Hi All,

I'm desperately hoping somebody can help me. I have a R56 Cooper S (UK right hand drive) and I​​​​​​ have two consistent errors which even if cleared when the engine isn’t running, will reappear as soon as you turn the ignition on:

There are 2 error codes which I can’t seem to shake, these are:

2EF2 Intake Air Temp
289D Boost Pressure

I sometimes get a post-cat o2 sensor error too which may present itself when I bring the car in. I suspect all of these are false positives and there is really a leak / wiring issue somewhere but you may tell me differently.

What I’ve done / know has been done so far:

Traced the IAT back to the ECU and noted the following:

Middle (red connector on ECU) with ohms (20k)
• Pin13 goes to the white wire on the IAT ohms reading 0.00
• Pin 23 goes to the yellow wire on the IAT ohms reading 0.03
• Pin 44 goes to the orange wire on the IAT ohms reading 0.05/0.06
• Pin 45 goes to orange wire of MAP sensor (ohms not noted but there was continuity for all of these)
• Pin 43 goes to white wire of MAP sensor
• Pin 21 goes to yellow wire of MAP sensor

Blue connector (I haven’t noted which one but I’m sure they are marked differently):

• Pin on Row 4, B goes to Blue wire on IAT ohms reading of 0.00

The following have been replaced:

• MAP Sensor
• IAT Sensor (this doesn’t seem to fit into the hole correctly but I don’t think there is a leak. According to a cheap diagnostic tool and Bluetooth OBD there is a reading of -40 degrees at all times but with not having genuine BMW diag I’m not sure if this is correct) I’m not ruling out that the new sensor isn’t faulty although it’s highly doubtful.
• Wastegate valve actuator
• Water Temperature Sensor
• Both O2 Sensors (the post cat sensor has a slight nick in the wiring although continuity tests OK)
• Thermostat Housing

Other Observations:

The car doesn’t idle quite right and is hesitant / hunts when holding your foot steady around 2-3k RPM particularly in 3rd gear. It’s almost as if it gets a sudden rush of fuel / acceleration despite holding your foot in the same position.

The issues seemed to manifest around 50-100 miles after the previous owner removed the sports cat Milltek / JCW combination exhaust and put the standard exhaust back on.

It loses oil and needs to be topped up around every 500 miles, I suspect the valve cover might be leaking and gather that oil loss is quite common with these but perhaps you could advise?

Things I haven’t been able to check properly:

Vacuum / Exhaust leak
Turbo wastegate
High pressure fuel pump (although the car fires up fine and I’m told hesitant starting is the main symptom?)

The turbo feels OK and the engine seems strong enough – it has only done 60k miles or so.

I’ve done a basic leak test just by spraying carb cleaner around the engine bay but I don’t know if the sensors would compensate for this - is there a better test I can do?

Hope the above makes sense and I’m truly hoping you might just know what it is straight away but it’s certainly baffling me and I’ve repaired plenty of vehicles in the past!

Thank you in advance

Ben

 

Forgot to mention that generic codes are P0112 and P0238 if that helps?

Cheers

 

P0112 is Intake Air Temperature Sensor 1 Circuit Low.
P0238 is Turbocharger Boost Sensor A Circuit High.

Probably a wiring or connector problem.

You didn't mention which year, but I'm guessing it is pre-2011 and has the N14 engine. You may be losing a lot of oil through the PCV system, there is an updated valve cover available that helps.

 

Thanks for the reply, really appreciate you looking at it.

Just tested resistance on the IAT sensor and not sure if these are numerically correct but tested all pin combinations and I had readings from two which changed with heat, I did 3 tests, one just unplugged from the car, one next to a warm engine (to test on heat change) and one in the garage.

Pin 1 + 3: 5.7, 4.6 then 5.3
Pin 3 + 4: 1.99, 0.3 then 1.4

The other pins didn't change with heat and I had two IAT sensors both with similar results so either they're both faulty or I'm suspecting ECU now.

Also checked all the wires back to ECU again for a sanity check and all tested fine.

Are ECU issues common on these or unheard of?

 

ECU problems are not common, but not unheard of. Yeah I know, that wasn't helpful.

My gut feeling is that the two codes have a common cause, but I can't say what it might be. I would have to study the Bentley manual to come up with ideas. Look up the wiring diagram either in the Bentely manual or on newtis.info and see if that leads anywhere.

 

Was this ever resolved? What was the fix? I have identical symptoms and codes, I am leaning towards DME replacement.

Thanks

 

I bought a lemon Swiss Mini last seen it 2020 & put a oem air filter in i bought it2½ months ago 2025 last owner Rapped the poor boy. First time swiss mini seen it they put. Miltec cat back, induction, coil overs & stage 2. Back as stock & abused when i got it, after fixing oil cooler it still gets hot but over heating less. I cleened cooling system, he liked that. It spits oil out of the pvc pipe over the sensor, I isopropyl cleened it, hosed the oil out the charge pipe & "tried to" squert iso on the mass airflow, HE loved me for that.
i got a odb2 today say error codes dtc 2ef2 "intake/mas" turbo boost sensor dtc p0238 High voltage.
Mas reading doesn't move on odb2 so thats F'd, i think im at reduced boost running in limp mode until i do the Mas & maybe the boost sensor is reading wrong because of Mas 🤞
What i think caused this was 5yrs of abuse after swiss mini took off induction, adding a oem air filter, the cat back exhaust was gone, But i think the stage2 was left, so my cars been strangled. So much of your story are my symptoms. Im putting 500ml of oil ever 500 miles. With no visible leaks