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Discussion Starter #1 (Edited)
Hello Everyone hope all is well with you all.

I have a 2008 BMW M5 79k Miles that Check Engine light is on. I took it to Auto Zone and the CODE shows P1515 (Electronic Throttle System Throttle Position)
Few things I've noticed. Sometimes when im stoped after driving at idle the RPM moves little up and down for a little bit then wont do it again.

Also somebody told me that the P1515 is for the battery. And ever since I had the car (6 months) everytime I get in the car and start it my clock resets to -:- then I have to set time again once I shut it off and turn it back on resets again. If i want to listen to music with my car off after 10 seconds of the car being off i get the battery picture on and the systen shuts off completly so it doesnt drain the battery off.


I have owned over 7 ///M's and first time on a M5 and never had a problem with any one of them but the current M5 which I already replaced 1 injector ($1,600). I am far away from even calling myself an expert but i thought since this is the best & biggest M5 forum somebody would be able to help me. So If you know anything please share with me since I do not trust BMW service department because last time they kept telling me my car all kinds of stuff wrong cause they wanted my money, i kept refusing the work then finally they came back and told me they found the real problem which was the injector at that time. Ever since the car been great but for the past week started doing that and also if im at low speeds lower then 2k RPM car feels like its asking to downshift since it kind of feels struggling a little...just a little but anything over 2k RPM car drives like a dream.

EDIT******OnBoard Computer says "Increased Emmissions"

Thank You
 

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Have you done the obvious and have the battery and maybe alternator checked?

I learned that you can't take the DTC tooo seriously if you suspect electrical issues.
 

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Discussion Starter #3
Have you done the obvious and have the battery and maybe alternator checked?

I learned that you can't take the DTC tooo seriously if you suspect electrical issues.


I have not done anything yet since I wanted some advise from some of you guys here. My altenator should be good since it charges my bettery because i drive it twice a week which is usually all day. But I think I might have a bad battery or a battery that's going bed and can't hold any juice unless the car it's on. I called BMW and they said I might have to replace the throttle system or whatever or could just be a sensor but again that's how they got me in the door last time then droped the ladder on me.
 

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I'd start with battery getting checked out /replaced at an indy shop that knows BMWs. You're supposed to "register" the battery when it's replaced which you can't do without the proper diagnostic software.

I think we agree the battery is dying anyway so start with something you have to do. Have them clear the fault in the DME for the TPS sensor and see if it comes back.
 

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Discussion Starter #5
I'd start with battery getting checked out /replaced at an indy shop that knows BMWs. You're supposed to "register" the battery when it's replaced which you can't do without the proper diagnostic software.

I think we agree the battery is dying anyway so start with something you have to do. Have them clear the fault in the DME for the TPS sensor and see if it comes back.
First I want to thank you for advice.
Now do you think that all the things I've listed could be cause of the battery including the rough idle while driving low speeds in high gear under 2k RPM?
I hope it's just the battery so I dont have to spend almost 2k on it again
 

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A bad battery will undoubtedly cause idle issues.

As the battery voltage dips for whatever reason, the IBS (Intelligent Battery System) sees the current draw and voltage output and tells the DME (ECU) there is a voltage issue. DME tries to shed load (telling other electronic modules in the car to turn things off) and/or raise alternator output.

- If load is shed --> less electrical load on system --> less current draw from alternator --> less countertorque on alternator --> engine speeds up slightly
- If alternator output is increased, the opposite happens. More alternator output --> more countertorque applied to engine --> engine slows slightly

As the system tries to figure it all out, your idle may wander.

Also, alternator regulator can be bad, causing output to be high or low. While it may be sufficient to charge the battery, it isn't what the IBS and DME are calibrated for and it has a harder time calculating load changes.

Edit: But based on your OP about engine off stereo listening, I would replace the battery first. New battery registration is key. It may not actually prolong the life of the battery, but it can certainly shorten it.
 

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Discussion Starter #7
A bad battery will undoubtedly cause idle issues.

As the battery voltage dips for whatever reason, the IBS (Intelligent Battery System) sees the current draw and voltage output and tells the DME (ECU) there is a voltage issue. DME tries to shed load (telling other electronic modules in the car to turn things off) and/or raise alternator output.

- If load is shed --> less electrical load on system --> less current draw from alternator --> less countertorque on alternator --> engine speeds up slightly
- If alternator output is increased, the opposite happens. More alternator output --> more countertorque applied to engine --> engine slows slightly

As the system tries to figure it all out, your idle may wander.

Also, alternator regulator can be bad, causing output to be high or low. While it may be sufficient to charge the battery, it isn't what the IBS and DME are calibrated for and it has a harder time calculating load changes.

Edit: But based on your OP about engine off stereo listening, I would replace the battery first. New battery registration is key. It may not actually prolong the life of the battery, but it can certainly shorten it.
That makes sense. Onboard computer says Emmisions Increased
 

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A bad battery will undoubtedly cause idle issues.

As the battery voltage dips for whatever reason, the IBS (Intelligent Battery System) sees the current draw and voltage output and tells the DME (ECU) there is a voltage issue. DME tries to shed load (telling other electronic modules in the car to turn things off) and/or raise alternator output.

- If load is shed --> less electrical load on system --> less current draw from alternator --> less countertorque on alternator --> engine speeds up slightly
- If alternator output is increased, the opposite happens. More alternator output --> more countertorque applied to engine --> engine slows slightly

As the system tries to figure it all out, your idle may wander.

Also, alternator regulator can be bad, causing output to be high or low. While it may be sufficient to charge the battery, it isn't what the IBS and DME are calibrated for and it has a harder time calculating load changes.

Edit: But based on your OP about engine off stereo listening, I would replace the battery first. New battery registration is key. It may not actually prolong the life of the battery, but it can certainly shorten it.

Jcolly,


you mentioned in a previous thread that the IBS tells the alternator to turn on or off correct? If i disconnect the IBS would the alternator still supply power to recharge the battery ?


Part number for IBS i found is :
61217620566




<table id="partsList" data-partlink="/bmw/enUS/part?id=EH93-USA-08-2006-E63-BMW-M6&mg=61&sg=10&diagId=61_1885&q="><tbody><tr class="r1 pos01"><td>
</td></tr></tbody></table>
 

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Jcolly,


you mentioned in a previous thread that the IBS tells the alternator to turn on or off correct? If i disconnect the IBS would the alternator still supply power to recharge the battery ?


Part number for IBS i found is :
61217620566




<table id="partsList" data-partlink="/bmw/enUS/part?id=EH93-USA-08-2006-E63-BMW-M6&mg=61&sg=10&diagId=61_1885&q="><tbody><tr class="r1 pos01"><td>
</td></tr></tbody></table>
It will charge your battery even if IBS is disconnected.
 

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Did you replace your car with the same battery as before?
Was it the same agm rating as the oem battery?
Or is the new one a higher agm rating?

Check the voltage of your car when it's fluctuating.

Check your VO list to make sure it has something like -A080 or -A090.

I had a similar situation and it wasn't my alternator but the coding registration for the new wasn't done properly.

Read the data for your CAS in NCSExpert. Open the .trc file in notepad and Control F to find KLASSE_BATTERIE then look what it says. It should be either 90ah_agm or 80ah_agm or higher depending on your new battery. Your VO MUST correspond to either.

My VO had -A090 when my CAS was saying 80ah_agm. So I changed it to 90ah_agm saved the .man file and after that all issues disppeared.

Before I figured all that out I replaced the thermostat because of a thermostat stuck code Fluctuating idle just as yours, alternator codes I also changed the gas pedal lol precat 02 sensors. Was about to buy the pedal position sensor then I found a thread on here that helped me. Kudos the that guy. I wanna buy him a beer lol.

Hope that helps
 

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Considering the issues you mentioned and mileage, your battery needs to be replaced for starters. Like jcolley said, make sure to have battery properly registered especially if the specs of the battery are not the same as you can cause voltage issues if not properly registered and possibly cause harm to other electronics. These cars have a lot of electronics and these batteries take quite a beating, but your clock should not be resetting each drive indicating it is no longer holding a charge correctly.
 

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Brand new battery from BMW installed and coded. No change.



Could there be a fuse or relay between the alternator and the battery to prevent it from charging ?



I found this relay -
<table id="partsList" data-partlink="/bmw/enUS/part?id=EH93-USA-08-2006-E63-BMW-M6&mg=61&sg=36&diagId=61_4163&q="><tbody><tr class="r1 pos01 poshl posselect"><td>61366901469</td></tr></tbody></table> which may be linked to the alternator not charging the battery. Thoughts ?
 

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Did you replace your car with the same battery as before?
Was it the same agm rating as the oem battery?
Or is the new one a higher agm rating?

Check the voltage of your car when it's fluctuating.

Check your VO list to make sure it has something like -A080 or -A090.

I had a similar situation and it wasn't my alternator but the coding registration for the new wasn't done properly.

Read the data for your CAS in NCSExpert. Open the .trc file in notepad and Control F to find KLASSE_BATTERIE then look what it says. It should be either 90ah_agm or 80ah_agm or higher depending on your new battery. Your VO MUST correspond to either.

My VO had -A090 when my CAS was saying 80ah_agm. So I changed it to 90ah_agm saved the .man file and after that all issues disppeared.

Before I figured all that out I replaced the thermostat because of a thermostat stuck code Fluctuating idle just as yours, alternator codes I also changed the gas pedal lol precat 02 sensors. Was about to buy the pedal position sensor then I found a thread on here that helped me. Kudos the that guy. I wanna buy him a beer lol.

Hope that helps



So what ended up being your issue? All those other parts you changed did not need replacement ?
 
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