OBD1 to OBD2

[Atl_Monte]

working on an LT1 project for another one of my cars and its been suggested over and over that I look into going with an OBD2 ECM, its a 95 LT1 engine and wiring harness but I don't have the ECM(which would have been OBD1) what all would I have to do to use a OBD2 ECM with this engine and harness?

[TraceZ]

Why would you want to do that?

It's more common for people to go the other direction.

[Rob B (shoebox)]

OBD-II provides a few things you don't currently have:
rear O2s
crank position sensor
EVAP vacuum switch

These things would have to be programmed out, unless you swap harnesses and add the components (a lot of work/expense for nothing, IMO).

The biggest reason for switching I to II that I have heard of is to get rid of a no shift condition with a high stall converter. Tuners have now figured out how to make that work with OBD-I. OBD-II tuning is generally more expensive, too. Not much reason to switch, IMO.

[fastTa]

You won't have to modify the harness at all. The OBD-II PCM will plug right in. However, you will need to switch to a OBD-II knock sensor. OBD-II PCM's have a knock sensor circuit with right around 100k ohm inline resistance. OBD-I is a much lower resistance at 4.4k ohms. OBD-II also has the ability to "hear" more sensitively in regards to vibration frequency. This can be a good and bad thing depending on whether the knock is real or not.

There used to be a significant problem with people running anything over a 3000 stall on a OBD-I car. Most tuners, like Rob mentioned, have discovered a way around that.

Generally speaking the majority of people use OBD-I just to save a buck on tuning and it is a little less involved in the way of tuning for emissions.

In my opinion though, if this is going to be mainly a street/strip car and if you want the ability to do a little more in depth tuning, and take advantage of the misfire detection provided by the CKP(crank position) sensor, I would also go with OBD-II. Misfire detection is a very useful tool. That alone is worth it in my opinion.

[Atl_Monte]

The engine is a 95, so I'm not sure if it has a crank sensor

[Rob B (shoebox)]

The engine is a 95, so I'm not sure if it has a crank sensor

A stock 1995 f-body does not have a separate crank position sensor.
(oh, yeah, I already said that)

[Atl_Monte]

A stock 1995 f-body does not have a separate crank position sensor.
(oh, yeah, I already said that)

so it would just be easier to get an OBD1 ECM?

[fastTa]

so it would just be easier to get an OBD1 ECM?

It should already have a OBD-I PCM.

[Rob B (shoebox)]

so it would just be easier to get an OBD1 ECM?

I think so. (it's a PCM, not ECM)