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View Full Version : LBZ standalone harness....is there any reason to keep the Class 2/J1850 wiring?


DURAtotheMAX
March 14th, 2013, 03:12 PM
Ive made a handful of LBZ standalone wiring harnesses for customers doing LBZ duramax swaps into various other vehicles.

Im working on my latest standalone harness right now, and as Im doing the splicing/wiring for the OBD port, it occurred to me...is there any reason to keep the Class 2/J1850 wiring in the harness and OBD port? Obviously theres not going to be any factory GMT-800 cluster/BCM/TCSM/etc used in standalone applications. ECM/TCM flashing and scanning/datalogging is all done directly over high-speed GMLAN.

As far as I know, the only single thing Class 2 is used for on the LBZ's is so the ECM and TCM can communicate with the cluster and BCM for various body functions/cluster info.

Theoretically making it (class 2) useless in a standalone application.

I just like to make my standalone harnesses as simple and paired down as possible. And if Class 2 isnt needed for anything in a standalone application, I figure thats yet another couple wires I can just get rid of.

Any ideas Ross?

thanks
Ben
THEFERMANATOR
March 14th, 2013, 03:46 PM
Possibly could cause issues with aftermarket cheap scanners and code readers.
GMPX
March 14th, 2013, 04:50 PM
Sound right Ben, there isn't anything we do for scanning and programming on the J1850 bus for the LBZ.
THEFERMANATOR
March 15th, 2013, 03:18 AM
Could it be an issue if say somebody was using a scanguage or CTS as a set of guages for gear display? I know some people who do swaps use the scanguage and CTS for guages since they don't have a cluster.
DURAtotheMAX
March 16th, 2013, 05:48 AM
Could it be an issue if say somebody was using a scanguage or CTS as a set of guages for gear display? I know some people who do swaps use the scanguage and CTS for guages since they don't have a cluster.

No, because the LBZ ECM doesnt do any scanning/data read out over Class 2.

The only thing the LBZ ECM uses Class 2 for is sending info specifically to the cluster, and to the BCM for anti-theft stuff. It doesnt send out "scan tool data" over Class 2.
THEFERMANATOR
March 16th, 2013, 02:07 PM
No, because the LBZ ECM doesnt do any scanning/data read out over Class 2.

The only thing the LBZ ECM uses Class 2 for is sending info specifically to the cluster, and to the BCM for anti-theft stuff. It doesnt send out "scan tool data" over Class 2.


What about gear display data and other generic info that say a CTS would read out?
DURAtotheMAX
March 16th, 2013, 02:59 PM
What about gear display data and other generic info that say a CTS would read out?

thats all over GMLAN (CAN) on the 06+ trucks. If EFILive and the tech 2 reads data and codes/scans over GMLAN (CAN), why would other scan tools be any different?

Class 2 is only used for the GM-specific (IE, the "proprietary" messages) messages to the body modules (including the cluster) on 06+ trucks. Its not used for the generic SAE/CARB/EPA data logging/scanning.

Even on the older trucks, as far as I know, the cluster doesnt actually just pick up the "generic EPA-mandated scan tool" PIDS over the databus...for example, I think the 05 and older ECM's actually broadcast two different "coolant temp" messages for example. One message-broadcast being a generic "scan tool" information (for generic scan tools, emissions testing, EPA-required stuff etc), and the other message is a GM-proprietary message specifically directed at the cluster.....I THINK.