1995 Pontiac Bonnie with OBD II , can't get a read

[mhobryan]

It has the OBD II scanner connector, but I've tried 4 or 5 different scanners, and all i get is a link error. As OBD II started in 1996 do i need a 'special' scanner or software to read, or is there an issue with my connector/link that I need to troubleshoot?

No codes now but it does make diagnosing more challenging.

[00Beast]

Yes, 95 had "OBD 1.5" which requires an OBD 2 plug on an OBD 1 scanner. Several members have purchased/made these cables, I'm not an expert on them by any means...

[sandrock]

There is only 1 scanner that can read OBD1.5, can't think of it but it's a Actron, a big black box and VERY hard to come by nowadays.

And FYI...OBD1.5 isn't close to OBD1. It's pretty proprietary to GM believe it or not...it uses OBD2 interface socket but doesn't use OBD2 pinout nor does it use OBD1 protocol. The only thing in common to OBD1 are the codes that are output. Both Don and myself found out a great deal of information on this subject when:

1) I converted my '93 SSEi to run a '97 OBDII PCM
2) I converted Dons '95 TranSport to run OBDII for his L26 conversion
3) I converted Dons '95 Bonneville to run OBDII so he could be rid of the troublesome 94/95 PCM that had already gone through 4 computers and none of them were really worth a *dang* to start with.

[MattStrike]

I thought that the protocol was the same as the OBD-1, only the connector and request ID changed, even most of the parameters are in the same spot in the message? We were using a '94 Regal and a '94 PA, the Regal was OBD 1 and the PA was OBD1.5 so they may have changed OBD1.5 for '95 or I'm forgetting something, but all we had to do was change the OBD1 connector to the OBD1.5 connector and we got most of the data.

Now I'm going to look at the datastream sheets I have...

Easy way now is to make/buy a cable (set) and use pc-based software. There are several options.

[mhobryan]

3) I converted Dons '95 Bonneville to run OBDII so he could be rid of the troublesome 94/95 PCM that had already gone through 4 computers and none of them were really worth a *dang* to start with.

Is there a write up on this? What years/makes/models could i use as a donor for parts?

[MattStrike]

More importantly, was there a performance/mpg benefit?

[sandrock]

When Don and I did it, it was primarily to get rid of the PCM he had, as we both knew that you can't get those PCMs new anymore, and even the remann'd units were shoddy at best. They weren't that great even when they were new.

From the standpoint of reliability...the conversion works. When I did the conversion on my '93, I chose the '97 PCM because I already had one. When I did the other two swaps, I already had the '97 Bonneville lineup unlocked through HPT, so I had unlimited tuning. I had done a 4th PCM swap...'97 Bonneville to '03 Grand Prix PCM, but that's another story.

From reliability to processing speed, the '97 PCM beats the 94/95 hands down. But there's a reason why Don and I haven't posted any how-tos on it...for starters, it isn't for the faint of heart. Cutting, splicing, soldering, heat shrinking, running new wiring, deleting old wiring, part swapping...it's not a weekend plug-and-play deal. First conversion took about 6 months, second conversion took a month, the third took several weekends. The more I did it, the more I knew what directions to go. Each project was different too.

Now, for the performance aspect...the performance lies in the tuning. That's all I can say about that.

If anyone wants to follow in our footsteps, we'd be more than happy to help via PM. But due to the issues I mentioned above, you have to have a good working knowledge of electronics and swaptronics to successfully complete the task, and it's info that we'd rather not have out in the public due to...liability.

[sandrock]

This was the first swap I had done, after some initial tuning. I used a '97 L67 file, which I had to modify a bit to run the 4T60e. This was far from fine tuned, and unfortunately the engine let go soon after the conversion (no fault of the conversion mind you, it was a whole 'nother thing), but this was running WAY better off of this pcm than the original '93 computer.

[sandrock]

I thought that the protocol was the same as the OBD-1, only the connector and request ID changed, even most of the parameters are in the same spot in the message? We were using a '94 Regal and a '94 PA, the Regal was OBD 1 and the PA was OBD1.5 so they may have changed OBD1.5 for '95 or I'm forgetting something, but all we had to do was change the OBD1 connector to the OBD1.5 connector and we got most of the data.

Now I'm going to look at the datastream sheets I have...

Easy way now is to make/buy a cable (set) and use pc-based software. There are several options.

Wanna know something interesting? The PCMs were interchangeable between models...even the '95 TranSport used the same PCM as the '95 Bonneville. But the PROMs were much different. The PROMs contained more than just the operating tables, they contained the whole instruction set on how the PCM operates, right down to what pins were active and which ones weren't, and how those pins were assigned. So programming the PROM for the Regal to be OBD1 and the PROM for the PA to be OBD1.5 isn't surprising or far-fetched. OBD2 was a mandate for the 1996 model year for ALL makes and models, so the years prior were used for transition and real-world testing. Chrysler had their OBD2 ready for '95, even for their outgoing K-based models AND their new Neon. Ford...not too sure about, never got into them at that time. GM was playing catch-up.