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Steve, BMW Expert
Category: BMW
Satisfied Customers: 25230
Experience:  BMW Expert
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I have an Alpina B10 V8 1999 E39 double vanos , my battery

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Hi I have an Alpina B10 V8 1999 E39 double vanos , my battery went flat a couple of times as I wasn't using the car and I moved the car about 6 miles from home to store , the battery went flat again , I went up to the car a couple of months later and jump started it off my other car , I was running really bad , I put fresh fuel in and injector cleaner but no change , I changed the spark plugs and no change .I was told the battery has to be 100% good and charged so I put it on my ring smart charger and tested it to be 85% good with the amp output , its an 850 battery , I put it back on the car and it ran better but still like its running on 6 cylinders , I've run it for about 15 minutes at above 2000 rpm and the left bank cat was glowing but the right bank wasn't ? Do I need to have fault codes reset before it will run correct ? Also the engine management light is on but then after 10-20 seconds starts to flash ? Why ?
what faults are logged in the car's computer fault memory?
Customer: replied 2 years ago.

How do I find that out ?

by having the faults scanned from the car with a diagnostic scan tool
Customer: replied 2 years ago.
£15 for that answer ! Well I could have had that done anywhere and already knew that much , what I want to know is do they need to be reset so the ecu will go back to normal and is jump starting off another car why it happened ? Does this sometimes happen this way ? It was perfect when I parked it up , I know a sensor could have gone down but to misfire that bad and then charge the battery and it runs on more cylinders now is odd , let alone the hot left bank cat . Can I buy a reset tool or do I have to plug it into a laptop therefore better take it to a specialist bmw place
all I did was ask what faults were stored, I did not answer anything or imply that was an answer.if you have not had the faults read out, which is the absolute first step any time the engine light comes on, then what question is it that you would like answered about this?
Customer: replied 2 years ago.
If the low voltage causes the ecu to be confused will a reset sort it out if there are no actual faults ?

the answer to your question is no, low voltage will not cause the ecu to become confused.

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thank you

Customer: replied 2 years ago.
Really ? This is what I was told by a bmw specialist and wanted a second opinion so I could maybe buy a reset tool , I have a service light resetter but not a fault code and reset tool

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you can reset the ecu by unhooking the car battery for an hour.

low voltage can cause auxiliary system failures and commonly does, but typically the engine runs fine and does not misfire just because there is low voltage

a simple low battery does not cause low voltage, as long as the alternator isn't faulty (nothing has been shared to suggest it is) then the car should run fine.

Please do not forget to CLICK ON a positive rating

if there are no additional questions, please kindly CLICK ON a positive rating
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