Wiring harness and ECU from p-body to l-body?

[Pandemoniac]

Thought I'd ask this question after running into some PITA issues here. A guy that's bought a lot of parts from me would like my wiring harness and ECU out of my '89 shadow. He has an L-body that he wants to use the newer ECU on. I've detatched the whole harness from under the hood, but running into a real pain in the --- trying to remove the harness in one piece, without removing the entire dash.

Is there any benefit to going with the SMEC and harness from a P-body for an L-body? Looking at the mess under the dash, I have serious doubts this can be adapted to the older platform very easily, and am not really understanding the reason to switch to the SMEC if the older LM can be re-calibrated for a 3 bar tune etc. in much the same way.
Help me out, should I use my limited free time to keep trying to dig deep into this thing, or discourage trying to use this whole mess in an Omni or charger platform?

[cordes]

I wouldn't use a P body harness unless you want a lot of work. Minivan harnesses are a lot easier from what I've read. If I'm not mistaken the P body cars don't have the block on the drivers side which connects the under hood and in car sections of the harness. I know that's the case in 90' for sure.

Anyway, I would go with megasquirt or equivalent before I went to a non-LM harness in an L body.

[jonnyb]

I used an 88 ES Turbo P-body harness in my glht to go smec. It took a little time to match everything up, but it wasn't that difficult. I would say it took me about 12 hours to make the new harness when all was said and done.

You basically cut the P-body harness bundle of wires on the engine side of the big rubber plug that goes through the firewall and from there you can either splice and solder onto the correct wires of the L-body bulkhead, or you can get really fancy and buy the correct pins/spades for the L-body engine side bulkhead and put those on your cut P-body wires and plug them right into the L-body bulkhead. The only other thing I messed with was the headlight plugs and blinker lights. I pulled the wires out of the P-body plugs and put them into the L-body plugs and since the P-body has an extra set of blinker lights, I just tucked those in right behind the L-body blinker so you couldn't really tell there was an extra set of blinker lights blinking (you have to leave the bulbs in them or your blinkers won't work).

Jon

[Pandemoniac]

Thanks for the info. The guy told me since I posted this he only wants the wires forward of the firewall, so at his request I'll hack off the harness right at the firewall. Looks like he's going to try his hand at splicing all the SMEC wiring into the l-body harness.
I'm sure he can do it... I'll soon be using a chevy truck ECU and harness in my 5.3 liter v8 RX7, that will probably be the harder job!

I pulled the wires out of the P-body plugs and put them into the L-body plugs and since the P-body has an extra set of blinker lights, I just tucked those in right behind the L-body blinker so you couldn't really tell there was an extra set of blinker lights blinking (you have to leave the bulbs in them or your blinkers won't work).

Couldn't one measure the resistance of the extra bulbs and wire a resistor in their place to keep the blinkers operating properly?

[jonnyb]

Couldn't one measure the resistance of the extra bulbs and wire a resistor in their place to keep the blinkers operating properly?

Sure you could do that, but leaving the bulb in there and tucking it into the fender behind the headlight bucket requires zero work...and I'm all about whatever is easiest...LOL!

[moparman76_69]

Get the diagrams from both and solder away. Just got done doing a j-body harness to 40-pin l body. Not sure if I'd do a p-body though it has all those little plugs instead of a bulkhead. There will be extra wires and confusion involved but it's doable.