P16a7 - 2006 z4mr

[MadGus]

Hi folks… posting up my first head-scratcher with my “new to me” car.

With the engine fully warmed up, at highway speed, downshift into 4th and holding on the accelerator at WOT for ~4 seconds or so triggers this code, along with limp mode, the yellow EML light, yellow DSC/traction light and yellow BRAKE light.

I am running Megan racing headers (catless), a tune from Severn (pokeybritches), and an aFE cold air intake.

Troubleshooting to date includes:

Replacement of the two throttle position sensors on the engine (swapped one at a time and tested both on multimeter) - both were good
Replacement of the throttle actuator - original was good
Replacement of the MAF - original was good
Continuity check for the MAF to DME wiring - wiring was good

The error details from INPA and ISTA talk about the MAF reporting ~200mg/stk less than the calculated amount of airflow, and this makes me doubt that the throttle position sensor on the gas pedal would be causing the problem.

Sooooo… that leads me to a partially clogged exhaust. I’m already running catless headers, so that would mean the H-pipe main cats could be clogged ($1800 to replace with manufactured ones from the online stores), the resonator in the X-pipe could be clogged, or the mufflers could be clogged.

Question for the forum is: am I missing anything else that I should be thinking about in the troubleshooting?

Data logs of the airflow (g/s) max out at 160 and never drop to 0… limp mode seems to be triggered around 4800rpm every time.

I’m going to drop the exhaust this weekend and inspect the components with a camera snake… hopefully the problem will be visually evident!

[TRiCC]

Try replacement of the Throttle Position Sensor on the front of the throttle actuator rail, above the oil filter housing. I had this exact problem, replacement of this part with a OEM part fixed it, this was three years ago, havent had a problem with those three lights since, as a suggestion. Good luck!

[MadGus]

Thanks, but I already tried replacing both of them without any success.

[MadGus]

Dropped the exhaust and separated the S/H-pipe with cats from the x-pipe and scoped both with a tiny camera. There's no ratting when I shake either piece, and visibly all four ends of the cats look intact and unclogged. The x-pipe is totally clear, and I can snake the camera through both sides of the entire length of that section.

I also scoped the mufflers, and while the turns inside are too tight for my camera to go all the way through, they look clear from both sides and also don't make any noise when shaken.

Sooooooo...

I'm going to reinstall the exhaust in the morning, and try replacing the accelerator pedal with a factory one that came today... which has the third and final throttle position sensor for the car in it.

If that still throws a code, then I'll use this $32 backpressure gauge that I got from amazon and see what it says. If the backpressure test comes back good, then I guess I'll go back to the stock tune and see if that changes anything.

Open to any other suggestions as well!

[MadGus]

No joy with the exhaust put back on, so I swapped the accelerator pedal and again still getting the code and limp mode.

I can run the engine way above this rpm and vehicle speed in 3rd with no problem… just seems to constantly throw code in 4th.

I attached the freeze frame data from OBDFusion. 49% throttle position doesn’t seem possible with the accelerator floored. That’s confusing to me… might have to look at resetting adaptations, but I thought our cars did that automatically at startup??

Might do the back pressure test later this afternoon, just to confirm what I was inspected with the exhaust taken apart.

[MadGus]

Coded the error out of DME.

[maupineda]

MadGus reviving this. my car threw the code today as I was driving on the highwayand arround 5000 rpms it threw the code 2D51 (P16A7). This is the first time the car does this. All TPS are relatively new. pedal is about 4 years, and the engine sensors are no more than 2.

When you say you coded it out, was it via the remap? Did Josh do anything on your map to adjust for it?

[MadGus]

Sorry, maupineda. Actually, the advice I got from a BMW mechanic on justanswers.com was to have it coded out, but I never actually did that. I have reached out to Josh about coding the error out, but he said there's nothing about the OTS tune that would be causing this... we have been discussing doing some troubleshooting/data logging

What I ended up doing was flashing it back to stock, and I haven't gotten the code since.

2D51 is the code mine throws any time I'm WOT for more that 3-4 seconds in 4th.

Keep me posted if you find anything out, and I will do the same.

[maupineda]

I am mapped too. Josh did my map. Interesting to hear it went away by flashing it back to stock.

My car had not done it until yesterday and I could not reproduce it again. I also have Catless headers with some other mods.

Did it matter the rpm range? I have done WOT pulls 3 and 4th but 4th I could not hit the redline as that is just too much speed.

[MadGus]

Mine seems to throw the code at about 5k rpm in 4th. I have catless headers and a CAI.

[maupineda]

I put the Eventuri filter back on and tested to see if the filter changes was the root cause, but it did it again. So I am a bit clueless and the code does not give much details. Next would be to map it back to OE tune and see. I wonder if the MAF is now misreading as the code suggest it is reading too high flow.

[MadGus]

For mine, flashing back to stock tune made it impossible to trigger code/limp mode. With the OTS tune, I can trigger it with my are CAI or the stock intake.

[maupineda]

Thanks for the feedback!!!

[maupineda]

To document what I find for this issue. this is what ISTA is telling me. It seems that the DME is finding the MAF reads are above the thresholds set in the DME for tool long, apparently 480, I am not sure what are the units here, I am assuming milliseconds. I need to do some data logging to see what units the DME actually reports.

Based on the below it seems the DME would trigger the DTC if the value the MAF reports is not inline with the calculated value for the given engine speed, load, etc. for more than 480ms



Here you can see the value reported v expected.



The above means the vehicle is detecting a lean condition.

[MadGus]

Almost exactly what I'm seeing on my car, but with INPA. I think that the calculated value is actually what the DME is measuring versus the model value (being what is expected... that would indicate we are getting significantly less mg/stk (whatever that unit of measure is) than expected.

I'm assuming this to be the case, based on data logging I have done with the stock tune/map which shows these values more like 10-20 mg/stk apart at the most.

[maupineda]

Thanks!!! I got it wrong as I was seeing it the opposite way. This means there is not enough air to meet the conditions the DME expects. I recall Josh said he has found a way to change torque limit values to find some more horses by allowing the butterflies to open more, our cars do not open the throttle bodies fully, and I can see on the data that the set point value for engine torque is more than what the engine produces (+430NM), I do see the bodies open more than with stock map so maybe that strategy is resulting in a bug with the tune. I was thinking my MAF could be going bad. Will revert back to stock and test. By the way, much of my thoughts above related the tune is pure speculation! Just my logic based on what I know so far.

By the way, the other phantom codes you have, are those your CAT monitors off? Do you have an engine light because of it with the stock map? That will be my problem as I have aftermarket CATs which trigger a light with the stock map.

[MadGus]

With the stock tune, I get P0420 and P0430 consistently, which does throw the SES light, since I am running catless headers.

I have no idea what the 00000 phantom codes are from, but they do consistently show up with Josh’s tune on, and I have not seen them with the stock tune.

[maupineda]

Those are the CAT codes just being masked. I have them too to avoid the SES light.

Did you adapt your secondary cats to have the post cat o2 sensors relocated? I had read that if you put the post cat o2 sensors to the secondary cats they are good enough to avoid a light.

[MadGus]

I just had Josh code my seconday O2 sensors out. I have them located shortly downstream from the primary O2 sensors, all on the catless headers - I went with the Megan Racing ones for $280... couldn't pass that up.