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Discussion Starter #1
I’m writing you for my 2004 MG TF 80th Anniversary SCU’s assistance.
I tell you the symptoms of the problem that I encountered: i replaced a couple of broken lamps of the dashboard, so I removed the connectors of the dashboard replaced the lamps and fixed in the right place, I did that operation without disconnect the battery ( I know that it wasn’t a good idea ). At this point replaced everything I noted that the red alarm led inside the dashboard was off, then I turned the key for test the light and.. surprice ! I heard a double sound coming from under the gear knob, I tried to start the engine but still sounding and no engine run, so I pushed the open door fob button and this time the engine started. After switched of the engine I got out of the car closed the door and locked by the fob button. The car was locked but no red alarm light on the dash. After that I reopened the car via the fob button, the car was unloked, inserted the key again turned on again and the double sound come again, no red light and no engine start until pushed the open door button fob.
So I read some post here and there and I understood to got in trouble with the SCU. I tried to replace the battery fob as well but nothing changed, tried the sequence for reset the fob but nothing changed.
Now I packed the SCU and both the fobs for send them to you for assistance.
Please tell me when I can send it to you and what’s the procedure.
I remain at your disposal for further inquires if you need.
Many Regards

Luca
 

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'06 MG ZR +120 (HQM) '04 MG ZR 105 (IAB)
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............I heard a double sound coming from under the gear knob, I tried to start the engine but still sounding and no engine run, so I pushed the open door fob button and this time the engine started. After switched of the engine I got out of the car closed the door and locked by the fob button. The car was locked but no red alarm light on the dash. After that I reopened the car via the fob button, the car was unloked, inserted the key again turned on again and the double sound come again, no red light and no engine start until pushed the open door button fob.
................. I tried to replace the battery fob as well but nothing changed, tried the sequence for reset the fob but nothing changed.
Welcome to the forum Luca :)

Note that this is a forum, not a car repair company. The regular posters are enthusiasts who can give you advice on how to make repairs yourself, or can tell you of companies or websites where you can get parts or repairs done, but there are not many techniciams or mechanics here who can carry out repairs for you.

Your car will have the Pektron SCU and a round remote fob - there is no reset sequence for these fobs; they should remain operational even after replacing the battery in them. The Pektron unit is known for some problems, including corruption of the settings for various electrical functions. It usually happens when the car battery has slowly become discharged when the car has been left unused for sometime, but it sounds very much as though memory loss or corruption of the SCU/immobiliser code is what has happened. Sometimes the memory recovers if the SCU is forced to reset (by disconnecting the car battery for a short while, then reconnecting it). So9me people have managed to recover the SCU memory by doing this, but it sometimes takes several attempts before it works.

For better advice and possible repair, I would suggest contacting Paul Brown (technozen-electronics), who knows the Pektron SCU better than almost anyone, and will be able to advise you on the best course of action, and is able to repair/reprogramme the unit if needed. His contact details are on the website in the link, and I would suggest either email or telephone is probably the best way, rather than by text message.
 

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'10 TF135
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Yes, sorry to say, it sounds like an scu relay could have failed, but I'd try Man in the Car's battery disconnect solution as a first remedy.
The Pektron scu common to all but a few of the earliest TFs has (five) infamously poor-quality relays one (or two?) of which control the locking and super-locking/double lock process that we're blessed with.
After 17years I reckon yours ought to be upgraded with high quality units - but ought to at least be checked over.
Go to the Technozen web site for a very comprehensive explanation of the 'Pektron problems' and find out where to send your scu and fobs.
From my own experience I think it's best value-for-money to have all five relays replaced by him, since if one's 'gone' the others (eg window function...) won't be far behind - but imo you need to use his services in some way to help with your problem.
 

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mg_tf
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I second Arnty's advice - if one relay has failed, the other four will be on borrowed time and need replacing as well. The relays are dual relays and so there are in fact 10 circuits that can be switched by them. I replaced all the relays in my SCU myself (supplied by TechnoZen) but it helps to be good with a soldering iron and a solder sucker/solderwick and removing multipin devices from a circuit board.
 

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'06 MG ZR +120 (HQM) '04 MG ZR 105 (IAB)
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There is no involvement of any SCU relays in the immobiliser function in the engine ECU, so a failed relay will definitely not be the cause of the problem. The immobiliser disarms by the sharing of a matched code between the Pektron SCU and the engine ECU.

Further to my earlier post, and having re-read the OP; as it seems to disarm when the unlock button is pressed on the fob, it suggests that the issue may be with the 'exciter ring' around the lock barrel - possibly a connector dislodged or wire damaged whilst removing the instrument binnacle to replace the bulbs? The exciter ring issues a signal when the ignition key is inserted which stimulates the remote fob to transmit the unlock/disarm signal to the SCU. Usually a failure for this to happen is caused by the battery in the fob having insufficient power to respond to the exciter signal (even when it may work fine when pressing the unlock button). If the battery in the remote fob is new, it would leave the exciter ring as being the part most likely to be at fault.
 

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Discussion Starter #9
I’m writing you for my 2004 MG TF 80th Anniversary SCU’s assistance.
I tell you the symptoms of the problem that I encountered: i replaced a couple of broken lamps of the dashboard, so I removed the connectors of the dashboard replaced the lamps and fixed in the right place, I did that operation without disconnect the battery ( I know that it wasn’t a good idea ). At this point replaced everything I noted that the red alarm led inside the dashboard was off, then I turned the key for test the light and.. surprice ! I heard a double sound coming from under the gear knob, I tried to start the engine but still sounding and no engine run, so I pushed the open door fob button and this time the engine started. After switched of the engine I got out of the car closed the door and locked by the fob button. The car was locked but no red alarm light on the dash. After that I reopened the car via the fob button, the car was unloked, inserted the key again turned on again and the double sound come again, no red light and no engine start until pushed the open door button fob.
So I read some post here and there and I understood to got in trouble with the SCU. I tried to replace the battery fob as well but nothing changed, tried the sequence for reset the fob but nothing changed.
Now I packed the SCU and both the fobs for send them to you for assistance.
Please tell me when I can send it to you and what’s the procedure.
I remain at your disposal for further inquires if you need.
Many Regards

Luca
Thank you very much
Luca
 

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Discussion Starter #10
There is no involvement of any SCU relays in the immobiliser function in the engine ECU, so a failed relay will definitely not be the cause of the problem. The immobiliser disarms by the sharing of a matched code between the Pektron SCU and the engine ECU.

Further to my earlier post, and having re-read the OP; as it seems to disarm when the unlock button is pressed on the fob, it suggests that the issue may be with the 'exciter ring' around the lock barrel - possibly a connector dislodged or wire damaged whilst removing the instrument binnacle to replace the bulbs? The exciter ring issues a signal when the ignition key is inserted which stimulates the remote fob to transmit the unlock/disarm signal to the SCU. Usually a failure for this to happen is caused by the battery in the fob having insufficient power to respond to the exciter signal (even when it may work fine when pressing the unlock button). If the battery in the remote fob is new, it would leave the exciter ring as being the part most likely to be at fault.
thanks for the detailed answer I also wanted to say that if the exciter were disconnected the alarm led would still flash or remain off as in my case?
thank you
Luca
 

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Discussion Starter #11
I second Arnty's advice - if one relay has failed, the other four will be on borrowed time and need replacing as well. The relays are dual relays and so there are in fact 10 circuits that can be switched by them. I replaced all the relays in my SCU myself (supplied by TechnoZen) but it helps to be good with a soldering iron and a solder sucker/solderwick and removing multipin devices from a circuit board.
Good evening thanks for your kind reply. I sent several emails to the suggested repair center but they never answered and the phone seems disconnected. could you please check if they are still operational?
thank you
Luca
 

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mg_tf
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Hello Luca,

I'm in no better position than you are to check on whether Technozen is answering his phone or email! However, I looked on his website and noticed it was updated in January 2021 so I think he is almost certainly still doing business. He also runs an eBay shop. Did you make sure when you tried to phone him you used the correct telephone country code (+44) for the United Kingdom and also I believe you do not dial the first '0' in the phone number.
 
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