Hello, I bought an LT4 out of a totaled 2016 Z06 Vette. I got the engine, complete vehicle harness, ECM, PWM fuel pump module, fuel tank with OEM PWM fuel pump, stainless fuel line with pressure sensor, gauge cluster, Electric power steering rack, lower column cover with the keyfob slot, both keyfobs, cooling module with radiator, A/C condenser, Supercharger coolant pump, radiator, & a box of assorted modules. What I am trying to do is make a stand alone harness to put this engine into my 81 Camaro Z28, I will be using a standard transmission, I have narrowed down to a Tremec T56 Magnum, Richmond Gear 5 speed or Gforce. The engine came with a McLeod twin disk clutch. I laid the entire vehicle harness out on my garage floor, plugged everything in, connected all the grounds together, and hooked a battery up. I get nothing when I press the start button. I was not expecting it to start, but I expected the ignition to come on & power up the gauge cluster. I probed the fuse block & got the gauge cluster to come on, but that's it. From what I have been reading in various forums. I need to disable the VATS/Anti Theft in the ECM. But when I plug my scan tool into the OBD connector, I get no communication with the ECM. So I built a bench programming harness, and successfully powered up the ECM. I used my son's HP Tuner, bought 2 credits & was able to disable the VATS. I connected everything back up, still nothing. I want to get the ignition to come on & the gauge cluster to power up. Once I am able to do this, then I plan on building the stand alone harness. The problem is there is no information out there on how to build the actual stand alone harness. There are plenty of people out there who will build the harness for you for $$$. I just cant see paying a bunch of money to have someone cut open the harness, remove all of the unused connectors & put it back together. I was just at the Fall Carlise Swap Meet last weekend & picked up a bunch of braided split loom harness covers in various sizes, heat shrink, etc. I have everything to do the job, I just need the basic instructions on how to do it. I would like to retain the gauge cluster, but I dont know it it runs off the ECM or do I need to retain the body control module also in order to make it work. I would greatly appreciate any info.
Thank You

Got the gauge cluster to power up by jumping the fuse block






Bench programming harness


Communication with the ECM

 

If you are not getting any comm with factory harness, you may need to jumper the trans connector CAN four pins. CAN Hiigh to High and Low to Low.. Older 6L80e send the CAN data down to the TCM, and back up to the rest of the harness. So if you unplug the trans, you won't get any data as the loop is open. Just a suggestion.

 

It's not an automatic, The engine came out of a 2016 Z06 Vette with the 7 speed manual. Does the manual trans still use a controller ?, I went to the shop where I bought the engine from and got the transmission harness, which runs from the underhood fuse block back to the rear of the car. I plugged it all in & still getting nothing. There are still a bunch of modules missing from the harness. I will look over all of my Alldata electrical diagrams that i have printed out and jumper the can bus wires if I have them. Thank you. I cant believe there is no instructional info out there that tells you how to modify the factory harness to build a stand alone harness.

 

I found the transmission controller & cut & looped back the canbus wires, still nothing. I must be missing something obvious. When we have a car in the shop, we can start & drive them with seats, doors, etc all removed. I have everything electrically here & connected that should let the ignition come on. Plus I have disabled the VATS /Antitheft on the ECM with HP Tuners.

Transmission controller canbus looped back

 

I found the transmission controller plug & looped back the canbus wires, still nothing. I have driven cars around the shop with doors, seats, consoles, radios, etc out of them & they still start & run. I used HP Tuners to disable the VATS/Antitheft. Electrically everything is connected that shoul make the ignition switch on, and crank the engine.

Transmission controller canbus looped back

 

lt1swap.com has some info on converting a truck Gen5 harness. Much of it is likely similar. Also you can go to acdelcotds.com and for $20 get a 3 day subscription and be able to view/print all the factory service manual data for the car that engine came from (or any other car you wish). Its way better than alldata. I would go there and look into the data communication schematics for that vette to see whats potentially missing.

 

I attempted to post a reply twice, but I got a message saying it needed to be reviewed ??, I'll try again

 

So I found the transmission control module connector & looped back the canbus wires, still nothing. When I connect the battery I can hear the Hazard relay clicking like someone broke into the car. When I press unlock on the key fob it stops. I have driven cars in & out of a shop without doors, seats, console, dash etc. they still start & run. Electrically everything is present.

 

 

My reply with pictures still has not gone up. I keep getting messages that it needs to be reviewed by a moderator. How long does this take ??. Is there a limit to the amount of pictures that can be uploaded ??

 

You only have 4 posts to your name up to this point. That is why.

 

Check your battery voltage. A low voltage situation can play havoc with a Vette. So many stupid computers and electronics that a slight low voltage condition will mess with everything. Highly unlikely here with theft control showing up, but worth a try.
Looking at the pics, if the fuel pump gets command and turns on, your gonna have a mess…if there’s fuel in the tank. Maybe fuel level or tank pressure has something to do with this? Totally guessing here! Tank is prolly empty?

 

 

The battery is fully charged & I have a trickle charger on it. The fuel tank is empty. I have it connected because I wanted to hear it power up. When I connect the battery to the harness, I can hear the fuel pump run for a couple of seconds. So after I spent another weekend looking over the harness & probing fuses in the fuse blocks, checking for blown fuses, etc. I moved onto plan B. I have cut the harness open & am removing everything I dont need. Starting from the back of the harness (rear of car). I am keeping everything that runs to the fuel pump controller, VSS sensor connector, transmission oil temp connector, etc. Since I am getting rid of the rear fuse/relay block that goes in trunk, I re-routed the fuel pump supply wire to the front fuse block, and using the 30 amp electric parking brake wire to feed the 30 amp fuel pump wire. The main reason I wanted to try & work with the OEM harness is that I wanted to retain the Gauge cluster. So now I will retain the gauge cluster harness & see if I can get it to power up.
I have been trying to post addl pictures, but they don't go up. I keep getting messages that they need to be reviewed by a moderator, which has been over a week ago. Someone responded & said I have only 4 posts, but I dont understand what that has to do with me posting pictures. Evidently there is a limit on how many pictures you can post ??, I am on other forums & have not had this problem.

 

It has to do with how new a member you are. There is a threshold of post #'s you need to pass before you can do pics. It's how they keep trolls out.....

 

oh I see, that explains it, I knew there had to be an explanation