C20XE Ecu diagram

[alz7551]

Hi all,

This topic has been posted many times over the websites before but there seem to be a lot of differences in the replys. Now that i have looked in to this myself i have become even more confused!!

My GTE has had running problems with kangerooing and being very lumpy (sometimes perfect though!!) I have replaced all the usual sensors with little effect. The next job was to look at the ECU. The ECU that is in the car is a BOSCH 0 261 200 481 (GM 90 410 502). From reading all the posts i have come to the conclusion that this is the wrong ECU and will be looking for a lambda signal. My GTE is a 91 model and has a lamda but this has been cut (by previous owner). I cannot see any spare wires in the loom to suggest that there was ever a connection to the lamda.

All the posts seem to state that by grounding pin 20 this will switch of the lambda sensor. Easy enough until i traced pin 20 and that wire (brown/red stripe) goes in to one of the injectors so believe that i cannot just start grounding that wire.

Another post i have read says pin 28. My ECU does not have a wire in pin 28 (could be problem).

If i buy another ECU (Non cat/lambda) one then that should sort out the lambda signal problem BUT! if pin 20 goes to the injector on the car wiring then it will always go there. Why are all the posts saying to ground this wire?????

Anyone shed any light on this matter because my head is fried!!

Thanks in advance

Alan

[Vinci]

Re: C20XE Ecu diagram

I reckon regarding the age this is a dizzy engine? Then it MUST be pin 20 to ground to switch the lambda off. If it is a coipack engine there si a whole oterh kind of diagram, but that would mean you can not override the lambda and this should get the EML light triggered. Does the latter light up at all on turning the ignition to pos 2?

The diagrams are all online, so after we've distinguished what kind of motronic you are rrunning we'll post up the correct diagram...

[alz7551]

Re: C20XE Ecu diagram

Hi Vinci,

Thats right, the engine is a dizzy one. I totally agree with what your saying after reading all the other posts around the web. I opened up the ECU main plug and found that the brown/red wire ran from there in to the engine and in to the plastic box which sits behind the engine on top of the injectors. There the wire along with another went in to the injector port. (unless ive missed something!!) The EML light is active when ignition switches on but goes off as normal when started.

I have searched online and found some diagrams which show pin 28 being the lambda control wire. I cannot find anything that says pin 20 is, which is causing me confusion!!

does this help anything!!

[Vinci]

Re: C20XE Ecu diagram

It is a little confusing inside the connector and it all depends a little on which model year your engine loom is. On later engines the place for pin 20 is not populated in the loom connector. Which was the case on mine, so I pulled one from a spare cut up loom and clicked it in.

To find pin 20 you have to work from the numbers that are there and count onwards.

Also if you are not running a lambda sensor I recommend to have it measured CO wise to be sure the mixture is okay (not too lean!)

Here:


If you read the text that is printed vertically on the connection of pin 20 it says "not in combination with P32" and P32 is the lambda sensor. That means that without P32 this connection needs to be made....

[alz7551]

Re: C20XE Ecu diagram

Right okay! Pin 20 has got a wire in it from the car loom so guessing that it should go somewhere different to where i traced it, (will try again tomorrow with the tracing!). Have you ever heard of pin 28 being the lamda as i have read on other forums???

I am pretty sure the mixture is too lean as the spark plugs were pretty black when i removed them.

The ECU that is in the car. When i sourced the number it seems it is from a calibra. If i bought an ECU (FP model) which was seemingly non lambda one and plugged it in, would this mean i would not have to ground any wires or is it a case of pin 20 must be grounded no matter what ECU is in if no lambda is fitted??

also "pin 20 is not populated in the loom connector. Which was the case on mine, so I pulled one from a spare cut up loom and clicked it in." Did you change your ECU or why did you have to add in a wire if there was never one there in the first place?!

Sorry if im missing a point here! been thinking of nothing else all day!!!

[Astra Dan]

Re: C20XE Ecu diagram

The ECUs are pretty much the same so I've heard. The main difference is in the loom, i.e. if your car is early enough to be pre-lambda, the engine loom has pin 20 grounded already and there's no lambda wiring present.
If your car is post-lambda, pin 20 has no wiring present and there's a plug for the lambda by the bulkhead on the right hand side. It sounds like yours is a pre-lambda hence no wiring.

Also kangerooing is pretty much an XE trait, I'm not sure if anyone's managed to get rid of it. I think the "breather mod" is supposed to help. Mine's certainly a but unruly at low speeds.

[alz7551]

Re: C20XE Ecu diagram

Thats where i am really not sure. There is a cut off lambda in the exhaust but i could not find any wiring in the loom so either the exhaust has been changed for the wrong one or the wiring has been butchered somewhere that i missed. There is a wire in pin 20 but my tracing has not found it going anywhere near an earth!.

I am going to have to re-trace this pin 20 and see where the bugger goes!!

I did the breather mod last year but having all these other problems stopped me getting it out for a proper run so cant say whether it made a difference or not!!

Thanks for all the help. I will more than likely be back on line tomorrow night asking more questions!!!

[DarrenH]

Re: C20XE Ecu diagram

as above, my 1988 pre lambda gte16v has FP ecu, and so does my 1991 lambda gte16v

pinout is here, although it doesnt sound like it will help you

http://www.astra-mk2.com/0ddball/motronic2.5_pinout.pdf

the ECU earths are on the fuel rail (the ring conenctors on the studs that fix the fuel rail to inlet manifold) so it might explain why a wire from pin 20 runs up through the loom. first you need to get pin20 correct using the above pinout and orientation

you can see for yourself, but pin 28 is the actual signal return from "a" lambda sensor

[Vinci]

Re: C20XE Ecu diagram

A couple of the earths need to be in excellent condition for the engine to run well and safe. Off course the obvious engine to chassis and alternator to block, but a very important one is the maf sensor earth. After reconditioning most of my engine loom last year my engine is running much smoother and it idles steady as a dead horse..

Pin28 is a lambda sense wire, not the control wire.

Black plugs mean a too rich mixture, not lean.

There are no ecu's without lambda control that I'm aware of. All M 2.5 ecu's should have the pin20 control wire function to overrule it. If that is done CO must be adjusted on the trim pot in the maf sensor...

[alz7551]

Re: C20XE Ecu diagram

Thanks again for all your help guys,

I definitely understand the wiring a little better. I got a little side tracked today so not much progress. I did get hold of an FP coded ECU, plugged it in and the car which started but immediately cut out, did this several times before the battery needed to be put back on charge.

More confusion with this as according to all the posts every ECU is compatible!

Not gonna get a chance to have a look till next week now.

Thanks again anyway! Im sure you will hear from me again soon!!

[Vinci]

Re: C20XE Ecu diagram

Fuel filter okay? That does sound like a blocked filter there mate!

P.S. any ECU will work, but there are early ones programmed to work with 2,5 bar FPR and then later ones (still M2.5) for 3.0 bar FPR!! That means if you run a 2.5 bar FPR you could get in to trouble with a later ECU making it run lean. I've know several cases where this has been used like that for a while with no problems though...

[DarrenH]

Re: C20XE Ecu diagram

3 bar ones are M2.8

ident PT from memory

[Vinci]

Re: C20XE Ecu diagram

3 bar ones are M2.8

ident PT from memory

I thought so too, until I was proven wrong. There are SOME M2.5 that were delivered with 3 bar regulator as well...

[DarrenH]

Re: C20XE Ecu diagram

just had a look at my 1988 loom (in fact it has a sticker wrapped round it with december 1987 nice !) mystery solved

pin 20 has a very thin wire, brown with red trace, it goes up into the main loom bundle but DOESNT make it to the injector rail. yes there is a brown with red trace, but that's a thicker gauge which is earth trigger wire for injector 1 (to pin 17 on ECU plug)

about an inch before the large rubber grommet that goes through the bulkhead, the thin brown with red trace from pin 20 is soldered to a bunch of other earth cables, pressed and wrapped separately with loom tape.

did get a bit of a run around because theres a thin brown with red trace that goes to the brown A/B engine coding plug, which appears to intercept the signal wire from the hall sensor (3 pin plug on distributor) didnt know thats how it worked.