jj99c2

I am connecting a G2X to a 1999 996 and want to set up the RPM signal. Searching the boards it sounds like a standard tach signal is routed to the OBD connector. I haven't been able to find out which pin of the connector it is on -- anyone have that information?

If there is a source to purchase the connector that would be great as well so I can wire up a harness.

bobt993

You should be able to get this right off of the instrument gauge and get a solid duty cycle pulse. My 993 is connected at the tach this way. Check the forum site on G2X extreme for the 996 hookup.

cchan

I've been working on this too (today as a matter of fact!), but I'm connecting a G2X to a 2004 GT3. The RPM signal is on one of the "unused" OBD2 port pins, but what I've been told is that the pin may vary for different 996 models/years/DME versions.

I have yet to verify that it works, but I've been told to use pin #9 on my 04 GT3. I've also seen references to a green/purple wire - which matches pin 9 on my car. Since your car is older, it might be different - but hopefully this info will help.

As for OBD2 connectors, I am building a cable using plugs from Peake Research (no affiliation). They actually have a lower profile right-angle adapter that's not shown. It's pretty easy to put together as long as you can do basic soldering. It fits nice and snug too. I'm sure there are other sources too. There were some pre-wired cables, but the basic ones may only be wired for the 4-5 normally used pins. This company was just close to me. Downside is that their minimum order is 5 plugs. (now I've got a few extra I sell to friends)

Good luck!

Ed Newman

Give me till next week and I will have tested hookups for RPM, Brake, Throttle Position and A/F mixture.

jj99c2

Thanks for all the information!

cchan - I will check and see if pin #9 matches green/purple wire. Link for OBD2 looks good as well. Do you have pins for power and ground mapped out?

Ed - looking forward to your results.

cchan

pin 4 should be battery ground, pin 5 "signal" ground, but I think it's tied to pin 4 anyway (I did a continuity check), so either should do for ground. The little circuit board on the OBD connector I have ties them together anyway.

pin 16 is +12V... but personally I'm not inclined to use it on the thought that the OBD port wasn't designed to really power anything and am concerned about pulling too much current through there. Plus given that OBD plugs typically aren't the most reliable connector, I'd feel safer using another power source.

For now, I'm just using the cig lighter for power, although I eventually want to tap into the cell phone connector in the center console. I would prefer to find the right sized pins to fit the AMP or Molex connector rather then cut into the wire, but haven't had much luck finding them. The holes are bigger than the standard Molex 0.093" pins.

cchan

RPMs on pin 9 worked for me, I got it all set up just in time for a DE this past weekend.

Regarding powering the system, I now think the easiest is just using a cigarette lighter plug to power the system. It's easy enough to plug it is while seated in the car at the beginning of a session, versus trying to put an on/off switch somewhere convenient and reachable once belted in. I found Radio Shack even makes a cig lighter plug with a switch built into the plug, so I'm going to use that to make my own power cable to reach the G2X and also splice in the RPM signal wire.

Where are you guys mounting the unit? I came up with a pretty hack solution to the rear end of my GT3's center console in between where the rear seats would be... photos attached.

jj99c2

I finally got the unit installed in the car and can confirm the green/purple wire on the OBD port does provide the tach signal on a 1999 C2 as well. I ended up pulling power off of the cell phone connector in the center console.

Thanks for all the help. Looking forward to trying it out this week!

cbracer

Here's a link with some information:

http://www.cb-racing.com/boxster_OBDii.html

karlooz

i think you would want a better signal than the OBD2 port. it only has ~5Hz cycle... kinda slow. my MXL pista. if you have a 2000+ 996 then you can interface with the CAN bus. unfortunately mine's a '99 so i have to tap into the instrument cluster tach. much better signal ~200Hz.