can't talk to ecm class 2 issue

DIESELMAFIAPER.LB7

DIESELMAFIAPER.LB7

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Lb7 > lly..... :D

Back to the pos lb7 tho...... I replaced bcm got half as many class 2 codes truck still won't flash not sure if the bcm needs to be programed to the truck first or if they even can where it won't tune the ecm. I'm getting codes for the restraint module believe it's under drivers seat and the carpet.... could that be shorted out?.... I don't have a airbag light on nor does the fix say service air bag?

I got a new fuse block to try our next as well as I had a loose fuse that I tightened up so we had a good connection. But maybe something in there is causing a issue? I'm running out of ideas. Anyone have a diagram of the class 2 stuff or ways to jumper around things to help try eliminating modules
 
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DIESELMAFIAPER.LB7

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well after reading my manuals and testing grounds and power and class 2 wires im not seeing anything out of the ordinary I hate to just keep replacing modules but damn this starting to look like the only thing left to try.

I couldn't find a diagram for the c306 bale connector inside the center console anyone got it handy?

edit:nm found the diag. on here http://www.duramaxdiesels.com/forum/showthread.php?t=16270&highlight=c306
 
DIESELMAFIAPER.LB7

DIESELMAFIAPER.LB7

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no rear dvd u1000 on digital radio receiver and rear seat audio controller that's it now I had lots of others but after I swapped the bcm to a different one and put the original back in they went away also fixed my seat reclining motor and a bad limit switch on the seat to also a b0951 headlamp on indicator circuit and a c0201 for abs enable relay contact circuit
 
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DIESELMAFIAPER.LB7

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circuit 2288 has continuity to pin 2 on the obd2 port so the class 2 circuit is good has around 13-15 ohms resistance between the truck side of the harness and odb2 port cant find if that's in spec or to high?


Edit: I tested it to the rear audio controller I have no connection issue on the class 2 circuit?? also the diag. I found on here is incorrect my manual has the correct diag. lol finally found it
 
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chevyburnout1

chevyburnout1

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So you're saying there is 15ohms of resistance between the ECM and the OBD port? If so that can definitely be your issue. You checked the resistance with everything powered off correct?

And I'm reading the class II data circuit between the OBD port and splice pack 205, is purple circuit #1132. It then turns into circuit dark green #1049 heading to the ECM.
 
chevyburnout1

chevyburnout1

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Ok sounds like you're getting somewhere! However pin 9, circuit '2362' is the "J1939 serial data" circuit, not the class II. You want to check it at pin 58, circuit '1049', which is the actual "class II" data circuit. Very confusing I know. The J1939 circuit is the stand alone data communication between the ECM and the FICM.

Also remember even though your key is off some modules can still be awake and communicating along that data circuit, which can skew your resistance readings. A safe bet would be to disconnect your batteries, just to make sure :thumb:
 
chevyburnout1

chevyburnout1

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Decided to do a little more looking for you as I usually don't make it on here during the weekends. But if you do find your resistance is still high (resistance should be very very low) then check splice pack #205, which I have just noticed, is located right behind your radio. Definitely make sure where that radio adapter module is spliced isn't causing any issues. Chime modules and scotch locks are a no-no ;)
 
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DIESELMAFIAPER.LB7

DIESELMAFIAPER.LB7

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chevyburnout1 said:
Decided to do a little more looking for you as I usually don't make it on here during the weekends. But if you do find your resistance is still high (resistance should be very very low) then check splice pack #205, which I have just noticed, is located right behind your radio. Definitely make sure where that radio adapter module is spliced isn't causing any issues. Scotch locks are a no-no ;)
Click to expand...

Its all plug and play whats connections I needed to put together between aftermarket harness and new deck are soldered

so should resistance be around 1-3 ohms?

Edit: ill check the sp205 again
 
DIESELMAFIAPER.LB7

DIESELMAFIAPER.LB7

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chevyburnout1 said:
The wiring does sound like it's legit. I'm kinda out of ideas for now :(
Click to expand...

Me to I've tried a new ecm, bcm, unhooking anything aftermarket, guess I'll snag a tcm and amp and rear audio controller

Also pin 9 amd pin 20 on the ecm connector had a 0 ohm connection any ideas there? Should it be that way? And for kicks it showed 100ohms going to pin 2 on the obd2 port but nothing to pins 58 or 59?
 
chevyburnout1

chevyburnout1

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Aug 25, 2008
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DIESELMAFIAPER.LB7 said:
Me to I've tried a new ecm, bcm, unhooking anything aftermarket, guess I'll snag a tcm and amp and rear audio controller Being a class II setup I believe you can just unplug all of the unneeded modules on the class II circuit and eliminate the modules as an issue. They are connected in a star pattern so unplugging a module does not break the data communication. However I've never had to do this.

Also pin 9 amd pin 20 on the ecm connector had a 0 ohm connection any ideas there? Should it be that way? Continuity between pin 9 and 20 may be normal or may indicate a voltage short to the circuit on pin #9. Very hard to say as there is no specs for that. That circuit is a direct circuit between the ECM and FICM so I wouldn't think it being shorted would cause erratic ECM operation. Did you measure that resistance with the ECM unplugged?

And for kicks it showed 100ohms going to pin 2 on the obd2 port but nothing to pins 58 or 59? The rest of the resistance sounds normal. Like I said before the data on circuit #9 is completely different and separate from the class II circuit on 58 and 59
Click to expand...

Hope this helps!
 
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