THE OBD1.5 to OBD1 Conversion Thread

[robertisaar]

Yeah I was going to ask if the new PCM is bigger/smaller than the OBD1.5 one?

What wire did you have to mess with for the 5v reference for MAP/TPS? I take it if we use your guide we will be fine.

the 1.5 is about 1/2 inch wider, 3/4 inch taller, and maybe 3/8 inch longer(looking from the top with the plugs facing towards you)

and i really don't remember what i did, but its in the guide...

[IsaacHayes]

Yeah I was going to ask if the new PCM is bigger/smaller than the OBD1.5 one?

What wire did you have to mess with for the 5v reference for MAP/TPS? I take it if we use your guide we will be fine.

EDIT: Maybe you could do a core for the 1.5 ECMs? That would work if when the user got the adapter that a preloaded tune was on there that would run their car OK if it was their DD. I wonder how the trans shifting tables will work with your trans, as it might cause issues if it does go by MPH with the different FDR of the 3100 4t60-E's compared to LQ1's. Mine is 2.94 and the LQ1 is way higher ratio than that.

[robertisaar]

we'll see about drivability... i already have a tune set up for it, but i do want to see how the stock chip reacts to determine wether or not a custom chip is necessary for this swap to be done without it.

there are a few useful things there, but it would be cheaper to get them through GMpartsdirect. it would be nice to find a retailer with the 1.5 PCM plugs. PSG takes too long for that.

EDIT: yes, the simplicity of OBD1 does lend itself to be modified easily and allows a pretty wide range of stuff to be installed.

[IsaacHayes]

http://www.eficonnection.com I wonder if they have anything you could use? I haven't looked, probably not though. They did have some MAP connectors that I could of made an adapter for my 3500 MAP, but I'm not going back to the old style for any reason so I just soldered and heatshrinked it on my old wires.

Your idea of making an adapter so you just plug into the stock harness, and into the new ECM is what I was going to do if I went to OBD2. That is unless I had the engine out and had access to a cheap engine bay harness. The junkyards here would make you pull it yourself and probably charge $300.

The adapter is great because if something isn't right you can just plug back in your old ECM and get back on the road. (great for people like me who mod their daily driver and can't have the car not work). That way you could tune on the weekend, and swap back to original ECM for the work week until you get the fuel/etc at a good driveable level without burning too much fuel or driveability problems.

You said the LQ1 tune though runs it pretty well huh? I wonder how well it will be once you start actually driving it though.........

EDIT: more comments
OBD1 is fine with me if the everything works. OBD2 is cool and all, but with DHP out of the game it's hard to sometimes find a used unit. And I don't like the HPT license scheme. I do like though if I got a DHP I could tune lots of GM vehicles (maybe a new DD?). But OBD1 lots of tools and support out there that's not going away. Heck maybe Ben can even get some tunes going for 3400 swaps for 4T60-E cars, etc.

[robertisaar]

and this is why you're supposed to measure twice and cut once...

but it works, so i don't care

so long as nobody asks me why i ripped a leg off of a giant tarantula and have it connected to my PCM, i don't care that it looks funny.

i also need to see if i can get the "new" pcm to lock into the retainer for the "old" one, or else i'm going to have to fab a bracket or go to the yard to try and get one...

[robertisaar]

i imagine a chip/harness adapter combo wouldn't be bad...

but yeah, i've got nothing better to do.

i'll see how far off the VE tables are soon.

[SappySE107]

I would certainly list them on the store if you want to supply them. I can probably help on the tuning end of things.

[robertisaar]

went to rockauto for some info and apparently these are all of the vehicles that came with the PCM, useful for anyone scouring the junkyards looking for a PCM to rip apart. i'm assuming these are all for the 3100 and RWD3.4 versions.

BUICK REGAL CUSTOM (1994 - 1995)
BUICK SKYLARK CUSTOM (1994 - 1995)
BUICK SKYLARK GRAN SPORT (1994 - 1995)
BUICK SKYLARK LIMITED (1994 - 1995)
CHEVROLET BERETTA (1994 - 1995)
CHEVROLET BERETTA Z26 (1994 - 1995)
CHEVROLET CAMARO (1994 - 1995)
CHEVROLET CORSICA (1994 - 1995)
CHEVROLET LUMINA 1995
CHEVROLET LUMINA LS 1995
CHEVROLET MONTE CARLO LS 1995
OLDSMOBILE ACHIEVA S (1994 - 1995)
OLDSMOBILE ACHIEVA SC 1994
OLDSMOBILE ACHIEVA SL (1994 - 1995)
OLDSMOBILE CUTLASS SUPREME (1994 - 1995)
OLDSMOBILE CUTLASS SUPREME S 1994
OLDSMOBILE CUTLASS SUPREME SL 1995
PONTIAC FIREBIRD (1994 - 1995)
PONTIAC GRAND AM GT (1994 - 1995)
PONTIAC GRAND AM SE (1994 - 1995)
PONTIAC GRAND PRIX SE (1994 - 1995)

[robertisaar]

all I got to say is....if you do decide to build and sell a few of these things, I get the next one! I was honestly just going to pop pins and swap plugs, but the idea of an "adapter" plug....love it! If I ever go south and find a 2-door of my car with perfect body...it'll save me a ton of work I'd rather not do twice.
Besides, you went through the trouble, get something for it!

that was the idea of the adapter: should something happen to the original car, the adapter will probably survive and be able to transferred to another vehicle.

and i'll build them for people, but i don't know how much people would want/are willing to pay for them... name a price and i'll see what i can do.

EDIT: on a slightly related note: Ben, would you be willing to list them at WOT-Tech if i build them, and the store/site gets a cut of the profit?

[95SleeperAcheiva]

all I got to say is....if you do decide to build and sell a few of these things, I get the next one! I was honestly just going to pop pins and swap plugs, but the idea of an "adapter" plug....love it! If I ever go south and find a 2-door of my car with perfect body...it'll save me a ton of work I'd rather not do twice.
Besides, you went through the trouble, get something for it!

[robertisaar]

rob, if this works out... how much you going to sell them for? I'm almost willing to buy one now even without you testing it!

you got me thinking...
so i went to gmpartsdirect.com and found out the current cost for everything... its 77.82 for everything (without shipping) except for the internal PCM plugs(because they don't have them, and the only place i can think of for obtaining them is power and signal group, but that requires setting up a business account and ordering samples...not too bad of a route, but the cheapest, fastest and easiest way would be to bust open the PCM you have and desolder the plugs that are attched to the board and use those...

and the silicone seals should you choose to use them would be an extra 9.33

i imagine you could also get most if not all of the parts through a dealer, but i don't know what they would charge...

[robertisaar]

here's the PDF. i think i have all the grammar and spelling correct, but we'll see.

EDIT: guide has been moved to page 1 for not needing to scrounge through the thread.

[robertisaar]

It was the 5 volt reference that goes to the MAP and TPS. I don't know what the fix would have been but I know that is what the issue was for Brad when he was here.

and whatever i did seemed to fix it.

and you'll probably think i'm full of shit, but i think it came to me in a dream... because i remember waking up, looking at the wire diagram and knowing exactly what needed changed...odd.

[robertisaar]

Having damage on the car is #1 reason for attention. Trust me after I hit a deer cops were busting U-turns and following me at all times of the day. Not just at night.

Have you ordered the stuff to burn chips yet?

i've had it for a few months, been trying to get wifey's 90gp tuned, but its proving to be troublesome... i think its the $88 definition. i'll have to convert it to $A1 one of these days... that or the o2 sensor is that bad. but it used to have really bad KR, and i've slowly gotten that to 0. fuel economy/idle quality have improved as well.

[IsaacHayes]

Having damage on the car is #1 reason for attention. Trust me after I hit a deer cops were busting U-turns and following me at all times of the day. Not just at night.

Have you ordered the stuff to burn chips yet?