Project C4, 85 Corvette

[Steve85]

Old wiring and grommet removed.

The wires that are still there are the VSS wires, oil pressure and fan relay ground and one or two others not sure where they go. All other underhood wiring goes through a connector on the driver side and is untouched for this swap (and when putting the DFI in some years ago)



To help with feeding everything from inside the car to the engine bay, I ziptied connectors to wires. This way as I gently pulled things through, the wires didn't "double back" as connectors got stuck at the firewall. The entire harness behaved more like one wire than a bunch of separate loose wires.




Once I got everything fed through I went to work identifying the wires I needed to tap into. Most go right through this - Connector 237



As I identified the wires I needed I labeled them with names and numbers and corresponding names/numbers on the PSI harness.



I connected everything without regard to where anything would be mounted or wires would ultimately be run for testing purposes. I wanted easy access to all wires and connections in case anything was wrong. It was kind of a mess in the footwell to be honest.

The car drove great so it was time to find a permanent mount. I tried squeezing it into the same place the old ECM came out but the new PCM is too thick and the much larger connectors interfered with the HVAC blend door.

Under the seat we go!

I cleaned up all the wiring that I needed to tap into.



Then pulled back the footwell carpet and ran the main harness through there and cut a slit in the carpet under the seat.





After that, it was just a matter of connecting the right wires, number coordinated, connecting the PCM connectors and tucking the underdash stuff up behind the knee bolster where it came from.

Patience with numbering wires is crucial to making sure the connections are right. Trying to remember colors or trying to read whatever abbreviation you wrote at midnight after only 4 hours a sleep the night before can be frustrating :willy:

I think if were to do it again though, I'd keep the PCM under the hood as in the later model cars and what ch@os is doing.


C237 pinouts defined and PSI harness connections: