DME wiring diagram.

Hi There Does anyone have the wiring diagram to the actual DME (Motronic 7.8 ) unit. I have searched and searched to no avail. Pinouts I have, but I am looking to identify the various components. Many thanks! Berni

Just out of interest what are you hoping to do with this information? Your best bet would be buy a second hand DME and take it to an electronic engineer. Are you looking to replace a failed component?

May be buried in here somewhere, unless you have already pored over it. Happy digging. http://911uk.com/viewtopic.php?t=83491

Hello, Thank you, will have a hunt through that thread. Yes I'm trying to find out what components relate to the o2 sensors. I have a suspected pre cat (bank 1) fault in the ECU. So in the flavour of DIY I would like to fix it myself. Of course I could just but a new set (and I would at the right price if it had 2 remotes) or send it to ECU doctor, or indeed take it to Porsche. The car runs fine, but of course it is not optimal. EDIT: Sadly the diagram is not in that post......... Thanks again Berni

I'm afraid Porsche don't teach us the internals of control units .. they don't even explain the software to any degree .. it's just inputs and outputs and as such with nothing like this then there will be next to nothing data wise to find .. unless someone has back engineered one . I searched .. i found some of the earlier models .. probably the same as you but not what you are after . Transistors for injectors / coils are at each side but O2 sensor .. hmm .. that's going to be a chip i would have thought . Best way .. wiring diagram ... see which pin on the dme are the O2 and try and trace it on the circuit board .. ignore resistors etc .. find the end destination . If its a chip then it's unlikely you would be able to source parts or even replace it . My guess is even the ecu doctors can only fix the basic items .. a chip replacement is a wee bit difficult .

Hi deMort Thanks for trying and the input! I am probably wasting my time trying to hunt this one down. In fact I am really bad at anything electronic. I exploded an iPhone battery (scary) last year, and when I changed the battery on mine last week broke one of the two cables that go to the screen. My brother is better than me thankfully. I think the chips are standard EPROM types that would need to be programmed. In my mind I imagine that I can copy the code from the working o2 chip and flash it to a new chip to replace the faulty one. Thats assuming it is not a more simple component that has failed. I'm quite sure it would not be so easy in practice. Berni

So the ecu isn't going closed loop but you've confirmed that the sensor is good? In that case if you can identify the pins that connect to the sensor then you should be able to trace the lines on the dme pcb to the components. Testing these on the board is potentially very complex due to multiple electrical paths. At that point you're best off examining the pcb itself for what are prosaically called 's**t stains' in the ee world - in other words traces of burns or damage to the components. If you've already done all that and I'm teaching grandma to suck eggs take a pic and I'll show my ee friend/colleague who will identify said part.

Hello Shalmaneser Thank you! I have been through all the fault finding and the sensor currently fitted is a bit lazy but works. I have also tried other sensors that work. The wiring checks out as per Porches test procedure as supplied by our friendly neighbourhood deMort. Here are some pictures. The signal and earth pins are marked on he underside by the tippex blobs. I also included a close up of what I think is the o2 chip. I can also take very high rez (42mp) if required. These are courteously of a slightly buggered iphone 7. Thank you again!

The IC in the second photograph is an LM293 comparator, I can't identify the first one on the bottom side of the board. MC

Hi MC Thank you. I looked that one up, and gas sensors is one of the applications. The other one that looks similar is hard to read, but seems to be marked 302904239 DEX. I cannot find anything about that one. I'm getting the feeling I will have to do some man math on this and justify a replacement DME/alarm/key set on the basis it will come with a working remote head (two if poss) which I do not currently have but want. Remote fobs are approx 250 new, DME sets are 250 bid-500 offered. Dealing at 300 from what I can tell. I still want to fix this one really though. Part of the proposition with this car is that it is an economical fun runaround. Although actually the car has surpassed my expectations significantly and I have really bonded with it. Plus (along with many) I am not working at the moment, so cost is an issue. EDIT: Does anyone know for sure if a DME from a manual car will need re-flashing to work with a TIP? I think it will, but there is very little on this...... Berni

I'll show this to my ee friend but there aren't any failures I can see there which if something is wrong means it's failed in a more subtle manner. It looks like there is a through hole component on the trace, can you show us that?

Hi There Do you mean the other side if these two pins in the middle of the pic?

Yup that's the one

Hi Thought so. There is a big dollop of silicone sealer on to of that. I will attempt removal now....... Tks again Berni

Hi Here we go. Sadly not burnt, it is LVP25.