I got my R53 back from the mechanic for a head gasket + valve job, but in less than a mile it lit the MIL (check engine), it doesn't keep idle very well and at constant throttle it stutters, especially between 2 and 3000 rpm (I guess because it's closed loop). Clearly running super rich: bad mpg and soot coming out of the exhaust. Intake pressure on Torque is always 34psi constant, even with engine off.

No problems at WOT or at constant throttle but above 3200 rpm (I guess because it goes to open loop).

Diagnosis is:
P0108 - Manifold Absolute Pressure/Barometric Pressure Circuit High Input [current fault, doesn't let me clean it]
P0036 - HO2S Heater Contro Circuit (Bank 1 Sensor 2) [stored fault, lets me clean it but it recurs]. Probably just caused by the first issue.

Now, I have taken out the MAP and TMAP sensors and they look ok, TMAP was wet in oil but delicate cleaning with solvent didn't solve the issues.

Is there a way to check the wiring with a tester to see if power and ground are good, before starting to blindly change the sensors?
My suspect is that rebuilding head and radiator, the mechanic has shorted the sensor wires.

 

Also check to make sure there is not a leak in the supercharger inlet pipe or the BPV.

 

What is the contractual obligation of your mechanic for doing the head job? Don't he/she has the obligation of not messing up the electronic engine management system? Was the car running fine up to the departed valve?

Cleaning sensors and hoping they will be cured is one of the biggest automotive service myth. The pressure sensor is a piezoelectric transducer and it either work or kaputt. Cleaning it will not make an Iota difference to its functionality if it has departed. Also unless from road salt corrosion, Mini's wiring harness is very good. The problems are often because of the mechanic.

 

Yes he has the obligation, but I'm not sure it's the wiring and for a number of reasons I prefer to give it a go myself before giving the car back.

Is there a way to check the wiring from the connector with a tester, to avoid disassembling the front to physically check it?

 

Have you actually checked the sensors with a meter to verify one is not bad or a scan tool to check what the data says?

 

the scan tool gives the errors reported in the first message

As for the first question, I'd love to, but how do I check the sensors with the meter, do you know the correct values and the pins to check?

 

You have to know what value at normal atmosphere pressure they ought to read. I doubt this info is given. Check the useless Bentley manual. I would not count on it.

 

Read and make sure you understand this fully before proceed. I am too busy for other things so I won't spend time on it. The pressure transducer output is a voltage, but I doubt you can just disconnect the harness and measure it. Do it at your own risk if you not up to electronics and what a piezoelectric sensor is.

https://workshop-manuals.com/mini/co...ams/page_5536/

 

A tip to help you think. There are two MAP sensors. One is for DME to know the atmospheric pressure, and the other the boost pressure. If you understand the cursory of boosted engine work, you should be able to deduce which one may be faulty.

 

If the scan tool errors out trying to read live data I would try another one.

Once you see the actual data it will show you exactly what is going on.

pnwR53S has posted the voltages you are looking for.

 

Just to be clear. I am quite sure you are not going to be able, nor should you, to measure these voltages with a meter. The voltages are to be reported by the DME to a diagnostic tool.

 

yes, I'm quite sure too I can't check the voltage out of the sensor in working conditions, but couldn't I check for open circuit or short in the sensor with a meter in the resistance setting (ohmmeter) if I knew the two pins for power and ground, sensor-side?

also, couldn't I do the same harness-side, putting the meter in voltage mode and checking first the power, then the ground pins of the harness with key-on to see if the (currently disconnected) sensor is correctly powered or there's a short/break in the wiring harness?

@dowinshift1: I use a elm327 obd2 bt adapter and torque pro, I thought the intake pressure constant at 34 psi even at engine off was the problem (high pressure read -> a lot of fuel in -> running rich). You are suggesting the scan tool is not reading properly?
Might I be better off using ISTA-D/Rheingold?