Trigger Wiring in Piggyback Setup

[CurtisL]

I'm currently wiring up my Crank and Cam trigger signals on an LS6 (similar to LS1) in a piggyback configuration with the factory ecu and had a quick question. 

I'm planning to run a trigger signal wire and signal ground wire in a shielded cable to the Link ECU. I plan to allow the factory ecu to supply the +12V supply power as is done in the factory application, and then splicing the factory signal wire to the signal wire going to the Link ECU.

Currently it appears that the factory ecu has a pullup resistor according to the factory schematics. Would this work appropriately as long as the pullup in the Link ECU was disabled so that there are not two pullup resistors on the same signal wire?

 

[Adamw]

Yeah that should be fine.  You will likely need to connect the sensor ground between the two ecu's also.

[CurtisL]

Thanks Adam, I was curious about tying the signal grounds together, but I also didn't want to create ground loop issues or anything. The factory ecu and the link will be grounded to the same location, so I wasn't sure if that was good enough. 

[Adamw]

I have seen more problems when the sensor grounds arent connected than when they are, so I would connect them - or at least make provision for them to be connected if you do run into problems later.  Some factory ecu's use a differential input trigger circuit so the crank sensor "ground" is isolated from ecu ground - I have only personally seen it on ecu's that use reluctor sensors but dont do enough piggybacks to know if it is done in GM ecu's.