Lb7 is winning the battle

clrussell

clrussell

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elliottw said:
I know you're extremely well versed in dmaxs but have you tried batteries? In my tech days I also had failed fuse boxes do some inexplicable shit... years of mouse piss etc just ate them from the inside out. Just throwing some stuff out there... hate electrical gremlins.
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Nope, no new batteries however they are pretty new. I don't see any fuse box problems with it, power comes out and stays as it should

Cluster holds battery and ignition voltage while failing. Just verified with the lab scope on both leads at the same time.
 
Chevy1925

Chevy1925

don't know sh!t about IFS
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clrussell said:
Nope, no new batteries however they are pretty new. I don't see any fuse box problems with it, power comes out and stays as it should

Cluster holds battery and ignition voltage while failing. Just verified with the lab scope on both leads at the same time.
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when the truck is running, do the interior lights flicker at all?
 
clrussell

clrussell

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Is this the data line resistors?

b293128da6cd058ed47e6b8363c4fe48.jpg



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DAVe3283

DAVe3283

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I think that is just a sealed splice pack.

This may sound counter-intuitive, but I would try a known-good ECU and FICM. If one of them is sending garbage data on the bus, it can crash the cluster, which then holds the data bus low (disabling it unintentionally). Technically a programming bug in the cluster, but we can't fix that, so try an ECU + FICM that are known to work perfectly, and avoid triggering the bug.

That should be an easy test (start with ECU) if you have the parts laying around.

I wish I was out there, I would slap a protocol analyzer on the bus and see exactly what happens right before the failure.
 
clrussell

clrussell

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DAVe3283 said:
I think that is just a sealed splice pack.

This may sound counter-intuitive, but I would try a known-good ECU and FICM. If one of them is sending garbage data on the bus, it can crash the cluster, which then holds the data bus low (disabling it unintentionally). Technically a programming bug in the cluster, but we can't fix that, so try an ECU + FICM that are known to work perfectly, and avoid triggering the bug.

That should be an easy test (start with ECU) if you have the parts laying around.

I wish I was out there, I would slap a protocol analyzer on the bus and see exactly what happens right before the failure.
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I've put a known good ficm on it, have not tried an ecm but I can put mine on it
 
clrussell

clrussell

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Also, data line goes to low voltage when problem occurs, unhook cluster and it comes back up
 
DAVe3283

DAVe3283

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clrussell said:
Also, data line goes to low voltage when problem occurs, unhook cluster and it comes back up
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So we know the cluster is holding the bus low (crash / bug). We just don't know why. Since you've tried a known-good cluster and it does the same thing, that means that some message or signal to the cluster is triggering a bug in the firmware.

Your big possibilities are bad data on the data bus crashing it (as I speculated before), or some other signal out of range crashing it (voltage dropout on one of the pins or something). Since you have verified the voltage isn't dropping out when the problem happens, I still strongly suspect some garbage message(s) on the data bus that crash the cluster.

If swapping ECUs doesn't fix it, then you have to break out the logic analyzer and start the real hard work. Hopefully a different ECU (and fresh clean OS/tune) fixes it.
 
clrussell

clrussell

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DAVe3283 said:
So we know the cluster is holding the bus low (crash / bug). We just don't know why. Since you've tried a known-good cluster and it does the same thing, that means that some message or signal to the cluster is triggering a bug in the firmware.

Your big possibilities are bad data on the data bus crashing it (as I speculated before), or some other signal out of range crashing it (voltage dropout on one of the pins or something). Since you have verified the voltage isn't dropping out when the problem happens, I still strongly suspect some garbage message(s) on the data bus that crash the cluster.

If swapping ECUs doesn't fix it, then you have to break out the logic analyzer and start the real hard work. Hopefully a different ECU (and fresh clean OS/tune) fixes it.
Click to expand...

I've got an ecm in it right now, going through the relearn for security and then I'll flash it if I can.

The ecm in this truck looks brand new and says remanufactured, however it does not have a name on it.
 
NC-smokinlmm

NC-smokinlmm

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You need a data bus analyzer. Double check the ground to the cluster, load it with a little light bulb. Lol... Also, look at the fuse panel as said before, I've seen an lbz do some wierd shit and it had a warped underhood fuse panel.
 
clrussell

clrussell

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NC-smokinlmm said:
You need a data bus analyzer. Double check the ground to the cluster, load it with a little light bulb. Lol... Also, look at the fuse panel as said before, I've seen an lbz do some wierd shit and it had a warped underhood fuse panel.
Click to expand...

Did both.


Put my ecm in it yesterday about noon and it hasn't failed since.. fingers crossed this thing is fixed
 
DAVe3283

DAVe3283

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That's a tough one, for sure. Be sure to tell him how the other shop caused the issue, and how tricky finding it was. But bill something more reasonable. You should get a lot of good will, and be remembered as that smart shop that can fix anything.

I don't know what a reasonable number of hours to bill would be, though...

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