Duramax Diesels Forum Truck of the Week
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Old 07-24-2015, 06:55 AM
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Default #1 injector shorted

Hello all, I've spent a lot of time looking up other threads to find my answer and haven't so here we go.. I'm getting ficm codes p0201,p0204, p0206,p0207, p1261, at first I thought it was the ficm itself, but after getting about 5 different opinions(ficm, ecm, 4 bad injectors, chafed wires in the ficm wiring harness, or ecm harness), my last option was the take it to the dealer for a definate answer, they came to the conclusion that #1 injector had shorted to ground causing the ficm to also shut down injectors 4,6,7. They said I obviously need #1 injector replaced, along with the two injector harnesses for the passenger side as well as the whole ficm wiring harness. The thing is I've gone through the ficm harness end to end and can not find any cuts or chafes or anything that looks bad, I'm going to change the injector but how can I be sure it wont just short out again? Also I can't seem to find new injector harnesses anywhere online nor can I find a thread on here with anyone saying they've had injector harness problems, lly truck seem to have injector harness issues like crazy but can't find anyone with an lb7 with injector harness that went bad, so if anyone can shed some light on why my injector shores would be great.
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Old 07-24-2015, 06:59 AM
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If you need an lb7 injector harness let me know. I've got an entire engine wiring harness from an 01 lb7..


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Old 07-24-2015, 07:05 AM
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Quote:
Originally Posted by clrussell View Post
If you need an lb7 injector harness let me know. I've got an entire engine wiring harness from an 01 lb7..


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Thanks a lot ill keep that in mind, what I'm really trying to figure out is if I even really need them, or if I should just swap out the injector and hope it doesn't short again
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Old 07-24-2015, 07:06 AM
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Quote:
Originally Posted by RPierson51 View Post
Thanks a lot ill keep that in mind, what I'm really trying to figure out is if I even really need them, or if I should just swap out the injector and hope it doesn't short again

I've never seen one short. But I'm not going to say it's not possible.. Have you been in the valve cover yet? You might find your problem


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Old 07-24-2015, 07:18 AM
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After work toady a plan to open it up and take a look, I was going to wait till I got the injector harnesses so I could open the valve cover, change the injector and harnesses and put it back together in one day as the truck doesn't fit in my garage and didn't want to leave it outside apart, but I guess I wont know what's up till have a look, probably today
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Old 07-24-2015, 07:23 AM
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Quote:
Originally Posted by RPierson51 View Post
After work toady a plan to open it up and take a look, I was going to wait till I got the injector harnesses so I could open the valve cover, change the injector and harnesses and put it back together in one day as the truck doesn't fit in my garage and didn't want to leave it outside apart, but I guess I wont know what's up till have a look, probably today

I'd be happy to send you a harness and if you don't need it send it back. Can take one to the post office today and send it via priority.


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Old 07-24-2015, 07:31 AM
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All you need to do to verify is get out your multimeter and remove the harness from the number 1 and 3 injectors. Then check the resistance (ohms) of each one if injector 1 is shorted it will read a very low number. Before taking it apart just take a mesurent at the connector coming out of the valve cover for the 1 and 3 injectors totoake sure it even needs to be taken apart.
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Old 07-24-2015, 07:33 AM
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All you need to do to verify is get out your multimeter and remove the harness from the number 1 and 3 injectors. Then check the resistance (ohms) of each one if injector 1 is shorted it will read a much lower number. Before taking it apart just take a mesurent at the connector coming out of the valve cover for the 1 and 3 injectors totoake sure it even needs to be taken apart.
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Old 07-24-2015, 08:51 AM
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Quote:
Originally Posted by bmc1025 View Post
All you need to do to verify is get out your multimeter and remove the harness from the number 1 and 3 injectors. Then check the resistance (ohms) of each one if injector 1 is shorted it will read a very low number. Before taking it apart just take a mesurent at the connector coming out of the valve cover for the 1 and 3 injectors totoake sure it even needs to be taken apart.
^ This

Before digging into your motor, you should verify the dealer's findings. I have found that dealers can be (not always the case) massively incompetent.
Quote:
Originally Posted by RPierson51
They said I obviously need #1 injector replaced, along with the two injector harnesses for the passenger side as well as the whole ficm wiring harness.
(Emphasis added)

The fact that they're telling you to replace so many components indicates that they didn't bother to track down the root cause and are just throwing parts at it hoping it will fix the problem. If they knew for sure, they'd be able to tell you "replace injector 1" or "replace the injector harness for injectors 1 and 3".

You can check the connection to the injectors using the method stated above. If you have a access to a wiring schematic, you can check the wires between the FICM and injector harnesses as well.

Remove the connector from the FICM and probe wires based on the description in the schematic. You trace wires on the schematic (for example - making this up completely - pin A3 on the FICM connector may go to injector 7 ground) and measure resistance across the two ends. You want to look for any opens (typically megaohm range or above) as well as any low-to-zero ohm connections. Also probe from one of the pins to ground to check for bare wires touching the engine. This is where you need to verify all connections with the schematic. You want to ensure that the pin you are probing does not intentionally connect to ground somewhere along the path.

If everything passes here, the problem is not harness related. You should also have found that all of the injectors are in a similar resistance range. This won't rule out an injector as being the culprit, but you'll have verified that the harnesses aren't at fault. The next check I'd do is the harness between the bail connectors and the FICM. Same process here.

Finally, remove and inspect the connectors. Look for any signs of corrosion and for bent or broken pins. Issues with the bail or FICM connectors can cause all sorts of bizarre symptoms.
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Old 07-24-2015, 01:57 PM
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Although i rarley trust the dealer I figured what they said makes sense like the injector harness went bad causing the injector to short. The only reason I took it there was because I don't know of any private shops in my area who could diagnose my problem, I also brought it because I really don't know how to electronically test stuff I have a multi meter but don't really know how to use it, I've read the directions but just don't get it, I have two friends, ones a self proclaimed duramax expert, who after about an hour of looking at it said he would give me more info after doing more research at the dealer he works for and that was two months ago he now ignores my texts or calls, my other friend is an electrician but never has time to help. I heard the insulation cracks or chafes and you can see if its bad or not is that not so?
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Old 07-24-2015, 03:03 PM
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Later tonight I will post some pictures showing you how to test
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Old 07-24-2015, 07:53 PM
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Sorry something came up I'll get those pics tomorrow...
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Old 07-25-2015, 05:10 AM
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I feel like an idiot, in a quick conversation over the phone my friend told me testing these wires is nothing more than checking continuity, so now I guess that's what I'll do today, thank you all again for your input ill let ya kno what I find
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Old 07-27-2015, 06:55 AM
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Well I did find that the #1 injector did in fact short to ground, the injector harness tested ok, I'm just still unsure about the ficm harness, I tried to check continuity of the wires that plug into the injector harness to the plugs that plug into the ficm and it seems like each wire at the injector harness side shows continuity on 2-4 different prongs at the ficm side and I don't know if that's correct or not, I'm thinking since the injector harness itself tested ok the problem must be with the ficm harness, unless the ficm itself could have caused this? Is there a way to test the ficm?
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Old 07-27-2015, 09:59 AM
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The Ficm harness has some wires spliced together, a couple orange/white and some orange/black so what you are finding with the harness is probably OK. Did you check the resistance of the injector coil?
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