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Central locking and alarm not working after alternator replacement

accordeon

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Accord 04 Type-S 2.4
Hi all,

Yesterday I replaced an alternator and I have disconnected battery to do so. When finished and connected battery back again, central door locking stopped operating with key fob, I am unable to open boot and alarm won't arm up).
I can open driver's door with key (only driver's door opens, other syat shut) and I can open all doors with button on driver's door - all doors open and close no problem.

I have checked all fuses. I thought that key fob may need re-programming but system did not unlock/lock vehicle after four steps, it did not activate programming mode. Same with spare key. I have disconnected battery once again (to reset system) and tried again, no joy.

I had to go to shop and when I got there all of the sudden I could lock the door, open boot and activate the alarm with key fob. When got back home I have had to disconnect battery again, and the problem came back... I have tried disconnecting battery again, etc. nothing. So I left battery disconnected again and wanted to get back to it the next day, but I had to drive to my parents so I connected all again. When got to my parents (5 min drive) locking door system started working again... I have checked it many times, yesterday night and when I got up, to open and close door remotely and it worked fine, alarm was on and indicators were flashing.

But... only one key worked, the spare one (?) the one I have used all the time would not work at all.

And it worked till this morning when I opened car, got inside, put key in and I could hear door locks moving in all door (although all door were opened) and it stopped wotking again.

So summing up:
- I have replaced alternator and to do so I had to disconnect battery
- I can't open lock door, open boot and activate alarm
- I can open driver's door with key (all other door stay closed)
- I can open/close all door with button inside car (driver's door panel)
- system not responding when trying to program keys, looks like it does not go into pogramming mode
- it happened twice after 5 min drive that problem got fixed itself
- this morning when I opened car and put key into ignition I could hear door locks moving and remote door locking system stopped working...no alarm etc.

Could you tell me what I should be looking for please?

Thank you
 
Last edited:
Hi
Mine is a pre facelift tourer and i have disconnected battery on a few occasions for various jobs during spring/summer and didn't experience anything like this.Keys radio etc dont need recoding for example.Cannot in any way think alternator is the cause neither as you report all fine after a few minites motoring when this new part is running.Could be worth checking no wiring has been damaged to door sensors or locks and bonnet/boot tailgate because this will prevent alarm setting.Just retrace your steps inch by inch most probably stumble on the cause
 
Hi
Mine is a pre facelift tourer and i have disconnected battery on a few occasions for various jobs during spring/summer and didn't experience anything like this.Keys radio etc dont need recoding for example.Cannot in any way think alternator is the cause neither as you report all fine after a few minites motoring when this new part is running.Could be worth checking no wiring has been damaged to door sensors or locks and bonnet/boot tailgate because this will prevent alarm setting.Just retrace your steps inch by inch most probably stumble on the cause

Hi, no, I have never had this problem before, although sometimes there was no battery in car for three weeks when I went on holiday.

All door lock sensors seem to be fine - on dashboard I can see when door are closed/opened, that's including boot. If bonnet sensor was faulty, doors would still close, only alarm wouldn't be armed. I don't think it is anything to do with new alternator, I have just mentioned it as I wanted to describe my problem from beginning. Maybe I created some short circuit, doubt it,

If cable was damaged I wouldn't be able to control windows and locks from driver's door control panel inside car. would I? And I wouldn't see that door or boot are opened/closed on dashboard? Is there an easy way to check wires to all doors?
 
All a bit confusing tbh....have you replaced key fob batteries? They will cause erratic function if low/dead.One point i dont understand is when you use key it unlocks driver door only.....that would be a flat or disconnected battery otherwise CL would open/close everything.possible car has developed a locking fault and the recent work you did just coincidence? perhaps someone else here more technically skilled than me can tell you how to test the system
 
All a bit confusing tbh....have you replaced key fob batteries? They will cause erratic function if low/dead.One point i dont understand is when you use key it unlocks driver door only.....that would be a flat or disconnected battery otherwise CL would open/close everything.possible car has developed a locking fault and the recent work you did just coincidence? perhaps someone else here more technically skilled than me can tell you how to test the system

That's what I thought - when opening driver's door with key it should open all door, shouldn't it?
Yes, I have replaced batteries in key fob.
 
To be more interesting I have noticed that driver's automatic window up and down function stopped working correctly - I have to reset power window control unit every time engine is started abut when engine turned off I have to reset it again to make it working again.
 
somethings off somewhere..probably something simple to fix as everything actually works albeit on and off.You could always get honda to look at it....a diagnostic may cost a few quid but you will be able to carry out the repair yourself.Worth considering as you seem to have hit a brick wall
 
I have replaced MFU (door/window switch controls on driver's door) as there is a key fob receiver. I got exactly same part number as mine from eBay and door locking system works ok now, but alarm won't arm - no light on dashboard and indicators won't flash. I can live with that. I must have caused a short circuit somewhere while dis/connecting battery. I have read few people had to replace this master switch unit cause door wouldn't close/open so I thought I will give a try. Thank you
 
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