Tuned lly duramax no added power between tunes

[shakenfake]

Sounds like a classic GMT800 issue. I've never come across it but 03-05 trucks I am always hearing stories on how they don't like to take tunes and require the PCM/ECM pulled and benched.

 

[JoshH]

There is a com wire connector under the dash near the I/P fuse box above and behind the park brake release called SP205. All the data wires for all the modules are tied together in that block with a jumper cap. It is, IIRC, a 2x6 connector with a white cap. If you pop that cap off and jump wires B and D, you basically just made a bench harness and isolated the ECM to the OBD2 port. I do this to every LLY and LB7 I flash now because almost all of them have some sort of aftermarket electronics gizmo that causes hell with flashing.

 

[Chevy1925]

^^^ 100% this. We have a bench harness to do it but that’s a hell of a lot easier the way Josh is saying.

 

[Tactical Camel]

There is a com wire connector under the dash near the I/P fuse box above and behind the park brake release called SP205. All the data wires for all the modules are tied together in that block with a jumper cap. It is, IIRC, a 2x6 connector with a white cap. If you pop that cap off and jump wires B and D, you basically just made a bench harness and isolated the ECM to the OBD2 port. I do this to every LLY and LB7 I flash now because almost all of them have some sort of aftermarket electronics gizmo that causes hell with flashing.

Thanks boss, I will give it a go today.


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