Interrogating Lucas 5AS

Please bear with me. Although time is passing quickly I have recently purchased a MGTF 135 2003 registered Dec 2002 build date. It uses the Lucas 17TN key fob to open doors and set the alarm. I believe this is associated with the Lucas 5AS security or central locking control.
In brief I have had a one incident when I opened the passenger side door with the car unlocked when the alarm (horn) sounded.
More recently although not 100% positive we believe that a 4AM car alarm sounding in the locality was from our TF which was locked up in a detached garage. As it was raining and blowing hard no attempt was made to wait and establish without any further doubt that it was the TF and the car was left unlocked but in the locked garage.
"Discussion" with other well informed personnel suggests that variations in battery voltage can trigger these alarms. I believe the battery is in good condition based on other tests.
There is one other potential problem (that for practical reasons can't be investigated at present) and that is the under bonnet switch. This may not be working at all at present.
So my questions are as follows. Can PSCAN be used to investigate the alarm system and check on history stored in the memory of the Lucas system if it has a stored memory i.e. what was the last device to initiate the alarm? Secondly, can PSCAN interrogate the alarm system and check on the condition of the individual components in the alarm logic? Thirdly, there is a totally or at least there appears to be a totally different alarm with rechargeable batter back up. This last system is encountered if an attempt is made to start the engine with a key that is without its Lucas fob. In that case a higher pitched alarm with lower dB is heard. I believe this is the "Sounder-Alarm-Battery backed up" identified as D154 on the wiring diagram. Can anyone tell me if PSCAN can interrogate this alarm to assess its condition, and if so how please?
Any help will be greatly appreciated.

If you have a 17TN fob then yes, it is a 5AS and not a Pektron system.

The features of pscan associated with the 5AS are listed here https://pscan.uk/features/5as.html

You can view the parameters of various inputs to the 5AS in real time, but there is no feature to view an alarm history.

I don't understand why you cannot look at the switch yourself but I'll take your word for it

pscan can tell you whether or not the under (front) bonnet switch is working (with Pektron, at least). My under-bonnet switch wasn't working when I was investigating problems with the EKA (still unresolved!). It was a trivial job to remove the switch, dismantle it, and clean the contacts.

I don't know whether it can recover historical alarm events. If it can, I'd be interested to know how.

Thank you for that, I remember that now after clicking through from the link. When following the link I see it shows or records two conditions high or low.
In the example shown most are shown as high with only the inertia switch as "low".
What does high mean and what does low mean please? How does one establish which ones should be high and which ones should be low?

Thank you for the reply. Apparently no PSCAN will not record history. The reason I can't investigate the bonnet switch is due to the fact that there is "stuff" suspended from the garage ceiling and I can't open the bonnet high enough and the car is at present immobile as I am in the process of preparing to change cam belt and water pump.

Hopefully someone else in this forum can have a look at their car and tell you what "normal" is and then you can compare with your car.

Ok, let us put things into corrrect context.

You have Lucas alarm 5AS system. It uses horns as way of producing sound. You can silence the horn if alarm is activated only by pressing unlock on the fob. You do not have Battery Backed Up Sounder, or any other form of Battery Backed Up alarm from factory unless it is aftermarket install which I serioisly doubt.

Sound you hear when try to turn ignition without presence of fob is from Lucas alarm which provides information that you have passive immobilisation active and without fob you cannot start the car. Actually you can start it for a second or two and then it will stop. If you turn the key in ignition barrel in order to take it out you will stop that Lucas warning sound.

Lucas system does not have any kind of history. So you cannot interrogate it what triggered last alarm sounding.

You cannot interrogate Lucas system in order to show you if larm system is working properly, but there is test procedure by which you can test each lock if working properly. However, be warned that test can pass without any problem but you will still have alarm triggered - you need to find cause of alarm triggering which is what you are trying to do right now.

Note that you can do remapping of engine ecu at people like KMaps or SAWS tuning. In that case you will have engine ecu with erased need for pairing to alarm ecu. Then you can disable alarm ecu by pulling out the fuse of Lucas system and alarm system will be disabled - but also central locking will be disabled as well, so no use of fob will be present. You will not have passive immobilisation any more as well.
How your insurance will react in this case is up to you and your insurance.

Usual sort of problems with alarm triggering in case of MG F/TF are: low battery, internal microwave motion sensor if you have it (can be triggered with bad microwave owen next door or inteference from bad strong electronic power source close to you) - but is disabled if locking by key only and not by fob, broken wires in the boot, bad microswitch in either door which provides information if door is open or closed, water ingress within boonet or boot switch.

Thank you for the response and much valued information. As you say in your response I am trying to find the solution. What i am struggling to grasp here is this. If I use PSCAN and enter the appropriate area for the Lucas alarm why can't I see which one is not working as it should? Could you offer some further guidance to indicate where I find the test procedure associated with testing the alarm system please, and in simple terms does PSACN offer the ability to toggle through each one and change the status of each position, eg unlock and lock door or boot switch etc?

I appreciate that not every function will be present as drawn in the wiring diagrams downloaded from this website. However, the battery up item "D154 Sounder Alarm battery backed up" shown on page 4 seems to feature strongly in the diagrams and hard to see that it might not be present.
Do you know where it might be found if there is one fitted, or more to the point where the space for it will be seen if it is not there?

pscan is reverse engineered from the factory MG Rover diagnostic tool (T4). I can only implement features in pscan that MG Rover put into the T4.

Lucas system is not designed in a way it can be interrogated and that it can show you information which input is not working. In that way PScan cannot provide you service which is not supported by Lucas system.

Lucas system is designed in a way that it receives signal, meaning ground connection from its inputs and then alarm is triggered. If false signal is received it will trigger the alarm nevertheless it is legitimate input or not.

So test can be done in a way that you put Lucas system in test mode and then trigger one by one input and if working as it should horn will sound once.

Test procedure is described by Paul aka Tachnozen here: https://www.mg-rover.org/threads/5as-alarm-self-test-facility.197288/#post-2052558

Regarding Battery Backed Up Sounder - you have Lucas 5AS alarm system - and you do not have it. You are looking into wrong diagram for later cars. This site provides you 4 versions of RAVE (A, B, C and D). Diagram you are looking is C one for MG TFs with Pektron alarm system. You should be looking B version of RAVE diagram for MG TFs with Lucas 5AS system.
Changeover from Lucas to Pektron alarm system happened somwhere mid 2003 I think July starting from certain VIN number.

Battery Backued Up Sounder is under bonnet and surely can be heared instead of horns in whole your neighborhood and certanly is not limited just inside the car. But as I said, you have Lucas alarm system and do not have BBUS.

I appreciate the help being offered as this is a steep learning curve. I have looked in the downloads section and can only see one version of the wiring diagram for the MGTF
If there is another somewhere else I would be very happy to know how and where to look for it.
The only other one I could see was the mgf

This is one information to Administrators of the site - it would be wise to write at above download that it is for MG TF mk2 with Pektron system - since MG F electric diagrams are noted uo to 2001 and 2001 MY.

The above diagram is actualy extract from RAVE CDs. RAVE CDs are bunch of workshop manuals for certain models of MG-Rovers.

However RAVE require installation of complete program in order to use it and can be used only under that program. It is not single readable pdf.

RAVEs you can find under same download section:



You need RAVE B which have manuals including electric diagram for mk1 MG TF with Lucas system.