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Discussion Starter #1
Hi,

Just in the last week I've had intermittent reliability with the key fob unlocking my 2002 MG ZS, which appears to be getting worse. I've read lots of posts to look for similar experiences and not found anything quite exactly the same.

Either both buttons on the fob work or neither of them work, which suggests it is not one or the other buttons. There is no apparent pattern to them working or not working. I've taken the fob apart, which is 3TXB, and looked very carefully at the circuit board (XP17 V1.7), having read that some joints can go dry. Everything appears to be connected properly, including the legs on the battery holder. The battery is fine, as I had that checked, and I only replaced it about 3 months ago, after it had been working with the previous battery for over two and a half years. When the buttons on the key fob are not working, the immobiliser still appears to recognise when the doors are opened with the key, judging by the behaviour of the red LED in the dashboard which is directly driven by the immobiliser. Judging by the behaviour of the security light on the dash and the indicators if I lock or unlock the door with the key, the immobiliser unit still appears to be functioning even when the fob is having no response, just that it isn't recognising the fob. This appears to rule out most of the electrical connections that I thought might have been responsible, as I know from extensive experience that connectors can become tarnished or weak over time.

I can't just use the EKA code as I don't have it - I bought the car second-hand for £375 and it didn't come with any manuals.

So it appears that the only thing it isn't doing properly is recognising the key fob. This makes me wonder about the aerial, which apparently can be disconnected from the 5AS in order to straighten the path and increase the range, which is my next line of attack.

Anyone got any thoughts? Any suggestions greatly received!

Mike
 

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In the Garage
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When you replaced replaced the battery did you re-synchronise the fob with the car?
 

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Discussion Starter #3
Yes, and it was working fine for the past three months or so. Its just the last week and a half it's started to show any inclination to ignore the fob ?
 

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Discussion Starter #5
No, if the doors won't unlock, the engine won't start either - that's the problem bit!
 

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It could be that some element on fob pcb is failing. I would suggest to ask a question about your fob with Paul at: Technozen Electronics - Home Of Pektron SCU Repair He is the best person on this topic.
If fob is failing with element on it, it might be that you will need new fob programmed for your car, and when you are doing that you might programm spare one as well.
 

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Have you thought to open and inspect the Button inside where it presses onto the micro switch. I had a similar problem with My Pektron fob and found that the underside of the 'button' has a small rubber protrusion that connects with the micro switch . This had malformed over time . In your case it could be that dirt has entered and the button not doing its full travel. Just an idea. Electronics usually work or are hardly ever intermittent ergo I would opt for a mechanical problem with the fob first.
 

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Discussion Starter #8
That's a great suggestion, and i know from experience also that the button you're pressing reaching the end of its travel before the switch is activated is something that occurs in all kinds of devices. On the Lucas fobs however the rubber button has quite a lot of travel, and i can hear and feel the microswitch operating underneath. Plus, i actually tried it outside of its case, and also either both buttons work or neither of them work, which indicates a common point of failure rather than failure in the individual buttons.

Where I'm at now is removing the centre console to get at the immobiliser itself. And already the two bolts holding down the front and rear consoles have sheared off rather than undo ?. And I'm temporarily stymied by not having the extractor tools for the stereo that was already fitted when i bought the car. Although cheap to buy, they won't arrive until Saturday ?
 

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Discussion Starter #9
Update: Ok, I've got the centre rear console, and then the front console off - and the two bolts holding down both consoles didn't undo, they just sheered off :-/ But still, I've now got at the 5AS. I've unplugged it and plugged it back again, and that hasn't made any difference, as I had hoped that the contacts would somehow be tarnished and that would made the difference. Couldn't see an external aerial connector that someone described as being a yellow cable. it still doesn't work, and a couple of hours ago I ordered he EKA code from Radiocodes.co.uk, but ordering via the web on my phone and paying via paypal seems to have skipped a step where I give them my email for them to send the code - no code was displayed, and now nearly two hours later no email has been received, even though I wrote to them an hour ago. And their phone number is going to voicemail even though it's within their stated working hours, so not sure what's going on there.
 

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Discussion Starter #10
Ok, further update: the code did arrive, although without any accompanying instructions, which meant i had to resort to this forum to find out how to use it. I didn't have to wait 5 minutes, and on turning the key to the engine on position the immobiliser came on and beeped once, then went off. Engine is now running. What a relief! Now i just have to find a convenient time to send the immobiliser, fob, and spare new fob i just bought to be fixed. So in the meantime I'll be driving around with a half-disassembled dash
 

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Discussion Starter #11
Further update: I ran the engine for about 20 minutes and then got out of the car, without using the key fob, believing that the immobiliser is now locked off, until I use the key fob. However, about an hour later when I returned to the car, and having taken the fob off the key ring so I wouldn't press it by accident or out of habit, the immobiliser was on again and the car would not start. I tried the unlock procedure again using the same code, but this time it would not work. So the immobiliser seems to have come on again by itself, and the EKA code that worked only about a couple of hours ago is now not working. Any clues? Is it supposed to only work as a one-off? It's looking increasingly as though I will have to send it off to get it repaired.
 

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Discussion Starter #12
Ok, it appears that on some models the EKA code was supposed to only work once, and then need to be repeated each time you start the car, which is a pain. But not clear why it's not working the second time round.
 

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Discussion Starter #14
I disconnected it to take off the cover and have a look inside, and also to break and re-make the electrical connections in case tarnish was preventing it from working properly but i connected it back up before i tried using the EKA code the first time and have not disconnected it since
 

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Ok, what i hope is the final update! Paul at Tehnozen Electronics said he thought it was probably the receiver circuit that was failing. I managed to get another 5AS from a friend's ZR he was breaking with fob, and sent both 5AS off to Tehnozen and all three fobs including the one i got off eBay. It turns out the eBay fob, despite being in a new case, is a 3TXA and therefore no use to me, but at least i have two fobs and a working 5AS. Paul copied the settings from the old to the new one so the ECU did not need to be programmed to match. What a blessed relief to have it working again, and i also notice that the locks respond instantly to the button press now, compared to a very pedestrian response before, even when it was working reliably. So i can comfortably endorse Technozen Electronics, and a responsive turnaround as well. I hope that's the last you hear from me on this topic!
 
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