Still having trouble, need recomendations

cjbennett1984

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Sep 3, 2021
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2006 lbz with 245k miles 4x4, lifted 6", PPE tuner, cat delete. Started getting injector codes. Replaced Injectors with new stock injectors. At first start up ran like new for 30 min. Then clattering. Clear the codes and again the truck ran like new for about 10 miles then the process continued. Attempted the ice pick fix as we were getting 0201 and 0204 codes with 2146. Replaced the pigtails for those two cylinders. No improvement. Eventually purchased a new engine harness. After installing new engine harness, the problem persists. Ohm'd out the old harness to verify continuity from the bail connectors to the ECM. No open or high resistance circuits. All wiring appears to be good. However, we learned the truck runs perfectly until it warms to a point of malfunctioning. At this point the only thing left to replace or check would be the ECM. Heard that gmc does not stock them and they are back ordered. Is replacing the ECM the next step? Who is the right resource of an ECM of this model? Does it have to be flashed by a dealer. I put this truck back to the stock tune attempting to clear this issue. Is it possible my stock tune got botched? Or is this just a symptom of my ECM failing? Thanks in advance
 

cjbennett1984

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Sep 3, 2021
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The codes are not consistent. But generally are 0201 0204 and 2146.
There have been times when I got 2149 as well. But only once or twice. I think the codes are very vague and not as direct as I had hoped for.
 

cjbennett1984

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Sep 3, 2021
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These are the balance rates for the injectors after the truck warms up. 15-20 min at idle. They are all within spec and look great beforehand.
 

cjbennett1984

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Sep 3, 2021
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Thanks. For the trouble shooting guide. Good to know we did our due diligence. I contacted a local ecm company this morning here in Houston and they willvtest mine for 100$ and rebuilditbif required. So at least I can check that component off the list. Appreciate the support. BTW. The pigtails for the lbz injectors from gmc have to be modified, and the oem harness does not fit my glowplug control module without similar modifications. Thanks again. Pictures can be provided if requested.
 

cjbennett1984

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He's, we put brand new Bosch injectors in the truck, then we replaced the engine wiring harness, still the same. So we swapped #3 and #1 injectors as they are on different banks. (Same side different banks). And number 1 & 4 were still showing issues. So we identified the curcuits and ohm'd them out to the ECM. no high resistance circuits. So now I have the ECM at a local specialist that is testing it and will rebuild it if found broken. We experienced a perfect trunking truck until it warmed up and then it would run really rough and show the irradic balance numbers. But upon cold start the balance rates all look great. Hard to tell spent over 4k already and probably 40 hours of labor.
 

Ron Nielson

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Oct 11, 2009
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I wouldn't be too quick to condemn the ECM as the source of the problems. The ECM pulls the signal voltage down at the FICM (same as EDU in the wiring diagrams) and the EDU connects to the injectors via the wiring harness. Since you have a good balance (good injector firing) while the engine warms up, things look A-OK until the warm-up point, then something is lost, the DTC suggesting possibly an open circuit. So maybe a pin fitment problem that opens up when the engine warms up or a failure in the EDU itself. There have been lots of EDU/FICM failures posted on this forum and others. have attached the closest wiring chart I can find for the truck, but not specific to LBZ. I know that by the LMM era, the ECM directly fired the injectors, not sure about the LBZ.

For $100, it's probably worth the investment in having the ECM checked and repaired if necessary. I hope they find something and repair it so you can get your truck back to running as it should. Best of luck to you.
 

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cjbennett1984

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Thanks for the support, I had a sit down with the secretary at the shop. Every question she would go to the back and ask then come back. Took much longer than necessary, but she relayed the information and indicated that they have s÷n this before and that it could be possibly a bad "cap", which I interpreted as a "capacitor". Buy I suspect she didn't. In any way, it is a process of elimination. I know they want money and since I am offering to give them some, they will say and do what they need to to make it happen. But if that fixes it at this point i will gladly pay. Just starting to wonder if I prematurely replaced the injectors. I was told to expect to replaced them at 200-250k. A co worker of mine just told me that his 2009 power smoke just rolled over 300k and they have not had any problems with injectors. So I am not sure. This is my first experience replacing injectors. I can honestly say that I really didn't enjoy the cost or the back breaking effort. Even if the overhead creeper made a tremendous difference. The tight spaces and odd routing with so much accessories that had to be removed made the whole job much less fun. I am grateful for the support I have been afforded though. Can't imagine what this would have cost to have done at a repair shop or dealership.
 

2004LB7

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Dec 15, 2010
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I wouldn't be too quick to condemn the ECM as the source of the problems. The ECM pulls the signal voltage down at the FICM (same as EDU in the wiring diagrams) and the EDU connects to the injectors via the wiring harness. Since you have a good balance (good injector firing) while the engine warms up, things look A-OK until the warm-up point, then something is lost, the DTC suggesting possibly an open circuit. So maybe a pin fitment problem that opens up when the engine warms up or a failure in the EDU itself. There have been lots of EDU/FICM failures posted on this forum and others. have attached the closest wiring chart I can find for the truck, but not specific to LBZ. I know that by the LMM era, the ECM directly fired the injectors, not sure about the LBZ.

For $100, it's probably worth the investment in having the ECM checked and repaired if necessary. I hope they find something and repair it so you can get your truck back to running as it should. Best of luck to you.
LB7 and LLY used the FCIM to fire the injectors. LBZ and above the driver circuit was integrated into the ECM
 

Ron Nielson

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Oct 11, 2009
308
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Berryton, KS
LB7 and LLY used the FCIM to fire the injectors. LBZ and above the driver circuit was integrated into the ECM
I wondered why the 2003 and BYD wiring diagram from GMUPFITTER didn't have a separate diagram for the LBZs included. Sometimes you just don't know what you don't know. Thanks for the help.
 

2004LB7

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I wondered why the 2003 and BYD wiring diagram from GMUPFITTER didn't have a separate diagram for the LBZs included. Sometimes you just don't know what you don't know. Thanks for the help.
when they made those diagrams and other documents they probably thought they where going to be able to use them for many more generations. then injector problems, emissions regulations, etc made them obsolete pretty quick.

once they made the switch to LBZ new electrical diagrams where made. there are probably other reasons too but thats my take
 

cjbennett1984

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Sep 3, 2021
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We took pictures of the bail connectors and ohm'd out the circuits for the injectors found the comons and the dedicated lines. If you look close at the pictures we wrote the cylinder designations on them. The small bail connector is for one bank, the larger one is for the other bank. We ohm'd out the circuits from the bail co newton's to the ECM as well. I am hoping to hear from the repair shop on Monday or Tuesday. 20210904_155716.jpg
 

2004LB7

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the other side of the connector is the side that typically has the issues. the pins get bent or pushed back into the connector when inserting it
 

cjbennett1984

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We checked them thoroughly and used contact cleaner to ensure a clean connection. That was the low hanging fruit we were hoping to find early, without success. The engine harness has been replaced and the problem persists. If the ECM shows no issues we can check resistance from the ECM plug thru the injector before and after warming the engine up.
 

cjbennett1984

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GoECM called today and explained that some caps were out and something to do with the battery contacts were bad as well. In an case they were able to repair the ECM and it is ready to go. As soon as I can get there after the huricanne. I will update.
 

cjbennett1984

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LDS called to confirm they received my core exchanges on the injectors. They have been aware of the issues we have been experiencing and offering support where they could. They also though I might like to know that the oem injectors I sent them from my truck were LLY injectors. They seem to think that my truck will run much better with the Correct injectors.. but I am not so sure about that.. I think they ae pretty much the same. Only the taper is a little different on the body. I heard the LLY can fit into an LBZ head. But the LBZ can't fit into the LLY head. Anyway I expect to put the ECM in the truck this evening and hope that puts an end to this issue.
 

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