Picture sequence
Alarm System of the MGF (TF)

Lucas 5AS Security system http://www.alarmremotes.co.uk/new_page_4.htm
Landrover and Discovery, Mini/100/200/400/25/45/MGF. 433MHz YWX101220 (A) OR YWX101200
(Japanese Blipper version Part Number with different frequency 315MHz is YWX 100870 )
Spare Blipper aswell available from
or i.e. cheapest from


The EKA code could asked at your friendly dealer, or try this service

See at Tom's site

See for manual action

The key fob transmitter uses a 3V battery (No. 2032).
The MGF was delivered with 3TXA until about VIN 39xxx (app 1997)
and 3TXB since this time until the major change to a circular housing transmitter with included 'Transponder'
The Transmitter 3TXC from a Land-Rover Discovery should work fine in the system and should be much cheaper. 17TN as well.
Nissan Micra dated about 1996 uses also the 5AS Immobiliser with 2 button blipper.

The difference between 3TXB and 3 TXA is not related to frequency.

The difference between 433MHz and 315MHz version

David from Alarm Remotes http://www.alarmremotes.co.uk/index.htm

if you have a 1239 resonator (TO39-3 Case) then its 315Mhz. If you have a 1207 resonator then its 433.92Mhz.
(Resonator, 2-Port, 180° Tol. = ±75 kHz) RF Monolithics

The only way to tell reliably what frequency the fob uses is by the number on SAW resonator on the PCB. A lot of MGF's in the UK are 315 MHZ. But the majority are 433.92Mhz.

if you have a Lucas 5AS security ECU you will see on the label a black 25mm circle with a letter inside it.
Letters M/K/S/T all denote 315 mhz units. (There may be also be others)
Letters A/H/L/R all denote 433 mhz units.


(For the electronically challanged, its the small (TO39-3 Case)
round silver component on the battery side of the 3TXA fob).

bottom LH, the frequency related electronic componentnt

Solution for the Alarm Blipper working range Problem ?

Carl , Sweden . Message to the MG Cars BBS on 1/10/1999 15:36

Hi all !

This is going to be a long thread about blipper system for our beloved "F".
For receiver I will use "RX" and for transmitter "TX".

The keyholder contains the TX circuit and after doing some measurements on my 3TXA the following was found:

TX frequency. 433,895 MHz .
Modulation : Amplitude mod , (AM).
Output power at module before modulator : Approx. 1,5 mW at 3,1 Volt battery .
Type of antenna : Printed circuit loop tuneable with aid of small soldered adjustable pin.
All in all output spectrum and power at distance of 10 meters measured with L/4- whip at spectrum analyser showed fair enough signal to be accepted of a not too deaf RX !

So what is the problem then?? Well, as stated some time ago in another thread

- to make a small decent TX isnīt that big deal
- to make a good RX that works in todays polluted frequency spectrum is another story !
Without having taken the RX apart (yet) I can bet that it is a simple so called "superregenerative" receiver - known to radio amateurs as the infamous "rushbox".
This is a cost effective way of solving the RX problem but it also generates a few problems;

DESENSING: Nearby transmitters (not necessary spot on our frequency ) will make a not so good RX more deaf to wanted signals. This means we have to decrease distance to get any action at all.

PULLING: The nature of superreg. makes it fine for AM signals but if another signal off freq. is stronger this will make the RX "lock" onto this signal and further decrease in distance is needed.

SELECTIVITY : This is the costly thing, superreg. is bad news here.

FREQ: OFFSET : As RX and TX may have different temperatures we can have diff. in freq. This is today to some extent solved by the "SAW-resonator. At least the TX has a SAW.

ANTENNAS: For the "bliper" there isnīt much of a choise, size demand small antenna and then for cost reasons printed circuit board loop resonator is the thing to go for. At RX end there is of course more space and normally the antennas on other manufact. are situated as free as possible. In outer mirror casing is one often used spot. In our case the yellow quarter-wave cable under dash is a bit displaced for optimunm reception ,even worse so when coiled together with all other cables !

So summing up I think that the main problem lies in the RX. Maybe a thin coaxial cable from the box and putting the antenna in a better place will give improvements , but this has to be found out. I will take a look at the RX this winter as car is on stands , my range is around 3-5 meters with straight RX-antenna - so not that impressed..... Regards , Carl.


a replacementkit is availiable for that high value part. I think its interesting for you (one of the oldest MGF) too: YWX101010 - repair kit for the remote blipper. It contents the both casing? (housing) halfs and the rubber button thing.
YWX101070L is the same part at Land Rover.(LR YWX101220 433 MHz complete blipper)

(c) Carl G. B. Sweden, translated by Dieter Koennecke 02.10.99

Housing as Spare Part availiable:

YWX101010 - repair kit for the remote blipper.
It contents the both casing halfs and the rubber button thing.

Access to the self test facility is obtained as follows:-

(The following steps 2 to 4, must be completed within 2 seconds, in order to induce the ECU to enter the self test mode.)

1) The vehicle must be in disarmed mode, unlocked and with the ignition switched off.

2) Lock the driver's door using the driver's door sill button.

3) Turn the ignition ON, OFF then ON again and leave it ON.

4) Unlock the driver's door using the driver's door sill button.

Confirmation that the test mode has been successfully entered is given by the horn sounding a short beep. Once in self test mode, the volumetric sensor (if fitted) is powered up and the vehicle is in an immobilised state.

If an ECU input is then seen to become active i.e. to go from an open circuit to a short circuit (or earthed) condition, the security LED will give a short flash to indicate this.

When the system is in the self test mode, operation of the appropriate switch by moving the associated panel or linkage will instigate the test on each of the following circuits;

1) Driver's door courtesy light switch.
2) Passenger door(s) courtesy light switch.
3) Bonnet open switch.
4) Boot open switch.
5) Driver's door key barrel switch. (Not on 100 models)
6) Boot key barrel switch (Not on 100 models)
7) Driver's sill button "up" switch.
8) Driver's sill button "down" switch.

Switch tests need not be made in any particular sequence and any or all may be tested as required.

Correct operation of the circuit being tested will be denoted by the single flash of the security LED and the same circuit may be tested repeatedly if necessary.
The self test mode can be terminated at any point by switching off the ignition.

Failure of the ECU to enter the test mode will probably indicate that it is not receiving inputs from either the ignition power supply or the driver's door sill button switches.


The test facility may also be used to check the operation of te volumetric sensor, either ultrasonic or Doppler microwave (if fitted), by performing the following;

With the system in self test mode and the remote handset previously programmed and synchronised to the vehicle being tested, press the unlock button once.
The ECU will now disregard inputs from it's associated switches, and will instead, give a confirmation flash on the security LED to indicate that the volumetric sensor has been triggered, the action of which can usually be induced by waving a hand in front of the sensor.
The self test mode can be terminated by switching off the ignition.

Replacement Option

Paul Jameson B.Eng.
Electronics Engineer / Director
Avon Automotive Diagnostics Ltd
Tel +44 (0) 1789 450808
Fax +44 (0) 1789 773262
*Rov 2 Fob* model.
Can be adapted to the ECU without a visit to Testbook.

The MGF Immobiliser and Alarm System
Volumetric Sensor

The old version was YWC 103040 up to WD030081
YWC 105910 from WD030082 to YD525771
cable YMQ103410 required to convert the connection.
Part # YWC 000690 from YD 525772 on

the volumetric sensor YWC105910
plug with 4 positions from the notch downwards:
1 white.black
2 brown-black
3 grey-white
4 black (ground)
sticker on the rear: DA 58XX ALARM SENSOR from GEC Plessy Semiconductors Frequency 2.446 to 2.454 GHz
Rover YWC105910 Lucas 52010452B GPS DA5819-002

The volumetric sensor behind theT-Bar

The MGF Alarm ECU YWC105330 (Mk1) (Receiver)

Insight to the high integrated receiver (Type 'A', so 433MHz) . It contents a LUCAS ASIC. Not all connector positions are in use. The white one is 7 pos. the grey about 21 pos in use.. The small module carries RF components. The large parts look like bi-stable relays.

if you have a Lucas 5AS security ECU you will see on the label a black 25mm circle with a letter inside it.
Letters M/K/S/T or B all denote 315 mhz units. (There may be also be others)
Letters A/H/L/R all denote 433 mhz units
TRW 5AS Body control module. It is fitted to Rover Mini / 100 / 200 / 400 / 25 / 45 / MGF from May 1995 to present.

The location of the alarm ECU and the aerial behind the dash

Some cars suffer from false alarms cause of to sensible setup of the volumetric sensor behind the T-bar. The alarm goes off without any visible reason

The solution is almost a reset of the alarm ECU
From VIN WD030082 onwards a modified Alarmsensor YWC105910 gets installed to the MGF.
The sensor must be adjusted in sensitivity with the dealers Testbook Equipment.
(Change at older MGF possible if cable YMQ103410 gets added to convert the different connection).

Brian, Belfast (message to the MG Cars BBS)

Bruce put the test below up some time back and I copied it and have it below. I have found this useful to find the fault.

Try this
1. Ensure doors, bonnet and the boot lid are closed.
2. Sit in the driver’s seat and close the door.
NOTE: The next three actions must be carried out within 2 seconds.
3. Depress the driver’s door sill button.
4. Switch the ignition on, off and on again.
5. Raise the driver’s doorsill button.
If the test mode has been entered correctly, the horns will give a short beep and the engine immobilisation buzzer will sound.
Opening either door, the bonnet or the boot lid, or operating the driver’s door sill button, will cause the alarm LED to illuminate for approximately one second. If the LED does not illuminate, there is a system fault.
The volumetric sensor can also be tested while in test mode. To test the volumetric sensor, press the unlock button on the remote handset several times. The alarm LED will illuminate for approximately 1 second each time movement is detected in the vehicle.
The test mode is cancelled by switching the ignition OFF.


On EKA code:
Dave Morris T6 DCM, Gwent, United Kingdom

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
How to unlock with the EKA, from Roger Parker MGOC

MGTF transmitter

notice 3-button version
made by CEL
Notice, this one will not work with older MGF.
This transmitter was used in the MG ZR/ZS also, but the ECU's are all different
You must have the affiliated Barcode to adapt this Transmitter to your Alarm ECU with Testbook.

That barcode may be stick inside the MGTF service manual or gets supplied with the package of a new transmitter.

Pektron SCU YWC001540 YWC001541

Relay used Fujitsu Relais Blinker
Fujitsu 512ND10-WF / 512ND10-W1 (size 16.2 x 24.0 x 14.1mm)
(discontinued !! may use FBR51/52 or FTR-P4 (not pin compatible))


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