Roverlike

Mileage in case of MG F and TF cars is written within memory chip in the instrument cluster. This cluster and its electrics is not connected to diagnostic port.
So there is no diagnostic tool which can read or write this information. That can be done with equipment to desolder chip from cluster or read from chip while it is not desoldered on cluster and write it to another chip for another cluster. Also you need to have person who konws where this information is written within the chip.

If I am not mistaken, original poster who started mentioned thred has the ability to delete its first post in the thread. By doing so he will delete whole thread.
It is the right of the original poster and I do not see any problem in that.

EDIT: I just checked and I am wrong. On this forum you cannot delete your own post, only admis can. So ignore my comment.

judiths handyman wrote:

Not yet, next week apparently.
I remain circumspect regarding most experts these days.
I will post the result though.
I wondered if when sold new the cars came with two fobs of if it was an optional extra at additional cost ?

New cars always came with 2 sets of key and remote.

From your errors and emmision test result I am seeing that you have problems with pre-cat lambda sensor. I would change pre-cat lambda sensor for new one and retest. From what you described pre-cat lambda sensor was not chaged.

Delbourt wrote:

It is wrong to assume but presumably re programming the MEMS3 and thereby affecting the interaction with ring around the ignition switch has no effect on the “burglar alarm features”?

Yes, it is wrong to assume that. If passive immobilisation is removed from your engine ECU, that means you do not need your fob to start the engine. That also means somebody can break into your car by smashing window and hot wire your car and they are gone. Yes alarm should sound because opening door will triger alarm, but then just depends how quick they can hot wire your car and be gone.

generous_dad wrote:

This information is very interesting. Thank you.
Is the exciter ring also present and operating in later cars (with MEMS3).

Yes, cars with MEMS 3 have this feature.

Ring I am talking about have nothing to do with rotary coupler. This is ring around ignition barrel where you insert the key and it is directly connected to 5AS alarm box. When key is inserted into ignition barrel ring starts working, inducing fob to emmit signal needed for passive immobilisation to be stopped. When engine is started signal is no longer needed since passive immobilisation is not active. That is all to it. No other purpose of that ring.

He has MEMS 3 MG F which have later Lucas 5AS alarm box. That box have exciter ring around ignition barrel and if fob is on the key ring, the ring will induce fob to transmit signal and behave like you pressed the unlock button on your fob. So in this case he needed to remove fob from key ring to know if passive immobilisation is active or not.

Delbourt wrote:

In answer to the question regarding "can I start the engine with key alone?" , the answer is at this point in time I don't know. I'm fairly certain that the answer is "No" because when I bought the car it only had one functioning fob and key. In other words I had a spare key (and possibly a fob but that fob either needed a battery or re synchronising). The key itself would enter the petrol cap and possibly the door or ignition but not both and not the boot. After a bit of grinding and use of a file I removed some more metal and it would enter all locks and operate each one (but as stated without the fob no engine start as far as I can recall and there may even have been an alarm if tried (but it is a while back now).

If you are certain that you cannot start the engine without using a fob, then you have factory map and your MEMS 3 did not pass through remap process.