Porsche Enthusiasts Club Forum

After fiddling around with my 944S, and finding a few minor 'issues', but no major faults I still have a poor cold idle. It is fine once even remotely warm, and very good once up to temp, apart from some minor hunting.

I have checked most parts of the system that I could see affecting the idle, only thing left to replace are the plugs (within service mileage but looking dirty) and HT leads.

I have read a few times now that people have chased idle issues on the S or S2, and also 964's it seems, and finding that the only thing that put the idle right was to run a 'System Adaptation' using the Bosch Hammer. Seems it could be worth my while giving it a go if I can find a Hammer, or a modern equivalent.

Does anyone know of any modern scan tools that will do the same function on a 944S? A friend of mine has a PIWIS and a lead that will connect to my DME, but he hasn't ever tried connecting up to a 944 before.

Just to answer my own question, but at least it might help others, it looks like PIWIS (via a Bosch KTS520 iirc) will work OK on the older cars (944, 968, 928, 964, etc) - certainly system adaption is listed within the software menu for a 944 S - which is what I wanted to use.

Unfortunately my friend only had the OBD2 to 19 pin round diagnoistic lead, but the 944S and 87/88 928 use a 12 way rectangular connector.

When I looked at the connector (just next to ECU) on my car there was a male version of the plug being used as a blank with four pins, guess this is standard to keep debri out of the socket.

So I will making a lead up from 12 way connector to OBD2, then will hook up to confirm it works OK. Just need confirmation on my pin out which I'm hoping John at JDS Porsche will confirm as he made his own version of the Bosch Hammer and supplies both types of disagnostic lead.

Unless anyone on here can confirm the pin out?

I have the following pinout from looking at the OBD2 pin configuration and cross referencing with posts on Rennlist regarding the 928 12 way diagnostic connector - I don't have the wiring diagrams to hand to double check:

OBD2------------12 way diag

4&5 ------------ 2 (GND)
3&7 ------------ 10 (K line)
9 --------------- 3 (TD (RPM))
11 -------------- 4 (Knock)
15 -------------- 12 (L line)
16 -------------- 5 (and possibly pin 1) +12V

Whilst searching on the net I have struggled to find a supplier for these 12 way plugs (looks to be made by a company called KL part no. 9672/1), but if any other 87/88 928 or 944 S owners were interested I might look into getting some of these plugs made to be able to make up more diagnostic cables.

JDS could supply me the parts to make a lead, but it was quite pricey so decided I would try making one, before finding one in the car anyway, lol!

Trying to answer my own questions again I have found the '88 944 S wiring diagram online and have traced as follows:

12 way diag ------------ DME

2 ----------------------- C50 GND
10 ----------------------- 55 K Line
3 ------------------------ 6 TD/RPM
4 ------------------------- 21 Knock
12 ------------------------ 13 L Line
5 ------------------------- 18 +12V

Looks like I shouldn't link pin 5 & 1 on the diagnostic connector, even though I had read they are both 12v supplies I can't be sure where pin 1 is fed from looking at the drawings - need to have a better look. As long as I have +12v with ignition on pin 5 then that will be OK.

Found this image of the 944 S DME connector and seems to tie up with what I put up in previous post, so looks like my connections will be correct:



Just waiting for my OBD2 extension cable to come through then I will try it out.

Reading this with interest Hallsy.

I could do with something similar for both a 944, and a 968 which I think is a round 19 pin.

Good work!

I am off work at the moment with the tail end of the after effects of my illness of last year, but I might be able to help you out.. Somewhere at work, I have a lead which was for adapting the 1989-1996 round diagnostic connector on the end of a PST2 to a square 1988 12 pin connector, which came with the original factory PST2's,

If it is just a couple of pins you want probing, I am sure I might be able to get one of the guys at the workshop to dig it out and test pin to pin to see if your theories are right before you go blowing something up.

Off topic Jon, but not worth starting a new thread for: are you certain that the M44/52 differences were routine upgrade like the water pump and the cambelt adjuster?

I seem to have become embroiled in an internet argument with an insufferable know-it-all and a number of other recent 944 owners have joined in, all quoting the same spurious 944 fan pages which they regard as unquestionable references. These, you wont be surprised to hear, all suggest that the M44/52 was a 250PS engine.

Back on topic.....

Jon - hope you feel better soon and thanks for replying.

I am 95% the wiring is fine, but not sure which 12v feed (doubt it matters, a case of whichever is live with ignition I guess) should be used, either pin 1 or 5 on the 12 way diagnostic.

I have access to a obd2 to 19 pin round cable to bell out, so if you or one of your guys would be able to bell out the 19 way round to 12 way rectangular lead you have that would be a great help!!

John at JDS can supply both leads and I did ask him if he would mind confirming my proposed cable pinout but he has not got back to me

Jon, did you ever get chance to bell your diagnostic lead out?

My S is still stumbling at idle, smells like it's running rich, and has a distinct stutter at 2250rpm - I have checked the basics with a meter, etc and not found anything obvious, so would like to try a fault code scan and system adaptation.

I am pretty confident that I have the pin out correct, but would be nice if I could confirm it against a known cable.

Well I have now knocked up the diagnostic lead....

944 Work Pics by Hallsy01, on Flickr

I have only quickly plugged it into my OBDII tool, just to check at least the power connections are OK, it doesn't have the correct protocols in Torque to be able to talk to it....

944 Work Pics by Hallsy01, on Flickr

For anyone not sure, the 16V diagnostic socket is in the passenger footwell, underneath the carpet, just above the ECU...

944 Work Pics by Hallsy01, on Flickr

I now need to pop over to my friends garage to use his Bosch interface and PIWIS software, hopefully it will work OK - won't get chance until after Le Mans now, but fingers crossed I have got my connections right!!

Had chance to test the lead out today with a Bosch KTS520 interface and PIWIS software.

The software recognised the DME OK, and reported one unknown fault code, which was cleared OK.

However, there was no option for system adaptation under the 944 menu.

We went into the 964/993 menu as some 964's had the same ECU I believe, and sure enough we could now view engine sensor values, coding, etc. System adaptation was an option, but came up with an error when we tried, maybe because it was within a 964 menu rather than 944.

Was worth a try - seems that my lead works, but I would need a Bosch Hammer, or re-worked equivalent for the adaptation to work.

Car felt good today anyway, so probably not worth worrying about, lol!!

where about are you located, id like to try plugging my snap on scanner. it has got software for later cars. maybe it will work on yours too

Hi Brewer, I am in Suffolk - but I can post you my lead if you want to try it?

Did the S2 use the 16 pin diagnostic port as well? I think the S2 uses the Bosch M2.1 DME, same as the S, but not sure whether they use the same dianostic port.

I'm not sure whether a snap on tool will work with these DME's, but no harm in trying, it may well read fault codes, but doubt it will read sensor values or do a system adaptation. If you have any info on the scan tool, see if it can use the ISO 9141 protocol, as this is what the M2.1 uses from what I have read.

PIWIS would read the codes OK, and read sensor values via the 964/993 menu, but system adaptation would not work. From reading around a bit, even though they use the same DME, the memory areas are possibly assigned differently, so that is possibly the reason for the adaptation not working.

If you'd like to try my lead, let me know your address and I'll post it out.

Had a look in a car, i got round connector and some random square, but its only 8 pin. Shame
Ill ask my local snap on dealer next week what protocols its able to communicate.
Thanks for the offer anyway