Cloud9...68

I'm in the home stretch of installing an Aim data acquisition system (EVO4S/GS Dash/SmartyCam HD, with analog sensors for throttle position, brake pressure, and steering angle) in my track-focused 92 968. The last major step is tapping into a source for the rpm signal that I need to connect to the patch cable for the EVO4S unit. The rpm signal can be obtained from the DME, either by tapping into the appropriate wire from the DME connector, or at the tach. The other option is from the coil, which sounds like the less desirable option, so I would prefer to get the signal from the DME.

According to the description of the DME pins in the manual, I need the wire coming from Pin 6. However, I can't find a wiring diagram for the DME in the manual, so I have no idea which of the 48 wires coming from the DME is the one going to Pin 6. As far as tapping into the wire at the tach, that is an option, but I remember that removing the instrument cluster on this car is a fairly delicate and difficult operation, and not without risk of breaking something on the way in or out, plus I won't know for certain which wire I need to tap into. So, I'm kind of stuck, and was wondering if anyone here has ever done this before, or if anyone has a copy of the wiring diagram for the DME. Thanks.

refresh951

Cloud9...68

Thanks - where did you find that? Unfortunately, the DME for a 944 Turbo turns out to be very different from a 968 - the 968 has close to 20 more connectors! Would you by chance be able to find the same diagram for a 968's DME, or show me where to find it? Thanks.

V2Rocket

https://www.porscherepair.us/porsche...unit-plug.html


Note

Slots marked black are not used.

1 Ignition coil

2 Ground, ignition output stage (MP IX)

3 Ground (Fuel pump relay)

4 Idle speed positioner, opening winding

5 not used

6 Speed signal at rev counter

7 Air mass sensor signal

8 Hall sender signal

9 Speed signal from speedometer

10 Ground, electronics (MP VIII)

11 Knock sensor 1

12 Positive terminal, Hall sender / throttle

13 Diagnostics L-wire

14 Ground, injection valves (MP IX)

15 not used

16 Injection valve cylinder 3

17 Injection valve cylinder 1

18 Terminal 30

19 Ground, electronics

20 not used

21 Check Engine warning lamp

22 Idle speed positioner, closing winding

23 VarioCam

24 Ground of remaining output stages (MP IX)

25 Hot-wire burnoff

26 Ground, air mass sensor

27 Terminal 15

28 Oxygen sensor/idle CO potentiometer

29 Knock sensor 2

30 Ground NTC/shield knock sensor

31 Knock yes/no

32 Control of AC relay

DME-Dlagnosls/Troubleshootlng

Printed in Germany - III, 1991

Cloud9...68

V2,

Yes, I have all that - I have a manual. What I'm looking for is the ability to identify the wire coming from Pin 6, so I can tap into it with the patch cable for my EVO4S data acquisition signal processing unit. In other words, I need exactly what refresh951 found, except for a 968 rather than for a 951. Yes, I realize this is the 944 Turbo forum, but there tends to be a lot more technical knowledge on this forum than on the 968 forum.

V2Rocket

doesnt the back cover of the DME plug slide off when you remove the small screw at the end? then just locate the pin#6 on the front side and trace the wire.

Cloud9...68

Not in any way that I can tell. I tried removing the screw, but can't see a way to to pry the pack cover off of the DME plug. You would think it should come off, but I'm not seeing how. But even if I was able to identify the wire, it would be messy, to say the least, to separate it from the other 47 wires in the harness, tap it, and put the harness sheath back on. Tapping in at the coil is sounding better and better all the time...

Raceboy

On 968 55pin DME connector, pin 6 is rpm signal to tach. It is 0.5 mm2 red/blue wire.
Before tapping the signal I strongly suggest to verify thet you tap correct wire because in the DME connector there are several re/bl wires though they are different thickness (thicker ones).

Cloud9...68

Raceboy,

Thanks - that's the information I was looking for, although I agree it doesn't sound straightforward to unambiguously identify that wire within the bundle coming from the DME connector, even knowing its color. However, it should make it easy to identify the correct wire to tap going into the tach. I'll take a look under the dash when I get home from work (yes, I'm working on Labor Day) to see if I can spot a red/blue wire in the vicinity of the tach. Working under the dash of this car is no fun, though, especially with a fixed-back racing seat that's bolted in place, and I'm not sure how easy it's going to be to maneuver my way to reach and tap this wire. The rpm signal isn't all that critical to me - if getting to the correct wire under the dash looks like too much of a pain, or if it looks like I have to remove the gauge cluster to get to it, I may just go ahead and connect the appropriate wire on the patch cable at the coil.

968workaholic

It needs to be a square wave signal for the AIM, using the coil trigger wire will not work on these cars, I have tried. Use the wire at the smaller DME wiring harness plug that connects to the body harness,. Pin #2, green with a black tracer on the 14 pin plug

968workaholic

Cloud9...68

968workaholic,

Thanks very much - you saved me from wasting a bunch of time, not to mention the physical pain of working under the instrument cluster! I'm at work at the moment, so could you please tell me where the 14-pin plug you're referring to is located? I see from the wiring diagram you posted that it's somewhere in the passenger compartment, so it should be easy to find, but in case it's hidden somewhere, please let me know where to look. I'd love to get this part of the project wrapped up today, so I can start with the configuration of the system.
Thanks again.

968workaholic

Just follow the DME harness back from the computer and you will find it. Maybe 10-12 inches back from the computer plug is where the wires come out if I remember correctly

Cloud9...68

Thanks - that's what I thought, based on your earlier description. Just wanted to confirm before starting the search in case it was hiding in a different location than I expected.

By the way, how on earth did you figure out this was the correct wire to tap into?

968workaholic

Followed it back from the tach in the wiring diagram. I figured if the signal was good enough for the factory unit it should work for aftermarket pick-up. Why on earth you can't use the - on the coil still doesn't make sense, guess that's just the way it is.