Which Fault Code Reader & EU2/EU3 MFRU wiring compatability issues

[Edzup Ezzer]

I have (finally) completed the conversion of my 1.6K series from EU2 to EU3 with a MEMS3 ECU and modified harness from K-Maps, (and new injectors, coils, changed the MRFU etc).  However, it won’t start.  No doubt an error on my part somewhere but I can’t find it. 

The battery is good (13.5v at ignition on, 10.3v when cranking) turns over ok but it shows no sign of life.  So I’m looking for a cheap fault code reader to interrogate the system.  Can anybody recommend a suitable fault code reader that will do the job?

Ezzer

[revilla]

I use a CanScan D900 - not expensive, it does the job perfectly well and includes live data as well as fault codes and reset.

Search eBay for "D900 OBDII" - https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=d900+obdii&_sacat=0

The model year doesn't matter, they just added support for more vehicles, they all cover our old Rover ECUs. Mine is 2012 I think. A 2018 model will give you little or nothing over a cheaper say 2016 model.

Just to warn you, MEMS3 seems very temperamental as to whether it will connect or not. It comes down to the sequence in which you connect things:

• Make sure the ECU is fully powered down. After switching the ignition on, the ECU remains powered up for several minutes (it would be running the fans in a Rover!). You can usually hear a high pitched whine from the IACV while it is powered up. If in doubt wait for a good five minutes after switching off.
• Plug the scanner into the OBDII port and power it on, but don't try to connect.
• Switch the ignition on.
• Establish a connection from the scanner to the ECU.

That seems to work every time. It's as though the ECU detects whether there's anything on the OBDII port when it powers up and if not, stops listening.

It should connect using the ISO9141 protocol;  I usually select "Land Rover" as the vehicle type but it doesn't matter much.

[Wrightpayne]

Andrew,

Are these devices universal across manufacturers - will the same one work on my 2003 Porsche and 2012 Skoda?

Ian

[revilla]

Should do. They all follow the OBDII standard. The Porsche does have an OBDII diagnostic socket? Should have for 2003.

[Wrightpayne]

Yes it has a socket - it would mainly be for the skoda now I’ve decided to service it myself.

Ian

[Edzup Ezzer]

Thanks Andrew.  Just what I wanted to know and I've ordered the one you linked to.  Cheers.

Ezzer

[david nelson]

I got one off ebay but does not work. its in a frozen state. unable to reboot it. awaiting supplier response. I should have checked it when it arrived.

 

David 

[revilla]

OK an update:

Ezzer and I have been exchanging BMs (and MFRUs) for a while and finally got to the bottom of what was happening today.

So the basic problem turned out to be that the fuel pump wasn't running. Not at all. Not priming when first switched on and not running when cranking. Jumping 12V into the wiring for the pump ran it fine, but the ECU didn't seem to be able to turn the pump on. The inertia switch and fuse were fine. A replacement MFRU didn't fix the problem.

The underlying cause was a bit twisted.

Ezzer had upgraded from an EU2 engine to an EU3 engine. As part of the process he had sent his Caterham EU2 engine loom and an MG ZS EU3 loom from the donor car to Kmaps, who had hybridised the two and sent him back what appeared to be a Caterham EU3 loom, to run his new EU3 engine in the Caterham. He used an Kmaps EU3 MEMS3 ECU and and EU3 MFRU with this loom. However ...

The internal connections on the EU2 and EU3 MFRUs are known to be slightly different and not 100% compatible. In this case the part of the loom around the MFRU was still EU2 spec, and therefore he needed to use the old EU2 MFRU rather than an EU3 MFRU as he believed. 

Tonight he swapped back to the EU2 MFRU and the car is up and running again.

I did some digging into the differences between the EU2 and EU3 MFRUs and this is what I found:

EU2 MFRU Internal Schematic (YWB10022)

​

EU3 MFRU Internal Schematic (YWB100970)

​

It turns out that the only single difference between them is which permanent 12V supply pin the fuel pump relay switches through to the pump. In the EU2 MFRU, it takes the pump power supply from pin 8/6, which shared with the main relay, and pin 8/1 is unused. In the EU3 MFRU, it takes the pump power supply from pin 8/1. This means that in EU2 wiring looms, pin 8/1 is normally left unconnected whereas in EU3 wiring looms it is connected to a permanent 12V supply.

Simplified EU2 MFRU Schematic

Simplified EU3 MFRU Schematic

So when using an EU3 MFRU in an EU2 loom which has no supply on pin 8/1, the fuel pump will not run. Ezzer sent me a photograph of the larger (output) connector on his MFRU and sure enough, pin 1 had no connection.

Interestingly this means that an EU2 MFRU will work with either an EU2 or EU3 loom, but an EU3 MFRU will only work with an EU3 loom as it requires that additional power supply on pin 8/1. So they are only incompatible one way round.

And here's where it gets really silly. Just to cloud the issue further,​ Caterham's published wiring diagrams for the EU2 engines are once again incorrect; they quite clearly show the internal schematic of an EU3 MFRU embedded in an EU2 loom, which would never work. In fact they show exactly the situation that Ezzer ended up with. If you look extract from the EU2 wiring diagram below (in this case the VVC diagram, but the same appears on the MPi diagram), the fuel pump is not connected to anything, it is fed from a relay but the other side of the relay is just shown as an unconnected terminal!

It should correctly be drawn with the internal schematic for the EU2 MFRU, something more like this:

The odd thing is, on the original diagram there's a black dot to indicate a junction where I have shown the wire joined on in my diagram, but no wire joining ... it's like somebody knew it was actually like that but then kind of forgot when they came to draw the wire!

[Wrightpayne]

Brilliant sleuthing yet again. Well done Andrew and future resource for all.

Ian

[revilla]

Just to add insult to injury, whoever drafted the EU2 engine loom wiring diagram kindly added a little drawing of the MFRU connectors to make sure you get them the right way around. It's numbered backwards!

In order to align with the pin numbers used on both their diagrams and mine, the connector pins are numbered like this:

[Golf Juliet Tango]

Another brilliant pair of posts Andrew!

[Edzup Ezzer]

Conversion of my car from EU2 to EU3 spec which includes the MEMS3 ECU and it’s capacity for map improvements (the reason for doing it in the first place) has been a long and trying project.  Much more trying than I had envisaged as it wouldn’t start despite the ECU getting all the signals it needed to run.  I’ve been pulling my hair out trying to understand where the fault was which prompted my plan to interrogate the ECU with a fault code reader.  Enter Andrew (Revilla) who as many of you will know is not one to be beaten by a problem such as this.  With his considerable help, tenacious and dogged persistence and a lot of hard work (& not to forget his generosity and trust in lending me a MFRU) we, or really Andrew and with some invaluable help from K-Maps, finally got to the root of the problem – the MFRU.  In particular the compatibility of EU2 & EU3 MFRUs with the wiring harness.

As his excellent posts above explain, the story has some nutty little twists and turns but with Andrew on the case we were not to be denied.  We (in reality Andrew) cracked it.  So like so many others I have to say a massive thanks to him for his efforts in helping me sort my car out.  

Ezzer