I have a 2006 F350 SCSD 4x4 Diesel, about 70,000 miles.

I've had the P0299 code come on twice now. Both times, the engine light was NOT ON when I shut the truck off. 2-3 days later, go to start the truck, and the light pops on.

I took it to my transmission guy, he's got the same laptop Ford has. This code, and several others (P1812 the 4x4 mode switch, P0620 Generator Control Circuit) also showed up on the laptop, but not on my scanner (he said this is normal the laptop is better). All of them look to have come on at or near the same time. Voltage for P0299 was at 9.6 volts when it came on, engine temp was 80 (cold). I had replaced one battery and was concerned about the other, so he cleared the codes and I got a second new battery.

All went well for about a week, then went for 250 mile drive to river, parked. Next day moved it about 100', still no code. 2 days later, went to start and go home and BAM, there's the damn engine light again and code P0299. Transmission guy said that low voltage at start can sometimes cause the codes, and all had pretty low voltage noted on the laptop when they came on.

Voltage on the truck: What I've noticed over the last 6+ months is that the battery light stays on for several minutes once truck starts, and voltage stays low in the 11's. Then light goes off and you can see voltage jump up to 13+ volts.

Since it looks like the P0299 code came on at engine start, cold engine, for the second time, I'm wondering if this has something to do with the charging system taking so long to 'come on'. I don't remember that battery light coming on like that and staying on for minutes until last August. With 2 new batteries, I've eliminated that as cause.

Truck drives totally normal: Boost, engine and oil temps, voltage (once light goes off stays mid 13 V), power, mileage, etc.

Any clues or thoughts before I try to get it to a shop?

 

That's a turbo underboost code. Check ALL your turbo plumbing for leaks, check the MAP sensor hose and EBP tube, and clean y our turbo.

 

With exception of cleaning the turbo, all else looks ok. Question though, how can a 'turbo underboost' code come on right at startup, dead cold engine, wouldn't that be something to come on when driving?

 

Sounds like you have a weak battery, the charging system will stay around 12vdc until the glow plugs shut off, the wait to start lamp has no bearing on how long the are on, it is just a reminder to let them warm up before cranking. I could see how low voltages could cause codes if the PCM doesn't see proper response via the sensor. So I would agree with him. I don't recall my battery light staying on for several minutes after starting. I would get the batteries checked out and replaced under their respective warranties if needed. I think you are on to something.

 

Have the alternator (s) checked too.....

 

Batts are both brand new, one last week, one a couple months back.

 

I do, unfortunately, have dual alternators. However, once the battery light goes off, you can actually feel/hear when it starts charging (sound/feel - know what I mean? Not smoking anything funny here). From then on it's always in the 13's, typically around 13.6 v.

That said, if that's charging properly, aren't they fine? OR, could one be having an issue and the other making up for it? Can you test them individually while in the vehicle, or do they both have to be removed?