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OBDI -> OBDII


19Cutlass94

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Is there anyone that can convert an OBDI harness to an OBDII harness? Whats all involved in doing this?! If its not that bad I can take a shot at it, however if theres someone that knows exactly what they are doing, maybe Ill just have it sent out.

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I need to fiugure out the same thing. But I will probably just start by grabbing these from a donor:

 

96 wiring harness

97 pcm (obd II with more memory than the 96, but does not need the tank pressure sensor)

linear egr

maf sensor

maybe the three way temp sensor(or modify the 96 wiring to use the 95 sensors)

second O2 sensor or a fake one(how do you fake an o2?)

something related to the evap system which I don't yet understand, but it seems the dohicky changed.

Knock sensor!

 

 

 

Thanks Brian P (aka Betty) for the info above!

 

infact if anyone finds how to links please post them!!!

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I bought one of those simulators, swapped between the Camaro and Olds when I felt like it. I think the older ones had problems, but the newer one with the round ass end is good.

 

Oh and YES to DHP Powertuner for '96-97

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yeah I know about the DHP, but the most important thing here ( for me anyways ) is, is it possible to convert a '94 wiring harness to a '96 wiring harness?

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it's a lot of work. The PCM connectors are completely different, and you'll have to run new wiring for the MAF, secondary EVAP purge solenoid (ehk), change the wiring for the EGR, downstream O2, and a couple wires thru the firewall to the diagnostic port. There may be additional wiring needed since the injector harness plug is also different but I never checked why. I just swapped the underhood harness cause I found it easier to change a couple wires on the firewall connector and change a couple of sensors than change 50+ wires at the PCM.

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yes, I keep reminding myself to do this. The reality is I wrote it down and it's somewhere mixed in with a bunch of papers. One thing I do remember is the need to splice a 2nd thick power wire, so it goes thru 2 pinouts (like 95) instead of one (96+) Note that GM changed a lot more than just going to OBD2. They changed the much of the power distribution.

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how much different would it be to change a 90 OBD 1 to OBD 2?

 

I was debating on whether it would be possible to change my 90 TGP to OBD 2 and drop in a 4T65-E HD Transmission and make some power without worrying about burning up trannies. I've changed everything else on this car, why not the wiring harness?

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  • 11 months later...

yes, I keep reminding myself to do this. The reality is I wrote it down and it's somewhere mixed in with a bunch of papers. One thing I do remember is the need to splice a 2nd thick power wire, so it goes thru 2 pinouts (like 95) instead of one (96+) Note that GM changed a lot more than just going to OBD2. They changed the much of the power distribution.

 

Bringing this back from the dead!

Did you ever post the wires that needed to be changed? I am looking to do a OBDII conversion on my 95 GTP. All I need do do is swap a few wires at the firewall to make the OBDII wire harness work with the OBD1.5? Any other sensors that are different in the engine bay? I know the knock sensors are. And I already have the 96 top end swap done and the newer EGR is waiting to be plugged in.

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Ok from what I gathered via my notes I made the following changes. NOTE: RESEARCH THIS BEFORE ATTEMPTING. A GM SERVICE MANUAL IS PRICELESS FOR THIS KIND OF WORK.

 

On the engine side harness:

Pin K1: Splice this wire and add to location L1. Find a spare pin + short length of wire to do this. This is a heavy gage wire so make a good connection.

 

Move pin E1 to A3

 

A1 no longer gets used so this is a freebie 12V wire. I think the reason why I didn't just use this for L1 was because this is a thin 18 gage wire, not thick.

 

Pin J2 is the second diag wire, this needs to go thru the firewall to the OBD2 port. I ran this along the existing harness going to the drivers side, thru a grommet. You may be able to run this thru the pass side but I couldn't see shit behind the dash.

 

 

Any other changes in the wiring did not matter for operation *for my car* going from a '95 Cutlass base to a '96 Lumina LS harness.

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look up redzmonte's post(s) on 60* about OBDII in his 95 monte or PM him on there. i helped' date=' but i don't know have the info in front of me.

[/quote']

 

I PMed him on 60degreev6. How would you go about reading the PCM for codes then if you don't switch out the interior harness? From my understanding the I will still have the ALDL connector and not the OBDII.

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You just have to grab an OBD2 port and wire it up. Take it from the same car you get the harness from if you want. Two wires need to be added. One is that extra diagnostic wire, the other is a 12V constant feed. Ground, diag wire #2 are re-used from the OBD1 port.

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You just have to grab an OBD2 port and wire it up. Take it from the same car you get the harness from if you want. Two wires need to be added. One is that extra diagnostic wire, the other is a 12V constant feed. Ground, diag wire #2 are re-used from the OBD1 port.

yep.

 

 

iirc, for the outside harness, you have to swap both underhood harness, add a wire and swap another wire. you also have to change some wires on the tranny connector. there may be other things, but I can't remember for sure.

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