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Engine transplant ECU problem

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I recently transplanted a 2002 3.2 into my 2001 2.7 car. I am unable to get the car to start with the donor car's ECU - lights come on in dash but no power to the starter. I have it running poorly on the 2.7 ECU - I get a P0102 MAF code with periodic misfire codes.I installed the donor ignition immobilizer with the donor ECU but still didn't get power to the starter.What am I missing?
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So you installed from the donor car...

a.) ignition assembly

b.) use donor car key (with it's pill)

c.) immobilizer (under seat)

d.) DME (ecu)

If you do all of those things and all the pinouts match then there must have been something wrong with previous car's setup or the donor set is not matched

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I thought the immobilizer was the box on the ignition assembly. It's under the seat?

Since the donor car was an '02 ... and the receiving car is an '01, what problems will occur if I change all those parts? How do I check the pinouts?

The engine wiring harness from the '02 stayed with the engine and all the connectors fit neatly in the '01.

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Immobilizer is under drivers seat. You must change that too.

Donor immob/dme/pill in key must all match.

Wiring harnesses must match (otherwise you need to rewire, but prob better option to get another donor set)...

(green box behind key not so important IIRC)

If all the connectors match, I think you should be OK.. IIRC 2001 and 2002 boxster should be compatible both use DME 7.2.

boxster didn't change DMEs to 7.8 until 2003 (not sure about immobilizer, but I think that should be oK too)

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OK. ECU changed, immobilizer changed, ignition parts changed and the "pill" installed in the key. Now it starts and runs well.

Oil level indicator blinks, doesn't provide oil level and then times out. Fuel level reads empty, red low fuel indicator light flashes non-stop, high beam indicator doesn't light, windscreen washer fluid low indicator light is on, airbag light isn't on and I had the driver's seat out with battery connected - I think it should be on. What other electrical items might not be working correctly?

Are these things that can be fixed with programming or do I have to change sending units? Hmmm.

The engine runs fast and smooth. Trade offs are part of life.

Thanks for the help.

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Model years 2000 through 2002 were somewhat tumultuous for Porsche and instrument clusters.

The clusters changed just about every year, and even possibly within years.

Assuming all the connections are correct, it is possible your cluster is not fully compatible with your donor modules and engine.

For example an S cluster might be slighlty different than a non-s cluster.

Ideally you would want to match the cluster to whatever car it came from (or one that had similar options).

If you did something like put a manual in a tip car or vice-verse, etc.. then you most certainly have a compatibility problem that coding probably cant solve. It's been a while since I've been in the PST2/PIWIS, perhaps there is some coding that could help some of the instrument cluster stuff, but probably not all of it.

Perhaps someone else can chime in on this.

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I have reviewed the wiring diagrams for the two model years and compared what I think are pin numbers for each connector in the DME, the central locking unit and the instument cluster. All the pins appear to be the same. I'm no electrical engineer and I may be reading this very wrong. However, I'm reading each diagram the same, e.g., looking at the diagram for the instrument cluster, "B26 Turn Signal Left" would indicate that pin B26 was the wire for the left turn indicator in the instrument cluster. It reads the same on each of the two model year diagrams. And so it is with each of the diagrams I reviewed for each area in each model year.

Any thoughts? Hints? Maybe voltages or resistence is different for sending units? Maybe the diagrams are only representative and not an indication of how the cars were actually built? I'm reading the diagrams in the Porsche Technical Manual for the Boxster, group 9, circuit diagrams, Part 2 (from '00 model) printed October 1999. Because they were printed before the cars were actually built, I guess they could have made changes after the printing? Anyone have a copy printed at a later date - after the cars were actually built?

Thanks again for your help with this.

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In my previous post I mentioned that the instrument clusters have changed many times, and especially from 1999 through 2003.

The 1999 wiring diagrams are probably of no use to you.

If it were me, I would try to source the specific instrument cluster year that went with the engine/ecu/immo combo you installed in your car.

My guess is that you are going to be fighting an uphill battle trying to re-wire what you've got...But if you want to give that a go....

You can buy the specific wiring diagram pages from Porsche PIWIS tech site (you would want one for the model year / model type) for orig and donor cars. Coding could also be important, for example if it was a tip donor into a manual car.

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Both cars have manual transmission.

I do understand that there are variations in cluster. I didn't realize I had wiring diagram that was printed before the cars were built until after I'd checked all pins.

I'm using the chasis wiring harness that was in the 2001 - I didn't want to dismantel a perfectly good chasis to change a wiring harness - maybe I should have considered that. I kept the engine harness with the 2002 (they looked the same upon visual inspection, though I realize that individual wires could be located at different pins) when I put it into the 2001 chasis. All the connectors plugged right in.

The ECU, ignition, and central locking unit all came from the 2002. I am told by the previous owner that they all worked together without problem. Unfortunately, he sold the cluster, along with some other unrelated parts, before I bought the rest of the crashed car.

If the wiring harnesses are the same for each model year - are they? - then I should be able to identify which cluster I need by looking at the engine serial number? or would it be better to use the numbers off the ECU or central locking unit?

Depending on which cluster I need, It might be cheaper to flash the ECU as long as that is possible. I talked with one company that sells ECU software and they wanted the 3.2 ECU. Is it possile/realistic to reflash the 2001 2.7 ECU for the 2002 engine?


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Also wondering if I should have used the 2.7 engine wiring harness on the 3.2. I left the harness on the 3.2 and all the connections fit and there were no unused plugs. I imagine that the pin placement could be different in the ECU connections, though.

I did change the fuel rail to the '01 style with pressure regulator on the rail and the fuel return line in place. I used the injectors that came with the 3.2 after seeing that the injector part number is the same for both engines.

Haven't had a chance to look at the engine serial number yet.

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When you are creating a frankenstein there is not a ton of documentation on what is compatible with what and what will work. You may have to do some experimentation unless someone has done this before.

If it were me, I would use the 3.2 engine wiring harness, because you want (most importantly) the harness to match the engine. But also it should match that up with what the ECU expects. If the car runs fine and you just have instrument cluster problems then that part of it (the engine harness and the ECU are probably close to if not 100% correct).

The harness with the 2.7L is different, however probably not drastically different. The 3.2 might just have more connections for S model options. But he base stuff like oil sensors/etc. should match up. You would need to look at the wiring diagrams to be 100% certain.

I wouldn't mess with the ECU anymore (because flashing that can cost $1000 and trust me is a major pain/black magic art). Besides, you already have a working combo of keys/immo/ECU which is really the hardest part of the whole equation. Besides re-flashing the ECU is not going to get you anywhere because all it might do is update the fuel MAP from 2.7L to 3.2L, really you are going to have the same thing as you have now.

At this point that leaves a few possibilities.

1.) the main car wiring harnesses

I tried looking this up, but didn't get very far. If you want to PM me the VINs from both the donor and original car maybe I can help more.

2.) coding. You may need to poke around coding on the instrument cluster and ECU using a PST2 or PIWIS.

3.) the instrument cluster

There are significant differences between a base model 2001 2.7L and a 2002 3.2L S model.

Without knowing all of the options on both cars, here would be my best guess for the instrument cluster part numbers...

2001 2.7LP/N 9866412030670Cm481 - 5 speed manualm016 - standard model2002 3.2LP/N 98664123302FHBm480 - 6 speed manualm008 - S model (3.2L)m659 - on board computer

I don't like spending other people's money in this situation, but my best bet would be on an instrument cluster would be all that you would need at this point and it hopefully would be plug and play. However you may want to look at the main car wiring harness details in a little more depth first.

If that doesn't work then you are looking at transplanting the main car harness and/or using a PST2 or PIWIS to change coding.

You can pick up a used cluster at a place like DC auto for about $500.


IF you try that you may want to find out what their return policy is...

Edited by logray
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Also to your question about PIN placement for the ECU between 2.7 and 3.2 the answer is that they should be the same because both of those model years (2001 and 2002) share the same DME version 7.2.

Ok, dug a little deeper for you...

The main car harnesses are built specific to a VIN and it's option codes. There are not multiple part numbers.

98661290300 $5700

However considering some of the instrument cluster functions work, PLUS the immobilizer works I would guess the harness is very close already.

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I've been working with a few folks on transplanting 996 instrument clusters into Boxsters. I've compiled a bit of information about them. I'm not sure it will help with your problem, but if you send me with a PM with your e-mail, I'll be happy to share it with you.

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  • 2 weeks later...

I looked at the decoder. Nothing significant that I could tell. Seat heaters, leather seats, storage unit in console, turbo look wheels, radio type,cruise control, CD storage. It didn't list OBC. I couldn't find a couple, though - C02 or 239

I looked at the engine and the serial number was not readable. I've seen photos of them on other engines and this was one had a nearly smooth surface. It looked like there may be some numbers made with a pin punch (rather than the usual number punch), but the lighting and difficulty getting under there made it unreadable. I may try to get it on a lift where I can move around easier. I tried putting some grease pencil on the surface and then carefully wiping off the excess to leave some in the dots - still couldn't read it.

Is the number on the option sheet starting with M96 the engine serial number? M9621-672 or part of it?

I ordered the cluster from DC - and will try that when it arrives.

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M9621-672 belongs to a 2002 Boxster S 3.2L.

The S models are almost certain to have an OBC.

However, the engine serial number can be totally different from that, and what is stamped on the engine case would provide the most accurate info.

If someone scratched off/removed the original serial number it's going to be nearly impossible to tell what the core is aside from tearing it apart.

GL with the cluster, I hope that solves some of the issues, although you may still run into problems with fuel level sender/etc.

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I managed to get an email response from the engine builder who says that the engine was built with the stock 3.2 cams and that the note on the invoice was part of a list that describes the process for either a Boxster or a Carrera.

So, now I'm looking for a way to get the stock map flashed into the ECU.

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If the heads on the engine are truly from a 2002, then the 7.2 DME should basically be compatible with the original variocam system. This would account for why the engine runs with either the old or new DME. That being said, without the serial number or knowing what is actually inside it's hard to tell what is actually in the car at face value.

For example, you can run the 2002 heads on a 2003 block. There are only a few compatible options there.

IIRC it was not until 2003 when the 986 moved to the Variocam Plus system, whereas the 996 moved to VCAM+ in 2002. Totally different cam operation requiring different DME's, wiring harnesses, etc.

Returning to stock would be my first priority, most of the time when I read about the frankenbuilds with these cars they are only successful when left in the hands of the professional, but keep the info flowing, and hopefully we can get you up and running.

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