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James, Ford Technician
Category: Ford
Satisfied Customers: 3628
Experience:  Ford Senior Master Tech, Ford gas and diesel expert, ASE Certified
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I have a 2005 F250 with the 6.0 powerstroke. I have recently

Customer Question

I have a 2005 F250 with the 6.0 powerstroke. I have recently had a lot of trouble on cold starts (not necessarily when cold out, but after truck has sat overnight and cranked the first time in the morning, after that first start, i do not have any trouble the rest of the day until the next morning. This happens even when its 70* or hotter outside. I did a OHMS test on my glowplugs at the connectors, all read between 1.2-1.5 OHMS. I think 0.5-2 is acceptable. Then I unplugged the black connector on the GPCM and tested the pink and green wire, and got a 0.00 reading. Which I believe means the GPCM is ok. I took the CAC pipe and boots off to give me a little extra room to get to the GP harness connector,and to clean some oil off. I put everything back, and when I cranked it up, there was a deeper sound on exhaust and no noticeable turbo wine. I went to drive and 0 boost at low rpm and could only bump it up to 5psi. I have a banks 6gun with IQ display, and I received the following codes.P0046:A51VGT solenoid out of range/performance, P0528: FSS Fan speed sensor no signal,P0683:GPCM the two previous P0266 and P0281(2 and 7 injector codes/ had these prior). I dont know if i hit something or knocked a connection loose, but I did not have the code before, and i am not sure what i could have done to cause this. Please help
Submitted: 1 year ago.
Category: Ford
Expert:  James replied 1 year ago.

Hello, unplugging the GPCM shouldn't have affected any of these items. Unless the fan was unplugged or the VGT solenoid. The cold start I would suspect you have a faulty GPCM as they are known to go back and cause a hard start.

Expert:  James replied 1 year ago.

If you aren't building boost and have a deeper noise under the hood. I would suspect the CAC hose has come off the turbo or cooler. That can also cause the P0046 and no turbo boost.

Customer: replied 1 year ago.
Could the GPCM OHMS test read ok but still be bad? Is there another way to tesr other than buying new one and hoping? boots are still on the CAC, and i dont see where it has moved. No cracks in boots either.
Expert:  James replied 1 year ago.

The best way to test the GPCM is to unplug one of the glow plugs and test for 12v here. When you turn the key on it should easily hold battery voltage. If you are only getting 9 or 10v then the glow plugs aren't getting enough voltage to get hot enough.

Customer: replied 1 year ago.
Im going to go pick up a GPCM and we will see if that will take care of it. I will let you know if its a dead end. Thanks
Customer: replied 1 year ago.
Can you point me in right direction with turbo boost issue. I took pipe and boots back off and back on and no resolve. 0 boost. I made aure connector on VGT solenoid wasnt loose...
Customer: replied 1 year ago.
Ok just drove it and just laid on accelerator until it finally kicked in...almost like someone flipped a switch. Could solenoid of been stuck? Should i worry about that?
Expert:  James replied 1 year ago.

The solenoid might have some carbon build up. I remove them and clean the Oliver off the end with some very fine sand paper and this should help.