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Hey, I’m having similar issues with an 08 enclave. Installed a reman engine and trans (old engine had some extra holes in the block) lol. Went to fire it up, no coms with ecm/tcm/ebcm. But I do have coms to bcm. Im getting 12v to the ecm “battery positive” pin on the x1 connector, the x2 connector has the ground (from what I can gather of these wiring diagrams) and when measured across to a ground, I’m getting 6 ohms. I’m new to troubleshooting wiring issues so excuse my ignorance but what’s my next step? Is 6 ohms an issue?
I moved your question to your own thread so as to not muddy up the waters so to speak.
If you have one lead of the ohm meter on the computer ground and one lead on battery ground and measuring 6ohms, that is a problem.
As Noah said, I would check the grounds. Ensure they are clean and nothing is disconnected. Especially if this condition is coincident with the engine replacement.
My information may be off because I have wiring diagrams for a 2010 model, with the 3.6L. But if you have the same options it should apply. There are two grounds for BCM.
Connector X3: Pins 1 & 5 (blk/wht wires) go to G301, located under the left dash kick panel.
Connector X4: Pin 9 (blk wire) is direct battery ground.
Somehow I doubt that is your problem though. If ecm/tcm/ebcm are the only quiet modules, I would direct your testing toward EBCM. Based on my understanding, the enclave uses a serial comm network that starts at BCM and splits two ways, flowing through modules sequentially. For a visual:
.ecm<tcm<ebcm<----*BCM*---->vcim>fpcm>rdccm.
If any one module is dead or lose power/ground, the modules the follow after will also not communicate. I hope that visual helps. 1. Double check your BCM powers and grounds. If those are good 2. Check your EBCM powers and grounds.
tbmfix wrote: If any one module is dead or lose power/ground, the modules the follow after will also not communicate. I hope that visual helps. 1. Double check your BCM powers and grounds. If those are good 2. Check your EBCM powers and grounds.
I agree with tbmfix here. I have seen a couple no-crank conditions caused by an open in the network as you describe on this generation GM after engine replacement.
Usually , the EBCM (abs module) connector is not seated well creating an open in the network circuit. Usually unlocking and locking the connector does the trick, unless a pin has been bent. I don't think a missing power or ground at any particular module would open the network in the same way.
I didn't want to send the OP that direction just yet because of the excessive resistance reported, but you do bring up a good point here.
Usually , the EBCM (abs module) connector is not seated well creating an open in the network circuit. Usually unlocking and locking the connector does the trick, unless a pin has been bent.
Came in to say this. If you dropped the powertrain to do the engine/trans swap, and you took the harness with the powertrain, then you had to have unplugged the EBCM.
Getting the EBCM connector fully latched can be harder than you'd think. Especially if someone has been there before and broken off some of the latching tabs on the EBCM itself...
I don't think a missing power or ground at any particular module would open the network in the same way.
I always thought that the downstream modules wouldn't be impacted by a module missing a power feed, since there's still continuity "through" the module.
But I'm not confident about that! Could be way off.
I don't think a missing power or ground at any particular module would open the network in the same way.
I always thought that the downstream modules wouldn't be impacted by a module missing a power feed, since there's still continuity "through" the module.
I agree. A missing Power should not affect downstream modules. However, because each module supplies a 2.5 volt bias to the CAN bus, a missing/bad ground can affect the network. A missing/bad ground can produce an elevated bias voltage, corrupting the whole network.
"Knowledge is a weapon. Arm yourself, well, before going to do battle."
"Understanding a question is half an answer." I have learned more by being wrong, than I have by being right.
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