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Faulty central locking - E46 - failed GM5 control unit

 
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Charles
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PostPosted: Fri Jan 12, 2018 1:05 am    Post subject: Faulty central locking - E46 - failed GM5 control unit Reply with quote

Advice to E46 owners

Returning to my car at the end of a busy day at school, I pressed the unlock button on the key fob and the lights flashed as normal. Unfortunately, the doors failed to unlock Shocked

After locking and unlocking a couple of times more with the same result, I was able to unlock the driver's door with the key but that was it. All the other doors remained lock and I was unable to unlock them by pulling the interior door handle or activating the central locking button in the console.

To cut a long story short, these are the symptoms of a failed GM5 control unit - and specifically, the two relays in the box that control the door locking.

This is a common fault for the E46 and it appears that 15 years and 308000 miles is a very good life for this unit. The fix is either to replace the whole box (expensive) or replace the two relays (about 1.5 hours work by someone who knows what they are doing).

A repair is now scheduled and apart from the obvious inconvenience of being only able to access the car via the driver's door, through the windows or the boot, the car is perfectly functional
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Charles
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PostPosted: Sun Jan 14, 2018 1:19 am    Post subject: Reply with quote

Strangely, it's started working again Shocked
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Charles
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simon13
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PostPosted: Sun Jan 14, 2018 11:56 am    Post subject: Reply with quote

mines the opposite i've central locking but my fob won't work the antenna has broke in the tailgate
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AidanB10
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PostPosted: Sun Jan 14, 2018 11:44 pm    Post subject: Reply with quote

Had it happen to my old Touring too

Mines decided to lock me in the car after I got in.... Shocked
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Charles
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PostPosted: Mon Jan 15, 2018 9:26 pm    Post subject: Reply with quote

Failed to work again this evening as I left work but after a good run home it is working again.

I suspect the battery is on its way out so giving it a good charge overnight - and will continue to do so for the rest of the week - and will monitor daily. Looks like I'll be purchasing a new one on Saturday ...
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Charles
Teacher of Chemistry and driver of ALPINAs - not necessarily in that order Wink
B3S Touring (49/116) - been to the moon and now on the way back!
Renault Grand Espace - not mine but the wife's!
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bmw virgin
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PostPosted: Fri Jan 19, 2018 1:24 am    Post subject: Reply with quote

Back in 2011 I had the relays replaced by a guy called Colin Abraham, he works for Diamond Light Source at the Harwell Science and Innovation Campus.

I drove and met him there.....he took the unit into his work to fix them whilst I waited. Charged me 80.

His email address was colin@cabraham.co.uk
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Charles
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PostPosted: Fri Jan 19, 2018 9:45 am    Post subject: Reply with quote

Thanks for the suggestion Colin.

The current situation is that I put the battery on trickle charge for a couple of nights earlier this week and since then it appears to be working fine - so I must assume that low battery voltage can knock out the system.

Whether the battery is on its last legs or not is another question but at least I am now aware of what has happened and (probably) why.
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Charles
Teacher of Chemistry and driver of ALPINAs - not necessarily in that order Wink
B3S Touring (49/116) - been to the moon and now on the way back!
Renault Grand Espace - not mine but the wife's!
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