Not running right. U1800 P0090 - Chevy and GMC Duramax Diesel Forum
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post #1 of 4 (permalink) Old 01-22-2020, 08:05 AM Thread Starter
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Join Date: Jan 2020
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Not running right. U1800 P0090

Hey all. I've read many things from this forum before but finally decided to join as I couldn't find a post with quite the same problem and I'm getting stumped. Truck is a 2003 LB7 I brought back from texas with me a few years ago, shes got about 260k on her right now. Anyway I was out with it the other night hauling some snow blowers around and helping my uncle with some accounts in good ol Wisconsin. Stopped for breakfast after about 9 hours of the truck running and was inside for maybe 1 hour. When I started back up it gave me the range shift inhibited which Its done before but always gone away. Anyway when I shifted the "range shift inhibited" on the dash went away and truck all seemed normal and was functioning good until I went to make the drive home 5 hours after that, then she wouldn't come past 3rd the whole time. Tried shutting it off with the key trick even unhooked the batteries and it still wouldn't go away. Now here's the fun part (I know this is getting long but bear with me please!&#x1f605 so I limp her back to my house and park in the garage to diagnose. Thinking it's my nsbu switch, ok order that. While I'm waiting for that to get here I decide to do my oil change and change my fuel filter with the new CAT filter adapter I bought. First start up after is fine. Truck runs about 10-15 mins then I shut her down and go to bed for the night. Next morning go to start her to leave, fires up totally normal minus being a little cold and then dies like a shut the key off not even a minute later. So trying to troubleshoot. Can not get a consistent result out of this thing. Rebuilt the fuel filter head with no luck. Can prime it and prime it bulb takes forever to get hard but will get hard, sometimes she starts sometimes she doesnt. Its run for as long as 15 minutes on high idle and still just killed itself. My buddy gave me a good FICM he had and I plugged that in. Oddly it makes the truck start easier and a little more consistent but it still dies intermittently? I've heard so many different possibilities im just wondering if anyone has any other ideas? Going to check all the grounds today, as well as the harness around the alternator to look for damaged wires. My buddy with the FICM told me to look at the ignition switch as well. Is there a fuse that could possibly contribute to any of this? Could the CAT filter and adapter possibly be the cause? Would seem weird to me if they are but its the only thing I've done since I parked her. Has anyone heard of an nsbu switch causing a freak out like that? Also saw a couple posts that mentioned injectors 😐 fingers crossed that's not it. Anyway thanks in advance to any help, sorry for all the reading Haha.
Oh, truck has EFI live as well if that matters

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post #2 of 4 (permalink) Old 01-23-2020, 08:44 AM
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Location: Maurice, LA
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I don't have any ideas about your main problem but can tell you that the CAT filter is NOT a good idea unless you ave a Lift ump that incorporates a water separator.

Water in your diesel can ruin a diesel engine in short order.

2008 Silverado 2500HD CCSB LTZ Diesel
FASS 95 Lift Pump (with Baldwin filters), Edge Insight CTS Monitor on a Windshield Mount, Nicktane Fuel Filter Adapter w/ CAT 306-9199 UHE tertiary fuel filter, Bilstein 5100 Stock Height, Bushwacker Bed Rail Caps, AMP Research Bedstep, Fumoto oil drain valve, Dorman PS Oil cooler, Pioneer AVIC 7200NEX GPS/Stereo, Air Lift LoadLifter 5000 Air Bags.
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post #3 of 4 (permalink) Old 01-23-2020, 10:28 AM
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see pm

Ron Nielson
2008 Silverado LT, CCLB, Edge Insight CTS
2009 Arctic Fox 29-5T, Silver Fox Edition, Onan 3600 LPG generator
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post #4 of 4 (permalink) Old 01-24-2020, 09:59 AM Thread Starter
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Update on truck. Tested with buddys FICM. Seems to start easier but has the same shut off problem. Returned fuel filter to stock and rebuilt filter head. Cleaned all ground points and battery connections. Installed new ignition switch. Truck is still doing the same thing. Shuts off like I'm turning the key it doesnt sound like its starving for fuel or bogging down or anything. I'm very confused at this point haha. Could it maybe be a pinhole leak in the fuel system? Some electrical gremlins somewhere?
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