Not sure if you read my first post, but here it is. 04 F150 XLT 5.4L 2 WD My batt. light came on when I was going to work. I drove with the light on to get a new battery hoping that was it, it wasn't. I got home and put the multimeter across the battery, it read 12.1v. So I ordered, and then replaced the alternator. I put the multimeter on it, and it's charging 14.6v. BUT the batt. light is still on!! Using my Diablo tuner diagnostics, it showed a P0622- general field terminal circuit and a P1000- OBD systems readiness test not complete. I checked the wires and all are good. I tested the wires all the way to the box mounted on the firewall and the fusible link is fine. Everything is working, so I don't think it's a fuse. Is it possible my computer got toasted since the alt. quit charging and I kept driving it? (prob. around 19 mi. with it on) Thanks

 

Not sure but my buddy's F-150 had a battery problem. Turned out the terminals needed to be cleaned and once that was done the light went away and everything was fine. Good luck.

 

This is weird. The light doesn't come on right away, it takes around 1 1/2 - 2 minutes before it comes on. Does anyone have an electrical schematic I can see? Or is there a Chiltons manual out for these yet? I drive way too far, too often, to be unsure of my truck.

 

Check your PM.

 

Lemme think about that for a bit. I'll get back to you soon.

 

I'm at a loss here. I don't know where the 2 light green wires go after the elec box on the pass. side firewall. This may be nothing, but I do hear a faint, high pitched whine when the radio and heater are off with the engine running. Your help is much appreciated. Thanks

 

bump

 

OK, so I got a Haynes repair manual, and it didn't tell me anything I didn't already know. The wiring diagram ended when the light green wires got to the elec box on the firewall. The code P0622 aternator field terminal circuit failure has no description or what to look for. There is no code P1000 in the book, which is the OBD sytem readiness check not complete. WTF!!!! The light doesn't come on until the engines been running for at least 1 1/2 minutes, and now I'm noticing the in gear idle speed is up to 850-900 RPM. And there is a high pitched whine in the cab with no radio or heater turned on. All my accessories work, so there's no blown fuses. Anyone got a clue????????????????? I don't want to take it to the dealership since they botched up a sparkplug change, and I have no faith in them whatsoever!

 

Maybe try pulling the negative on your battery for about 5 minutes and try it again? Might clear itself.

 

The batt. was disconnected for 4 hrs before I replaced the alt., but I'll give it a shot. (fingers crossed)

 

I dont know if this will help but here are some troubleshoting pic that I took out of my factory manual. It mentions a fuseable link but does not show it.

 

Here are some more.

 

This is what I needed!!! THANK YOU VERY MUCH!!!!!!!!! I hope I can find it now, I'll keep you posted. YOU DA MAN!!!!!!!!!!!!!!!!!!!!

 

You know what's kinda funny? There's no test for the light on with the engine running, and charging between 13-14.6 volts. Which is EXACTLY what mine's doing. Although I was reading in another thread that there are a few different regulators used in the alts. for our trucks. Maybe the one I replaced mine with is the wrong regulator? Autozone DL3622-16-10 Dura

 

I must of read your post wrong I thought it said it was not changing. Here are some more pics from the manual. These tests look a little harder to do if you dont have a scann tool.







Sorry about the lighting its hard to take pics with a flash off.