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Discussion Starter #1
Hi, bit of a long post but here goes...

The car had the timing chains changed and walnut blading for the swirl flaps. This was causing bad performance and harsh gear changes. Before it was done we had not had any issues with the car and before we had it done we had. It scanned for gearbox faults as if it had any the car would have been auctioned! The scan came back clear re gearbox faults.

The car was perfect after for about a week and then 1 morning it came up on I drive saying transmission fault drive moderately. We took it back to the garage as we thought it may be fluid level incorrect or a connector not put back correctly as the engine and gearbox had to come out for the work. They checked everything and said it was showing clutch slip fault and 400626 turbine speed sensor short circuit to ground or open circuit and it needed a metatronix? As this was an internal failure. I said I didn't believe it as it was so coincidental that it happened after the work they had done and also after a few seconds driving the warning went off and a restart took it out of limp mode. They then said it could be the adaptions or just disturbing it and cleared the faults and said it may never happen again.

The next morning it happened again so it went back in and they said it had the same faults and it would be better if we took it to a gearbox specialist which they recommended as they would have more knowledge and if it was something they had done they would pay for it.

The car was checked over and they said that it wasn't an internal failure but could just be the start of wear due to mileage.

We took it away and the next day the same thing. This time I took it to a local mechanic I use just to check the fault codes. He checked and it had loads of faults, most of which stated low voltage, he drop tested the battery and it was showing as bad. This made me think that the garage that dome the work initially asked if they could keep the car overnight once they had done it as the battery was only 30% charged to see if an overnight charge sorted it or if it was did. They said it was fine after a charge. We were now on a Friday and bmw didn't have a battery in stock.

The next day it came up with the transmission fault in the morning as normal, about an hour later it lit up like a Christmas tree saying battery charging fault. Breakdown came out and said the alternator wasn't giving anything out so we also asked if this could cause the transmission fault and he said it is 1 of the first things to play up on these cars if voltage is low. I thought we had nailed the problem now and had an alternator fitted. Once it was fitted the warnings for charging etc went out. Alas in the morning the transmission fault was on again so I had the battery tested and it was showing good voltage but still saying it was bad. Now I also had an alternator fail in my A8 Audi and as the battery is coded was told that it wouldn't charge correctly unless it was replaced but coding the existing battery as a replacement normally worked, which it did. Thinking about this a wondered if it was the same in this case so I ordered a Carly adapter and checked the battery stats, it was the original battery so could be dead but registered it as a new battery as I had nothing to loose.

The next morning and the same problem but I carried on for another week or so incase it needed time to fully charge but no, I read the battery stats again and it was showing 2 hours of charge between 70-85% and the rest 85-100. Drop tested it again and it still showed bad so I got a new battery from bmw, fitted it and the next morning the fault shows again! Checked the stats and shockingly it showed 4 hours 70-85% and 13 85-100%. I must admit I haven't had the new battery drop tested but I find it unlikely the new battery is a dud so could this speed sensor fault be draining the battery and where would I check? I'm convinced it is just going to be something silly such as a dirty connector or a break in the loom somewhere but does anyone have any idea where to start or a way to check what is draining it please? Many thanks
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