racing

Does anyone have any ideas? I still haven't figured it out

BadFish523

This is a new one to me. Sounds like either a bad computer or bad wiring. Since having a scanner plugged in fixes it have you checked all the wiring around the OBD port?

Mulestang

Could it be the smart junction box? Wait...does it have a SJB or a GEM? I’m no help.

techrep

iTrader: (1)

OBII port shares the same circuit with the cigarette lighter.. look at that too.

Zip Tie Racing

If I unplug the obd2 scanner the cigarette lighter doesn't work also. The fuses are all good

Phil48315

Did you get the battery before or after the problem?

I would pull up a wiring diagram for the OBD2 connector and trace wires for breaks and shorts.