Diagnostic ports on 1988 & later 944/968

[guru944]

How many of my fellow members know your car may have pre OBD1 diagnostics built in from 1988 and later Porsche Vehicles.
I have seen the 9268 adapter 12 pin port and 19 pin connector and later OBD 1/2 Ports on the 968/964 as well.

I already know of the 928 9268 12 pin (cabin)and 951 5 pin diagnostic port under the hood.

Sound off.
Later......

[guru944]

Well, I am looking to upgrade my 87 944S DME Motronic 2.1 to include diagnostic OBD1/2 with the J1914 Bus protocol for better tuning, troubleshooting and development (datalogging). I have seen on Rennlist online that some other 944/968 owners are using various OBD1/2 scanning tools Hand Held, Laptop or even wireless via smartphone. Since I already have 2 of those tools already listed, i will be hardwiring a OBD 2 Port into my harness for plug-n-play. Already have a later DME to bench test and finalize the intergration. Don't you just love upgrades?
Later...

[flash968]

so far, i know of nobody having been successful at getting an OBD2 device to work with the OBD1 electronics of the 968. a few have tried. yes, there are devices that can be connected to the OBD1 port and electronics. the bosh hammer works, as does the durametric. however, those both have a package specific to the model of car.

the software is not the same for both systems, and consequently the scanners and software for OBD2 do not work with OBD1, even if you get a plug in there. OBD2 is standardized, and is the same from one car to the next. OBD1 is not. consequently, unless the software you are using has a package for this specific car, it will not work.

[flash968]

if you do manage to get it working though, i would love to hear about it. we are about to supercharge another 968 engine, but this time in a 944, which has no port at all. i would love to be able to hook up the durametric to it.

[RedBaron]

Very interested in this for my S2!

[flash968]

yeah - would love to see this work out. unfortunately all attempts i've heard of thus far have resulted in the OBD2 devices not being able to talk to the OBD1 software/ECU. it's as if they were speaking a different language.

[DannoXYZ]

Not only is OBD1 protocol different than OBD2, there was actually no OBD1 "standard" at all. Each car with OBD1 will have a unique and specific protocol implemented by that manufacturer. A Toyota OBD1 scan-tool won't fit a Porsche OBD1 ECU. A BMW OBD1 tool won't fit on a SAAB, etc.

And if you were to somehow make an adapter to physically fit, there's issues of different baud-rates. Some are 300-baud, some are 100-baud, some are 102-baud. Sure, you can use a buffer-chip to gather all the data on one side and send it out the other at the right speed. But even then, the actual data sent across won't be compatible anyway.

[flash968]

yeah - i mentioned the lack of standardization a few posts up. as you say, that is just one of the problems. the cable is the least of the worries. heck, they sell one of those on ebay.

like i said, a few have tried. none that i know of have succeeded.

good luck

[kdjones2000]

And that stuff is only good for I think the 90 and up cars. The ones that require the "hammer" to reset the air bag light.

'88 and '89 944's are pre OBD-I.

[flash968]

actually, according to the workshop manual, 88 and up have a diagnostic port, but it's not a round 19pin connector, but rather a square 12 pin one. the hammer still works on that, as does the durametric, but you need an adaptor to go from 12 pin square to 19pin round (or individual wire plug-ins)

unfortunately, the car we are about to do is an 87

[guru944]

Update:

OBD1 (1989 Standard) is a Uart based data link OSI protocol uses ISO 9141 K and L line for signal communication.
OBD 2 (Late 1995) Is much more complicated as it supports ISO9141-2 and 4 others including Can Bus for 2003 and later Vehicles.
OBD 2 Scan or programming Devices may not fully support OBD 1 as the OSI layers are different within the protocol.

The 1987/88 944S and 928's have a diagnostic port 12 pin integrated within 1 meter of the DME. That became a standard in OBD 1 only two years later. Porsche is always ahead of the everyone else because of their Motorsports R & D involvement. Only 4 wires are really required to wake up dme for session. These DME's are adaptive and ML2.1 is used not only in the 964 but also in the 993 as well as ML2.1.1 is in the 968 with its MAF and sequential EFI
setup.
Finalizing the DME and bench setup with Fluke scope meter to Monitor and log com sessions and see raw data wave forms for synchronization.
I'm excited! waiting on a few more mini female pigtails to wire all the grounds on pins 10, 42, 14 and 19 at the 55 pin dme connector header.
later...

[RedBaron]

I assume this 12 pin diagnostic port is the rectangle plug near the DME?

As an aside, how did you get 250 HP from your S?

Originally Posted by guru944

Update:

OBD1 (1989 Standard) is a Uart based data link OSI protocol uses ISO 9141 K and L line for signal communication.
OBD 2 (Late 1995) Is much more complicated as it supports ISO9141-2 and 4 others including Can Bus for 2003 and later Vehicles.
OBD 2 Scan or programming Devices may not fully support OBD 1 as the OSI layers are different within the protocol.

The 1987/88 944S and 928's have a diagnostic port 12 pin integrated within 1 meter of the DME. That became a standard in OBD 1 only two years later. Porsche is always ahead of the everyone else because of their Motorsports R & D involvement. Only 4 wires are really required to wake up dme for session. These DME's are adaptive and ML2.1 is used not only in the 964 but also in the 993 as well as ML2.1.1 is in the 968 with its MAF and sequential EFI
setup.
Finalizing the DME and bench setup with Fluke scope meter to Monitor and log com sessions and see raw data wave forms for synchronization.
I'm excited! waiting on a few more mini female pigtails to wire all the grounds on pins 10, 42, 14 and 19 at the 55 pin dme connector header.
later...

[guru944]

Update:
Finally got all the wiring done on the DME. Testing should begin tomorrow.

Later...