Wiring Issues

ikeG

ikeG

Oughta Know Better
Apr 19, 2011
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LLY was towed in here for a no start. Had codes P1226, P0302, and a 1094. Wont build rail while cranking but would fuel smoke some out the tailpipe. Pulled a couple glow plugs to find an injector hung open. Customer agreed to start with a set of injectors. Got them in today, fires right up running great. Soon after set a P1223. Injector 1 output circuit. Which the truck came in with same code for cylinder 2..... It is intermittent, it will run like a top then start missing on cyl 1. What is everyones thoughts? Tommorrow going to test circuits for injector 1, ive already confirmed injector 2 circuits were good prior to recommending new injectors. The pins in the bale connector seem fine.....
 
2004LB7

2004LB7

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Dec 15, 2010
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Put a 10 amp fuse in the EDU slot before running it any longer. In case the FICM is going out. You don't want the board to blow a hole in it from an oversized fuse not blowing. Might allow it to be repairable if a capacitor shorts out

I would take the connector off the FICM and prob all the injectors from there. This will test the connection at the injector along with the harness. If you have an LCR meter use that too. Should he around 120 uH for each injector. + Or - about 10 uH seems to be normal but much more then that will throw codes.
 
ikeG

ikeG

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Apr 19, 2011
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Those p1223, etc codes were for the circuit between ficm and ecm based on the diagnostic instructions. But I am going to have to check everything before sending the ficm out.
I just wonder why it switched cylinders after the injector change.

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2004LB7

2004LB7

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Dec 15, 2010
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Ah, ok. I didn't look up the code and just went off what you said. You'll need a scope to see the ECM signals to the FICM. I'd check that before condemning the ECM. Could just be a broken wire or bad connection at one of the pins

But if I remember correctly. The FICM doesn't know when the ECM signal is supposed to be there and will happily run with one or possibly two absent signals without throwing a code. So I think it's more about having a signal out of time. Basically two injectors commanded at the same time or having an overlap. So maybe those two injectors have a shorted wire between them and the FICM is trying to guess which one is correct and which one is a false signal. Would explain the fuel smoke exhaust. Commanding the wrong injector will do that.
 
ikeG

ikeG

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Apr 19, 2011
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I only pulled 3 glow plugs, cyl 8 was the one with thw injector hosing fuel. Cyl 2 had the code set upon arrival. Get it running with new injectors, cyl 1 sets the code now.....

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ikeG

ikeG

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Apr 19, 2011
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It's those stupid round pins in the ecm connector. I've had trouble with those on 4l60 tcm connectors in the past. I should have some saved here somewhere

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ikeG

ikeG

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Apr 19, 2011
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Western PA
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I could get injectors 1, 3 & 8 to shut down and trip their respective P12xx code by wiggling the injector control wires at the back of the ecm connector. So I replaced those 3 female pins as well as cyl 2, since it had that code set when the truck was hauled in. Problem solved.

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