08 lmm with a po341 after rebuild. And no start.

[acprokeith]

Any luck either of you? I'm willing to try anything at this point. Same symptoms and results with an LBZ

Been through the entire truck, harness from sensor to ecm has continuity, 5v signal is there, ground is too. Tried a new ecm, few new cam sensors, new crank sensor (from GM), checked both crank and cam reluctor wheels by hand and by sight (cam with a bore scope). Replaced cam sensor pigtail with one from GM. Just cranks and throws 0340. If you're real lucky you might get a 0341. Nothing bad we can find. Been through all the flow charts, and used the alldata troubleshooting methods.

Found a few chaffed wires that go to other unrelated circuits. Repaired them, although they didn't appear to have been shorting together, or to ground. I'm thinking the cam reluctor wheel may have come loose then stuck/bound itself up on the gear again? Never been into one of these, and was hoping not to, lol.

Got a friend with a scan tool coming by. Will update this with the results. Please post up any ideas or fixes. Thank you. :thumb:

 

[C10Racer]

I'm in the same spot with an LMM; I assume some of these vehicles have started since the beginning of the thread!

Built an '09 LMM and got it all together and we got the P0341 with no other codes. I've monitored the cam signal vs the crank signal with an osciloscope, looked through the cam sensor hole to make sure everything was good and checked the wiring and found no issues. We've changed the cam sensor with no change. This is not our first rodeo; we've built numerous different kinds of engines and specialize in figuring out weird issues but this has me stumped.

This engine was rebuilt after a piston failed and I'm beginning to wonder if the spring in the cam gear was pounded when the engine came apart...could this cause the issue? Anyone?

 

[acprokeith]

I'm in the same spot with an LMM; I assume some of these vehicles have started since the beginning of the thread!

Built an '09 LMM and got it all together and we got the P0341 with no other codes. I've monitored the cam signal vs the crank signal with an osciloscope, looked through the cam sensor hole to make sure everything was good and checked the wiring and found no issues. We've changed the cam sensor with no change. This is not our first rodeo; we've built numerous different kinds of engines and specialize in figuring out weird issues but this has me stumped.

This engine was rebuilt after a piston failed and I'm beginning to wonder if the spring in the cam gear was pounded when the engine came apart...could this cause the issue? Anyone?

You are getting the full cam signal at the right time? I'd bet it's a harness issue. Wire plug should have 5v on one terminal, ground in center, and 5 volts on the other as well (signal to the ecm has 5v on it on mine). Have you looked at the pin out on alldata and checked the harness against it? It is what got me confused. I found 5v on one terminal, ground on center, and nothing on the other. I ASSumed the wire with 5v was my 5v ref signal wire, but it was my ecm (backfeed or whatever). Once I learned via the alldata pinout, that it was actually my ECM wire that had 5v, it wasn't hard to determine that I lost the 5v ref signal.

After days of testing and troubleshooting, along with an intermittent signal from the cam sensor showed on the scan tool, I went back to basics. I jumped the 5v ref signal wire between the engine side of the valve cover bail connector, and the cam sensor connector. Bam it fired up. Seems the 5v signal was lost after it T's off to numerous other sensors, and finally goes to the cam sensor. So I cut the 5v wire on the engine side of the plug (as I figured it might be grounding where broken), and jumped to the cam sensor 5v wire, and tried to start it. Nothing but codes from sensors with no 5v ref signal. This told me that somewhere after that wire feeds 5v to the other sensors, it was broken. It must have a few T's or junctions I can't access. Without tearing the top of the motor off it seemed, I could not find any damage to the wire. We replaced the cam sensor plug and rewired the 5v ref signal to it from the valve cover bail connector. Used sheilded wire and ran it with a little more sense than the factory. Has worked so far with no codes or issues. Hope this helps you or somebody out in the future. I can usually figure these crazy wiring issues out, but this one took 5 days of my time. Wish I would have gotten alldatadiy sooner.

I replaced an ECM that had to be tuned and VIN licensed by ATP and Idaho Rob, yet obviously that wasn't it. Also changed the crank and cam sensor a few times. Gotta say thanks to ATP for getting it tuned and sent out the same day, even after I called in the middle of the afternoon. Then taking it back after I didn't need it, and refunding me all but tuning/time costs. They also let me pick their brains for a good 20 minutes. That says a lot. Glad I used them for my EFI live. Thanks http://atptrucks.com/

 

[C10Racer]

You are getting the full cam signal at the right time? I'd bet it's a harness issue. Wire plug should have 5v on one terminal, ground in center, and 5 volts on the other as well (signal to the ecm has 5v on it on mine). Have you looked at the pin out on alldata and checked the harness against it? It is what got me confused. I found 5v on one terminal, ground on center, and nothing on the other. I ASSumed the wire with 5v was my 5v ref signal wire, but it was my ecm (backfeed or whatever). Once I learned via the alldata pinout, that it was actually my ECM wire that had 5v, it wasn't hard to determine that I lost the 5v ref signal.

After days of testing and troubleshooting, along with an intermittent signal from the cam sensor showed on the scan tool, I went back to basics. I jumped the 5v ref signal wire between the engine side of the valve cover bail connector, and the cam sensor connector. Bam it fired up. Seems the 5v signal was lost after it T's off to numerous other sensors, and finally goes to the cam sensor. So I cut the 5v wire on the engine side of the plug (as I figured it might be grounding where broken), and jumped to the cam sensor 5v wire, and tried to start it. Nothing but codes from sensors with no 5v ref signal. This told me that somewhere after that wire feeds 5v to the other sensors, it was broken. It must have a few T's or junctions I can't access. Without tearing the top of the motor off it seemed, I could not find any damage to the wire. We replaced the cam sensor plug and rewired the 5v ref signal to it from the valve cover bail connector. Used sheilded wire and ran it with a little more sense than the factory. Has worked so far with no codes or issues. Hope this helps you or somebody out in the future. I can usually figure these crazy wiring issues out, but this one took 5 days of my time. Wish I would have gotten alldatadiy sooner.

I replaced an ECM that had to be tuned and VIN licensed by ATP and Idaho Rob, yet obviously that wasn't it. Also changed the crank and cam sensor a few times. Gotta say thanks to ATP for getting it tuned and sent out the same day, even after I called in the middle of the afternoon. Then taking it back after I didn't need it, and refunding me all but tuning/time costs. They also let me pick their brains for a good 20 minutes. That says a lot. Glad I used them for my EFI live. Thanks http://atptrucks.com/

At the right time I can't confirm 100% but it does APPEAR to be at the right time; I'm trying to get a-hold of another LMM for testing. On the harness I'm getting 5V on both outside terminals and 0V in the middle and we are getting a BEAUTIFUL signal from the cam sensor at the ECM; I've overlaid the signals from and cam and the crank and they look great. We have compared 5V reference voltage from the cam and crank sensors and also found no anomalous readings there.

We've got prodemand here which is Mitchell's version of Alldata and have run pinout tests throughout the system and have found zero anomalies.

 

[acprokeith]

At the right time I can't confirm 100% but it does APPEAR to be at the right time; I'm trying to get a-hold of another LMM for testing. On the harness I'm getting 5V on both outside terminals and 0V in the middle and we are getting a BEAUTIFUL signal from the cam sensor at the ECM; I've overlaid the signals from and cam and the crank and they look great. We have compared 5V reference voltage from the cam and crank sensors and also found no anomalous readings there.

We've got prodemand here which is Mitchell's version of Alldata and have run pinout tests throughout the system and have found zero anomalies.

Been thinking about this. Has the cam's reluctor wheel spun possibly? Getting 2 pings from the crankshaft sensor for every 1 of the camshaft? I know they come loose on the LBZ's, but I haven't seen how the LMM's work. Curious about this spring you mentioned too.

Mine would have cam signal and then loose it, but never would start. Seems it want's to see the signal a few times at the same-ish speed before it fires the injectors. Not sure on the details though. We typically got 3-4 good "pings" off of it, and then nothing.

I'd take the ECM out of the other truck and try it. Try yours in it. At least it will rule it out. It can't be the sensor, or the wiring (it appears), so it has to be the ECM or a mechanical issue between the sensor and camshaft. At least that's what would make sense.

Seems these Duramax's make you earn the chit eating grin they put on your face. Mine was a brain bending, 100's of open ended threads reading, PITA.

 

[rddooley92]

Sorry guys just seen your post. Ended up removing the engine and installing another. I tried absolutely everything. I suspect if I tear the engine down I would find damage to the cam shaft. The engine turned over abnormally slow like it was tight. The wavelengths on the labscope where out of sync. So even though it had cam signal it would not fire. Hope you guys have better luck.

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[C10Racer]

Sorry guys just seen your post. Ended up removing the engine and installing another. I tried absolutely everything. I suspect if I tear the engine down I would find damage to the cam shaft. The engine turned over abnormally slow like it was tight. The wavelengths on the labscope where out of sync. So even though it had cam signal it would not fire. Hope you guys have better luck.

Sent from my SM-G935V using Tapatalk

What do you mean the wavelengths where "out of the sync"; I've been trying to find any kind of info about what the wave forms should actually look like. This engine spins great; just won't fire!

 

[C10Racer]

Been thinking about this. Has the cam's reluctor wheel spun possibly? Getting 2 pings from the crankshaft sensor for every 1 of the camshaft? I know they come loose on the LBZ's, but I haven't seen how the LMM's work. Curious about this spring you mentioned too.

Mine would have cam signal and then loose it, but never would start. Seems it want's to see the signal a few times at the same-ish speed before it fires the injectors. Not sure on the details though. We typically got 3-4 good "pings" off of it, and then nothing.

I'd take the ECM out of the other truck and try it. Try yours in it. At least it will rule it out. It can't be the sensor, or the wiring (it appears), so it has to be the ECM or a mechanical issue between the sensor and camshaft. At least that's what would make sense.

Seems these Duramax's make you earn the chit eating grin they put on your face. Mine was a brain bending, 100's of open ended threads reading, PITA.

The reluctor wheel bolts to the cam and the gear is pinned to the cam so I don't THINK it could have spun. We've tried nearly everything and even compared out cam signal to another truck and they both look good.

About the only thing I even have a question about now is the alignment of the reluctors. The small notches on the cam reluctor seem to make a waveform very similar in size to the bigger notch on the crank reluctor and it would make some sense they're supposed to line up but in this case they don't when the cam and crank are lined up...does anyone know if they're supposed to?

 

[2004LB7]

I kinda thought that these engines could run with one good sensor and the bad one removed. but if there is any issues when both are installed the engine won't start.

If this is true, then couldn't you just try and remove one of the sensors and see if it starts?

 

[C10Racer]

I kinda thought that these engines could run with one good sensor and the bad one removed. but if there is any issues when both are installed the engine won't start.

If this is true, then couldn't you just try and remove one of the sensors and see if it starts?

Nope; to my understanding and from what we've experienced the LMM and the LBZ will ONLY start with a good-clean cam signal. They will RUN if the cam sensor goes bad while running but they won't restart again.

 

[C10Racer]

We found it; the oil pump drive gear had broken loose on the crankshaft and spun when the balancer broke it's dowel as the piston came apart. LBZ and LMM guys with P0341 codes after rebuild check to make sure your oil pump drive gear hasn't broken it's dowel!

 

[IOWA LLY]

Uh... Not to be a dick, but how did you “rebuild” an engine without removing that gear???



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