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Discussion Starter #1
Hey everyone. I've had my 2014 F250 CCSB Lariat for a month now and I'm already fixing it ... Not too happy about it, but it is what it is.

I'm doing a big welding job far from home, staying in a local hotel. I drove to the hotel from the pub at night, no problems. Remote-started the truck from the hotel room, could see the lights come on, so I assumed the truck started normally, had my breakfast, and went outside to the truck not running. I tried to start it but the batteries were dead. Boosted the truck, but all the electronics (cluster, nav, etc) shut off when I disconnected the booster cables, with a message saying "Power off to save battery". So I figured, it being -25C (-13F), and the batteries being original, they're pooched.

I replaced both batteries with good new ones. Truck started no problem, but now I had a code and the battery light is on. P0625 - Generator field terminal circuit low. I have dual alternators. Cleared the code, but it came back immediately. Drove the truck 10 mins to site anyway cause I had no other option, everything was fine but the battery light stayed on. No more engine light - went away after sitting overnight.

I checked the Batts with a meter while running, they're 12.8V so obviously the truck isn't charging properly. I was an hour and a bit from home so I just decided to go for it, get as close to home as I could before I had to get it towed. I made it the whole way home, got in the driveway, shut the truck off, now it won't crank again. Batteries aren't dead dead, but it won't crank.

Not sure what to do now. Some guys are saying there's a wire that runs under the motor - I'm about to go check that. My assumption is my primary generator isn't working and the secondary one is just keeping the truck going while it's running, but not charging enough for the truck to start again once I shut it off.

Going to try to find this wire now, but I need the truck on Monday and it's going to be -35C (-31F) out here, so I need the thing to be reliable. Figured I would get a headstart looking for help before I run out of time.

As far as I can tell, there are no fuses for the generators, only a fusible link somewhere near the pass side battery. I've yet to look for it, but will in a moment.

Thanks for any help!

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I would say it's either 1, or both of your alternators if your battery light came back on after new batteries installed.
 
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I would have to agree with what was stated above. I know that you're in a hotel but is there any way that you can plug her in at night?

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Discussion Starter #4 (Edited)
So edit: I don't have dual alternators. I assumed "Extra Heavy Duty Alternator" on the window sticker meant you get an extra alternator ... I.e. additional.

So I have one HD alternator. I back-probed the plug on the alternator and got 12V on the red wire, 2V on the yellow, and 12V on the third wire when the engine is running. Looked black but I couldn't tell.

Does anyone know what values I should be getting on these wires?

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you may still have a bad battery. go have the new batteries load tested and isolate each battery before testing. If they test good, pull the alternator and have it tested.
 

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one of these might have the connector you are measuring and the volts they should be.
 

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Discussion Starter #7
one of these might have the connector you are measuring and the volts they should be.
Larry, that's awesome information. It's exactly what I need, thanks!

Is there any way you could post the remaining diagnostic steps? I'm following them, but I need D14 which isn't posted. If you could post the rest or send them to me directly, that would be amazing.

Engine running I'm getting GENMON = 100% and GENCOM = 56%. When I unplug the generator harness these values don't change. I'm using my Snap-On Ethos Pro to monitor PIDs. Going as far as shorting the two pins at the harness side doesn't change the values either. I would assume that, if the wiring was OK, disconnecting the harness at the alternator would cause GENMON to read 0%, not 100%. So I'm going to guess that the generator is OK and I have a wiring issue ... going to have to pursue that tomorrow.

Would you happen to have a pinout for the PCM so I can check the harness for continuity? I'm going to check the GENMON and GENCOM circuits for a short to ground or B+ but, if I don't see a short, I'm going to assume that I have corrosion somewhere. In which case, I'd like to check resistance from the PCM connector to the generator connector, but I can't find either wire at the PCM connector. A third party source says GENCOM goes to pin 53 and GENMON goes to pin 14, but it appears both of those are empty at the connector so I must be looking at the wrong connector or the wrong pin numbers.

Thanks for the help, this is great!
 

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maybe these will help also...
 

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Wiring diagram.
 

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Remote starting the truck: Your run time will be limited to what you have selected. So it may be 5mins or 30mins max if I recall. After that the truck shuts down on it's own.
 

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Discussion Starter #12 (Edited)
Update: I checked continuity from PCM to generator harness, didn't get anything. Then I went under the truck and cut the zip ties that hold the wires into the loom that run under the crank pulley. Checked again, now I have continuity. Plugged everything back in, started the truck, now I have P0620 - Generator Control Circuit code. The truck still isn't charging.

Might just have to take it in to the dealer and hope for the best. It's cold as hell out here.
 

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That is a code P0620 I think.
 

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last two...
 

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I've always just pulled the cables off the batteries once running to test the alternator. Turn every single electrical thing you can on and pop the cables if it has issues then the alternator is likely bad. I'd say belt but nah the new belts on these are double sided and very grippy though if the belt is on wrong maybe. You should be getting close to 14v though when running so less than 13v is bad.
 

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Discussion Starter #16
Update. I pulled the generator out, had it rebuilt, the truck was fine for 2-3 days, now the battery light randomly comes on and off while driving. Not really sure what to make of this anymore.

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There’s a video some where on you tube that shows a chaffing point for a wire bundle under the passengers side front of the truck. The problem comes from the wires being zipped tied too tight from the factory. You mentioned you cut the zip ties on the harness and gained continuity. Go back and inspect the wires for chaffed areas.
 

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could just overlay a wire.
That harness is a bit of a pain to deal with
 

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Definitely sounds like a broken wire or two in that wire loom. Passenger side, bottom front of the engine, there is a tray that has the wires that go between the batteries and the alternator. Its in there and you cant miss it once you take a closer look with a flashlight and mirror. I had the exact same problem, replaced the alternator AND both batteries and the charge light kept coming on. Charge would fluctuate between 11 and just over 14 which is what it should be. I finally found the wire, insulation cracked and innards corroded right through. I soldered in a replacement section and problem solved, but not before too much money needlessly spent. Charging now starts at low to mid 12VDC at idle, then climbs nicely to 14.2 VDC.
 
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