So having a bit of a problem with my XT660Z, it has the dreaded fault code 53. I have read as many posts on the forum as I could about it but still can't get it sorted. I havr checked the ECU connections, cleaned the immobiliser connection and checked for battery voltage on the loom side of that connector (there is voltage there) leading me to suspect a faulty immobiliser receiver... my question is really is there a definitive way to confirm this and if the receiver is faulty do I have much in the way of options? From what I can see the part I would need is just shy of �400.00 from Yamaha Thanks for any help in advance Sean

Have you tried the other key?

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Yeah, that was one of the first things I tried... also tried to use the red key to re-register the keys the other day as well but it doesn't seem to recognise it either but I know the procedure for that can be a bit fiddly so it is possible that I didn't quite get it right.

One thing that occurred to me last night, how does the receiver communicate with the ECU - is it via a wire back through the loom?

Also whether any of this is relevant or not I don't know but I'll give the full story too. The problems started after a flat battery one morning (it had been a cold night so I put it down to that), charged the battery and put it back in and all seemed fine for a couple of days. Then I started getting an intermittent Code 53, it seemed to be solved various ways, moving the handle bars, tightening battery terminals but a few days later those little tricks stopped working.

Checked battery voltage again and it had gone low, charged it and put it back in and the bike started, checked the reg / rec charging voltage across the terminals and it was the same at 0 rpm as at 5000 rpm (that was the last time I managed to start the bike). After that the battery didn't seem to be able to hold any charge, even after being fully charged it was dropping to c. 12.40V by the time I could get it to the bike. Changed battery and reg / rec for new haven't actually been able to start the bike to test it.