S52 obd2 swap wiring help

[Vegan m3]

Hello everyone I'm new to the forum. I need help wiring my s52 obd2 swap. I have a 1997 318ti manual and my donor car is 98 m3 sedan also manual. My 318ti only has 2 main harness connectors and the m3 came with 3 connectors. I originally thought I can just plug the 2 connectors in and it would fire right up. But that's not the case, now I'm stuck and not sure which pins need to be moved around. Any help is greatly appreciated. Thanks for reading.

[wodcutr]

Read the OBD2 wiring questions thread in this section. I just finished doing mine and had similar issues but figured it out and posted what I did. Pm me if you want to discuss further!

[Vegan m3]

Hi woodcutr, thanks for responding. I would have sent you a PM but I don't have 5 posts yet. I have been looking through your old posts and I have not come across the wiring part of it, unless I overlooked something . I saw the posts about the asc wiring and aux fan.

[wodcutr]

I believe the car will run without you doing anything really. My guess is that you are dealing with an EWS issue. You have to use the M3 DME, EWS, and key to get it to run. Iirc the only real pin swapping that needs to take place is the 9 pin from the smaller connector needs to be put into the 8 pins place in the larger connector. The other stuff is all just convenience wiring for aux fan, econometer, fog lights, etc.

[Vegan m3]

I have swapped over the ews2 module , the DME, and I also taped the two keys together temporarily . The car is not turning On at all. The lights on the dash do not light up either and my battery is brand new. What would be the cause of nothing turning on.? Without swapping over wires in the main harness, would my dash still light up when turning the key on?

[wodcutr]

Yes the dash should light up when you turn the key on. Did you relocate the battery to the trunk? The ti had the battery in the front so the engine harness had the proper connectors included in it. The M3 harness has no positive battery connections other than the ones for the + tower link and a trunk installed battery has a fusible link that also comes into play. You obviously aren't getting power from the battery!

[Vegan m3]

I got the dash lights to turn on. I did not notice that the distribution block has 2 terminals that do not connect to the rest of the circuit, Greenhorn mistake lol. I swapped the chip over from the m3 key and still no start. Now I think it could be ews issue. I am using the ews module from the m3 along with the DME.
The wire swap you mentioned in earlier post, does that need to be done for my vehicle to crank over?
I apologize for asking such newbie questions, I appreciate all of your help.

[wodcutr]

I don't believe that would cause a no crank issue, only a CEL. Your EWS is probably not aligned. If the chip is not being recognized you should get a code.

[Vegan m3]

Thanks woodcutr, for answering all my questions I really appreciate you helping me out. I got my car to fire up today

[wodcutr]

That's always a great sound and a relief! Enjoy your car.

[summerlinbrayden]

What ended up being the issue?

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