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MG MGF Technical - Key broken can not start MG _ HELP

HELP someone please!!! My key fob has fallen apart and I can not start my MG. Work at 6 in a.m. HELP

1. Is it possible to bypass immobiliser?

2. I have a new keyfob, do I have to go to a dealer to get it programmed?

p g earlington

No-one here is going to tell you how to by-pass the immobiliser, so dealership programming is the only way to get a new fob to communicate with your car.

The alternative would be swap the old electronic gubbins into the new case. That way you can avoid reprogramming.


Thanks Chris,

Yeah, was a bit irresponsible to expect an answer from here!!! Oh well, will have to get my walking boots on in the morning.

The problem with swapping is that the 'block' for the 'open' button has completely come away from the circuit board...hence, no chance of swap over.

Oh well, perhaps the reprogramming wont be too expensive now that I have a new fob (ta ebay)!!!

Besides documentation to prove ownership, is there anything else I would need to take? Any info from the plate under the hood for instance?
p g earlington

Rover did allow for broken key fobs you should have an emergency access code (4 digits) in your documentation also sometimes on a little grey clip that dangled off the spare fob and instructions for using that - basically turn the ignition key n times are in the handbook.

Early codes were incorrect see archive.

I hope you got the same type of fob as your original (shown on back of fob) and yes a dealer will have to program it for you.

Don't confuse the emergency acces code for the radio code which you may come across in your search.
Jon Baker

The "block" that has come off is only a small metal frame and it has a yellow rubber button through it. Even if that has come off, you can still use the contacts on the circuit board by using a small bit of wood or a tooth pick.
If you still have the parts, the small metal cage and button will just clip back on.


Good Morning Folks,

Thanx all for your help. I have just come off the phone with a Rover main dealer.

1. I have to get the key access code in order to bypass the immobiliser so that...
2. I can take the car to the dealer so that they...
3. can reprogramme my new fob...
4. Which shows 'LUCAS 3TXB KEY' on the back...
5. They old key fob shows 'LUCAS 3TXA', the A & B
difference in the number, will that cause a
6. Most annoying part, having to pay £20 for them to
go to a website to get the access code for the key.
p g earlington

The 3 types of square fobs (3TXA, 3TXB & 17TN) are interchangeable. However, there are 2 different frequencies that these fobs operate on - 315Mhz or 433Mhz. You need to have the 433Mhz for the UK.

Ralph Gadsby

Hi F'ers,

Ok, the continuing saga of my broken key fob.

Tried the Key Code and the actions required to bypass the immobiliser – didn’t do the job. May need to check out the door lock mechanism.
Went back to the broken fob and tried ( )'s suggestion and put a key across the 4 mini blobs of solder and managed to open the doors and get car started. Hurrrrrah!!!
Took car to dealer. (Vikings –Herald Industrial Estate, West End, Southampton). Now here's the rub…I bought a key fob from ebay for £11 approx. To programme the fob cost £31, a reasonable total of £42 approx. If I had bought the fob from the dealer and then to program it, the total would have been over £145…£98 + vat for fob and cost of programming!!! The reason/excuse given was that Rover parts were becoming more and more difficult to supply (rubbish). While I was at the dealers, I also bought a new cut key = £11, again, a reasonable price.
So now, I can open my doors at the push of a button, just as God intended!!!
p g earlington

Oh dear - so many complex explanations which are unnecessary! On my MGF I have opened and mobilised it with the key alone without the immobiliser working. Each car has a uniqiue sequence of turning the key in the door, a bit like a single combination lock on a safe. Look in your manual and it will tell you how. I have tried it once and it works. But you need the magic number which on mine came on a small card with the radio code, Car ID no. et al.

You should also be aware that there are a number of EKA codes that were issued around 1996 that are incorrect. Two of the digits in the incorrect code have to be altered (I think by adding 1 to one digit and subtracting 1 from another). I believe that the details are listed on Dieter's wonderful website.
Ralph Gadsby

Traditionally MGR dealers used to increment the 2nd and 4th digits every time they sold a car on - just to ensure the previous owners couldn't get back in to their old cars

eg access code 1234 would become 1335 etc

Here ia a bit of useful info on fobs, click link

Dave Morris T6 DCM

This puts some light on the reason for the funny increments on the 2nd and 4th digits.

Sounds reasonable

This doesn't explain why I have to add one to the 2nd and 4th digits for my key to work. I bought the car brand new from a dealer.


Is it possible for a garage with the Test book to let you know the EKA code for your car? I ask this because once I had to replace the MEMS and immobilizer because of malfunction and got only one key fob back -and not EKA code-. Other options?
JM Vega-P.

This thread was discussed between 03/07/2007 and 06/07/2007

MG MGF Technical index

This thread is from the archive. The Live MG MGF Technical BBS is active now.