geolab

I was riddled by the socket picture you had so I had time over the weekend and took a picture of the socket I have, only to find it is the same.
Now I have to investigate the porsche cable with an ohmmeter just checking continuity between the reader side plug, and the OBD plug. I am practically sure it is what I wrote above, but there is a chance I have reversed the pin numbers. Will let you know. regards

Lorenfb

:I thought the round 19 pin connector was found in the early 993s as well. I think the changeover to the OBD II connector was sometime during the '95 model year."

That's correct.

The OBDII pins on '96 993 and later;

4,5 - grounds
15 - 'L' line
7 - 'K' line (bi-directional)
16 - #30 (constant 12 volts)
1 - #15 (key 'on' 12 volts)

The 'K' & 'L' lines are used to access the DME, Air Bag, ABS, CCU, & Alarm unit.
You can always determine the pin orientation by finding pin 16 which is always
'hot' with the key 'off', i.e. the only 'hot'.

IXLR8

You mean the OBD II connector on the late 1995 993 with the "OBD I Certified" system as listed in the pic below.

1996 and later models have an OBD II connector with an OBD II system.

IXLR8

Since there are wires (and voltages present) at pins 3, 9 and 13, what does Porsche use them for?

Here is a chart I put together based on the 1995/2 wiring diagram out of the Porsche Repair Manual...

ToreB

Good work, this chart is handy.
Pin 7 is K line, this is the bidirectional serial port to the Motronic engine control unit.
Pin 3 is K' line, (K-"marked") this is the bidirectional serial port to the CCU, SRS, (airbag) ABS and Alarm control units.
Cheers,
Tore

IXLR8

Tore, do you know what "TN Signal" stands for at Pin 9?

ToreB

I don't know, but I'm sure this information is somewhere here on Rennlist. I see in the 993 schematics that the TN line is coming from the Motronic engine control.
Cheers,
Tore

Lorenfb

The TN signal is the engine RPM.

IXLR8

If that is for engine RPM, any idea what the "Speed Signal" at Pin 13 is and what it is used for?

Lorenfb

"any idea what the "Speed Signal" at Pin 13 is and what it is used for?"

Just like it says - "Speed", i.e. speedometer.