2003 Z4 3.0 codes P1515

ph001 · Post by **ph001** » Thu Feb 20, 2020 6:42 pm

I think OP has replaced the entire throttle body though. Assuming he bought oem new and hasn’t fitted a faulty part!

Stevepj · Post by **Stevepj** » Thu Feb 20, 2020 9:28 pm

The 2774 code relates to a CAN engine cut off time fault and has been known to be linked to fuel pump failure, which may be worth investigating.
Most Internet searches list P1515 as being related to the throttle position in one way or another, but the one I've linked below also points to a CAN fault and engine time plausibility issues.

https://www.autocodes.com/p1515_bmw.html

The Z4 use the dashboard as the meeting point for all the systems which could be why the dash was identified earlier if it wasn't receiving all the right inputs.

I had an example of how hard to trace these faults are with my son's Focus ST a few weeks ago. The car was throwing all sorts of codes relating to emissions, fuel pressure, CAN US, active suspension, traction control and more I can't remember. It would keep going into limp, the engine service light and EML were lit, auto stop start wouldn't operate and the hatchback would randomly unlock.
Ford couldn't identify the problem and their best advice was to clear the codes, drive it for a week and bring it back to check for any faults.
We kept looking and eventually found the cause of all these issues. The car had been in for a recall on a clip holding the fuel pressure sensor in place and whoever replaced the clip also fitted a cable tie around the sensors wiring plug. The cable tie cut through the insulation on two of the wire and they were intermittently shorting together and causing havoc in the CANBUS signal. Removed the cable tie, separated the wires and everything returned to normal.

SystemLord0 · Post by **SystemLord0** » Fri Feb 21, 2020 12:54 am

Thanks for all the pointers guys!

For a quick review:
- Throttle body has been changed to a new one so that is out of the equation
- Idle Air control valve i removed and cleaned and the little flaps moves and moved freely.
- Accelerator pedal had been replaced for testing and didn't resolve the issue
- Battery seems fine; is new and the P1515 issue has been around for a long time now and getting worse over the years. Does not seem to travel with the battery and alternator seems to be fine.

I went over your comments and came up with the following action plan to continue:

1) New DISA valve is coming in tomorrow and i will replace it (already payed for it) so this would eliminate the DISA valve.
2) I will inspect the MAF sensor and clean it with MAF cleaner...maybe its been building a deposit on it even thou everything in the air system seems somewhat clean. MAF: Measure Ohm/Voltage; Clean; Measure and compare. Then test the whole system to see if that fixes anything.
3) If the DISA and MAF wont give me results i will have to start looking closer into the connectors and their wiring. I will start with the throttle body and accelerator pedal connectors and wiring. Does anyone have or know a source where i can get wiring diagrams? This way i could check my wires from source to source and make sure they are not intermittent etc.
4) If i cant get anywhere with the wiring i will try to get a smoke check done to check for any leaks in the intake system. I don't have a smoke making apparatus so i would have to get one so this is why i have moved this further down the line.

My OBDII can read live data; i will check on what it can read but i am sure i saw options for:
Mass Air Flow Rate lb/min (Can i use this to check my MAF sensor to compare to values someone else is getting?)
Absolute Throttle Position
Fuel Trim Bank 2 and 1 (Long and Short Term)

I am not sure what i would be looking for thou.

Will be a busy weekend; ill report back on each steps to see if we learn anything new.

Thanks again!

SystemLord0 · Post by **SystemLord0** » Fri Feb 21, 2020 2:38 am

I did not by the BMW OEM throttle body; i bought the VDO replacement. It had decent reviews and was a bit cheaper at 250 vs 500 from BMW.
https://www.fcpeuro.com/products/bmw-th ... 7502445#qa
Should i try OEM instead?

Other than than the fact that i use Chevron gas (sometimes Shell) and have used fuel and ejector cleaner (maybe once year) i have no info on the fuel pump. Engine seems to be getting gas and does not seem to be sputtering etc but i will look up if there is a way to some info from the pump. Full pressure gauge at the engine etc.

That being sad one the only other code is that 2774 (Engine cut off time) so maybe that does have something to do with it. For now ill try my stems from above and see where we end up before heading to the pump.

SystemLord0 · Post by **SystemLord0** » Sun Feb 23, 2020 1:41 am

Hi everyone; thanks for sticking around and helping me get my car going again.

I have a few important updates;
I started looking into the live data from my OBDII reader and started mapping RPM (PID 01 0C); Mass Air Flow (PID 01 10) & Absolute throttle position (PID: 01 11 ). From the get go i noticed that the throttle position info did not always perfectly follow my pedal movements but its hard to notice when looking at the hand held reader so i exported the data to excel. I was expecting the RPM, MAF and ATP to be behaving very similarly; press on gas = increase airflow = rpm increase.
However it seems like the ATP has some readings that are not consistent with the engine behavior nor gas pedal moment. The engine behaves as it should based on my foot moment but the ATP reading does not match.
I have attached a PDF (with notes) and my source data with graph in excel. The excel graph is nice too look at but PDF does how it too.
I was not sure if the ATP reading is just not perfect from the OBDII so i did the same data output on my brothers 2005 Subaru and his behaved exactly as expected with all three values moving together and the ATP registering also slight foot moments.

I think this is good evidence to support that the P1515 is related to the throttle system somehow and this area is worth looking into in more detailed. For some reason this Absolute Throttle Position % is not consistent with what is commanded via the foot pedal. I think the location where the ATP% (PID 01 11) is measured or calculated from is the source of the error and P code.

The gas pedal seems to be sending the correct position to the car since the physical response from the car feels "right" and the MAF rate and RPM seems to be responding consistent. However whatever measured the ATP or values used to calculate the ATP are incorrect.

I am not sure if the gas pedal uses a poti of some sorts to output position because i could read these values to confirm its working correctly. If its digital it would be harder.....

-I changed the TB already so that seems to be unlikely bad again.
-The DISA valve was changed today; there where some slight defects on the flap seals and i was hoping replacing it would solve my issues but it seems to not be the primary cause at least.
-MAF sensor was cleaned to day (with MAF cleaner) and it looked in good shape and it seems to be reading mass air flow correctly based on RPM increase. But i have not measured it yet (Ohm, voltage etc).

Hopefully this information will be helpful to figure out what to look at next / possible causes.
Could it be that the computer that's calculating the ATP is faulty? Where is that done?

PS: I noticed i cant upload EXCEL or PDF files.... i uploaded JPGs of the graphs for now but i will see if i can figure out how to upload files online somewhere and share the URL or i can PM the files if needed.

Manuel

SystemLord0 · Post by **SystemLord0** » Sun Feb 23, 2020 2:10 am

Before going home and waiting for more help i did another quick test run with the live data output.
I put the car in neutral and slowly increased RPM from idle to 4400 while mapping ATP RPM MAF.
Results in graph image attached; defiantly something very wrong with the ATP% calculations.

Will be back tomorrow to see what to tackle next.

SystemLord0 · Post by **SystemLord0** » Sat Mar 07, 2020 3:23 am

Hey guys;
Here is the latest update; will need some new ideas since i am still having the same problem even with my latest tests.

I am going off the assumption that my ATP is not being sent/receive correctly at this point.

I ended up buying a new BMW cable harness connector for the throttle body to make sure that its connected well and its not just a worn out connector pin (cleaning didn't help). I was able to buy a pigtale type to spice into the existing wire harness. https://www.pelicanparts.com/More_Info/ ... VSVSI=BE85 At first i was hoping i could spice the wire inside the engine cable harness distribution box but it was too complicated so i cut the current connector about 0.5" from the connector and soldered the new pigtale on. (Shrink tube over each wire plus a big shrink tube over the ribbed sleeve.) I figured i would start with just replacing the connector instead of going with the full cable harness replacement which is very similar to this part (https://www.eeuroparts.com/Parts/179245 ... P2EALw_wcB).

Did this connector replacement today but i am getting the same ATP readings so i don't think that was it.

I also bought the Haynes repair manual which has a wire diagram which seems to indicate that the ATP is wired directly to the DME (Digital motor electronics control unit). It has some description on how the wires are done including the internal of the ATP.

The only next steps i can think off are to measure the Supply voltage (must be 12, 6, 5, 3 or so i am guessing) to the ATP and the return (i am guessing its a ground) The SIG should change depending where the physical location is of the ATP and i am guessing this is whats being detected wrong. Its like a potentiometer and should change the voltage based on the physical flap position i think.

I am going off the assumption that the Throttle actuator motor is working correctly since the car seems to perform normally and the RPM follow my gas pedal moments.
(See attached image of wire diagram.)

I am wondering if anyone can send me their ATP vs RPM and MAF data; anyone have an input on my assumption that it’s not the gas pedal or connector since my RPM seem to be changing in correlation to my physical moments.

I would imagine if the DME would be defective i would have more errors but could it be that this is causing the problem?

I’ll try to splice into the ATP wiring over the weekend and get some voltage readings so see what kind of ground/power and sig voltages i am getting.

Any input would be much appreciated.

Thank you!

Manuel

ph001 · Post by **ph001** » Sat Mar 07, 2020 1:36 pm

Great work you have done trying to diagnose this. I think you are correct in the the next thing to do is look at another M54 to see what the live data looks like. I would have done this for you but I have N52 unfortunately. Maybe another member can help? You probably need to describe exactly what software you are using and how to log.

Venkov · Post by **Venkov** » Sat Jan 29, 2022 9:06 pm

Hello everyone! Can you reply if were able to resolve the issue? I have M54 with the same trouble code and is becoming a PITA with a constant low rpm surging. Thanks

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