coryfitz78

Just a few questions about harness re-working. Using an 07 Trailblazer SS harness for an ls swap into an 86 chevy truck. The harness is 95% completed, but I have a few questions about it. The VSS signal has two wires going to the ecu, one green/white pin 39 and the other is yellow/black pin 24, my question here is which one should I use for ecu signal/voltage supply? #2 is the signal for the tach, can I use the white wire labeled for engine speed signal? Thanks in advance!

Mike_hawk

I'm not sure on the pinouts for that vehicle, but both wires from the VSS go to the PCM, there should be a separate wire for vehicle speed coming from the PCM that's the one you run to your speedo. The Tach signal usually requires a 12vpower wire with a resistor to read accurately. If you haven't already you should look at lt1swap.com there is loads of helpful info there.

coryfitz78

Yeah that's a great site, unfortunately there's not alot of info out there about modifying the e67 ecu and harnesses. Luckily for me, I was able to pull wiring diagrams from ALLDATA. The older harness builds are much easier to re-work, and you don't need a magnifying glass to see the connector pin outs lol

EFIHARNESS

On the E67 We use J1-25. Be sure to set the tach output to crank in the cal, as the oe setup is designed for can buss guages.Steve

coryfitz78

Will do, thanks!