how to add OBD plug to 3.6 transplant

[siverson]

Hi everyone,

I'm trying to hunt down a problem that's popped up on my 1991 964-powered 1974 914.

I completed my 3.6 conversion 5+ years ago, but never really had the need for an OBD plug until now. And it sounds like a fun project. So I'd like to add a diagnostic plug so that at the very least I can read and reset error codes - that's all I really need.

To do this, it looks like I really only need 4 pins from the ECU: K line, L line, power, ground. I've done some research and it seems like the factory 19-pin round Porsche plug on 964s is somewhat of a rare plug. It seems one company (JDS Porsche) might sell a reproduction, but I haven't heard from them yet.

My idea: Could I add a readily-available, female 16-pin OBD-II to my 964 wiring harness and use a more common adapter cable to read the OBD-I codes? For example, would this work: Porsche Diagnostic Store | Durametric Software Products for Sale

Does that make sense? Any ideas?

-Steve

[spuggy]

You seem quite handy, there might be some info here you can use Information on the Porsche 964 OBD Motronic interface

Pity you don't have the socket on the harness and need the plug, that's cheap: http://www.sensolutions.com/products/browse-products/manufacturer-specific/?tx_commerce_pi1[mDepth]=2&tx_commerce_pi1[path]=42,3

But it looks like the answer to the question is "yes", as there's a cable to connect the 19-pin socket to an ODB-II: http://www.sensolutions.com/products/browse-products/porsche/diagnostic-adaptor-for-porsche/

[Moses]

How to use an OBDII diagnostic port in a 3.6 transplant.

[siverson]

Moses, thanks - honestly, I searched! I'm not sure how I missed that...

[Moses]

Originally Posted by siverson

Moses, thanks - honestly, I searched! I'm not sure how I missed that...

Search is funny Searching OBD or OBD2 won't find it. I had to search myself. Found it with OBDII

[ischmitz]

It really doesn't matter what style connector you use to do this. I used a LEMO connector and made a cable that can interface to the Hammer (or adapter on the PST-2). This way any standard hammer or PST-2 can interface with my car.

For the Hammer or PST-2 to work you need +12V, GND, K-line, L-line. Then there are three special lines that are optional: the knock-count line (if you care about the knock count function), the CEL line (not sure if it is used at all), and the engine speed line (also don't think it is used). My hammer and my PST-2 works fine with just the K-line and L-line hooked up.

So in total you have to get 7 signals. Most of them (except GND) are found on the 16-pin connector on the DME harness close to the DME.

Ingo

[siverson]

> It really doesn't matter what style connector you use to do this. I used a LEMO connector and made a cable that can interface to the Hammer (or adapter on the PST-2). This way any standard hammer or PST-2 can interface with my car.

Right, makes sense to me. I just thought I'd use an OBD-II connector because (a) it's readiliy available compared to the proprietary Porsche 19-pin connector, and (b) it seems like it will make the car available to more scanners without needing an adapater. And since I can pick any arbitrary connector, why not.

> ... any standard hammer or PST-2 ...

These are still quite expensive, right? I've found a used Durametric cable (USB -> OBDII) + software I'm going to try on my car (only $200)...

-Steve