Hi

I've had P0234 codes (without getting a check engine light, it was just random scanning once every days...)

My engine is running really fine, but I was just wondering was that means?

Is there a certain PSI level which gives this overboost condition?

What does "overboost conditions" make? (ECU readjusts timing??)

Thanks for any clear ups!

 

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I don’t have that code number listed in any of my resources as Mini specific. A few times my car has generated an erroneous non-Mini code without a light and has cleared it on its own.

What scan tool are you using and how did you know it was an over-boost code?

 

The factory scanner (or equivalent ) would give you the text of the fault code, along with the conditions under which it was set. The TMAP sensor has an upper limit for boost readings, and when exceeded, it can set that fault.

 

I have read that the TMAP sensor has a limit of a bit over 18psi on the top end. If you had a 19% or better there is a chance you will be getting into this territory, and if the ECU sees it it can be 'aware' of it without it being a candidate for the MIL and throwing an 'official' code. Not sure what the ECU will do when presented with this reading, and I am also not sure exactly what the TMAP does at that pressure level. Does it hit a brick wall and register no more boost, does it become non-linear, or is there a bit more range available that's not officially spec'd which the system uses at the ragged edge of boost?

 

so how do the twincharge cars get pass this problem surely they run more than 18 psi?

 

They dont im sure.....GreatBear is right...........I get this all the time when i hit redline..( im boosting abt 16-18psi )...Nothing will happen ( hasnt so far nor changed anything on mine and i get a code every other day )

It goes away after 4-5 key cycles.

 

Thank you for the answers guys!

What's really strange is that this code doesn't throw on my check engine light. I don't feel any difference when the code is on... I only know it by scanning my ECU with my scanner.

I'm using a 15% pulley and saw 18+lbs of boost twice on my boost gauge. (at redline.. 7200rpm on my car)

So, I shouldn't be worried about this code, and just erase it?

 

I just looked in my data base and couldnt find this code.

I pulled a code last nite but i forgot the #....i dont remember it being the one your tellin us but i know mine was for the samething. it was boost singal out of range or something. ill check it again when i get a chance....It went back on right when i left the shop after resetting the codes.

 

There are many fault codes that will not turn on the MIL. Only emissions-related ones turn on the MIL. I'd clear it and see if it comes back.

 

Mine is doing that now with my added boost. Is there anyway to fix/upgrade the sensor?

 

Nope. If you had a sensor that delivered a different voltage range for a given boost value, you'd need to have a special chip made for the DME to handle it.

 

Great! thanks a lot guys!

Andy, as usual, you impress me with your knowledge about all those tech details!

 

One point I haven’t seen addressed is can you treat a non-Mini code as if it’s valid? Has the event truly occurred that triggered the code? The erroneous code that my car has generated is for cruise control yet, I don’t have cruise control.

 

What's the actual code you have? Copy and paste and either post or email it to me.

 

According to the Bentley Manual, pg. 130-14/15, the Cooper T-Map Sensor has a maximum pressure range of 120 kpa (17.4 psi), while the Cooper S T-Map Sensor has a maximum pressure range of 250 kpa (36.2 psi)...

So it makes sense why some guys are getting some CEL when some boost is reached.. ( 17-19 psi).. I guess it's because the DME does not like it when it sees a boost over some "factory limit" even though our T-Map sensor can actually handle up to 36 psi.. Is this right?

///Gilbert

 

Please re-read what you wrote sir.........If the S has a max limit of 36psi and everyone just stated #'s around 15-18psi, how can we be out of range and throw a CEL......Bentley Manuals are never accurate from what ALL my customers always tell me.

 

I will assume that Bentley is almost pretty accurate... But of course discrepencies will happen due to having their manuals cover multiple years.. I use Bentley for all my BMWs so I can assume that they do research all that info in their manuals properly.. I think they have sold enough manuals throughout the years to be able to afford all that reasearch.. I'm sure they get the info straight from BMW itself..

Here's what I mean.. The T-MAP sensor is able to handle reading between 0-36 psi... But the DME is programmed to throw a CEL if an overboost of 17-19 psi... Our cars come stock w/ 11 psi from the factory right? So if your car is running 17-19 psi, something must be wrong, so a code of P0234 gets recorded, to inform your dealer/mechanic that there is something not right.... So in other words, the DME uses the T-MAP sensor to check if your car is w/in the factory boost limit of 11-16 (I guess to also make sure P0234 doesn't come out w/ the JCW upgrade)...

To fix this problem, it seems that the only thing needed is to raise the boost limit in the DME... The T-MAP sensor doesn't need to be changed since it can handle up to 36 psi....

///Gilbert



///Gilbert

 

I think you're mostly right (about the boost limits and such) but don't forget that the 0-36 psi is ABSOLUTE. So, since ambient air is about 14.7 psi, that would correspond to boost of about 21.3 psi. Plenty of headroom for most modders, but not for the wilder turbo'ed cars.

 

Dont confuse gauge pressure (psig) with absolute pressure (psia).

The MAP/TMAP sensors read absolute pressure, i.e. starting at a perfect vacuum and not taking into consideration atmospheric pressure (there's a reason why they are called manifold absolute pressure sensors). Gauge pressure, which is the method most of us are used to seeing, measures pressure in reference to atmospheric pressure. For example, a totally flat tire will read 0psig, even though it actually has about 14.7 pounds of air in it at sea level. Assuming that tire has no leaks, you can take it with you to the top of Mount Everest and check it again, and you will be able to read a few pounds of air in it with the same gauge you tested it with at the beach. This happened because you took the tire with 14.7psi of air in it which was equal to the ambient air pressure at the beach and now have it in an environment where there is less ambient air pressure relative to what is inside the tire.

A typical gauge, be it an oil pressure gauge, boost gauge, tire gauge, etc references it's readings against the surrounding air pressure simply because of the way they are constructed. Change the surrounding air pressure by an appreciable amount and you have actually changed the calibration of the gauge. It's for this reason that cars like the MINI used a sensor referenced to absolute pressure. The minute differences in manifold pressure that the ECU sees and adjusts the fuel ratio against would be thrown a huge curve if the sensor were to measure and reference to atmospheric. A drive at the beach would be normal, but by the time you've hit the Rocky Mountains and the thinner air there, the ECU would be seeing uncorrected air pressures and metering in a lot more fuel than necessary. The MAP/TMAP sensors are essentially made with a small chamber inside with a near perfect vacuum inside. A diaphragm separates this chamber from the measuring port, and an electronic circuit measures the pressure exerted on this diaphragm. If you were to take a MAP sensor with you to the beach along with a device to connect to it and show you what it's reading, you would see the 14.7 psi (give or take depending on the weather) of air pressure pressing against that chamber with the total vacuum in it. Shake the sand off the sensor and the readout and take it with you to Everest, and you'll see the pressure considerably lower. If you had the chance to blow the snow off your contraption and take it into space with you, you will see it reading zero (and wish you were back at the beach).

Just a bit of science along with some silliness.

 

Thanks for the write up.

 

Greatbear = The 'Splainer

 

:impatient uhhh....what were we talkin abt?


Damn your good ! If you ever move to Long Island you got a job waiting for you.

 

I wonder is this something a MTH remap can fix?

maybe move the upper limit to somewhere around 20psi,
that would sort the problem.
maybe Volker can pitch in on this one?