P0108 - It's not what you thought it was.
 

Ok, I had a pesky P0108 check engine code on my 2005 r53 with 100K miles. It was driving super rich and you could feel the engine stuttering and choking in all the fuel it was getting, as well as smelling the gas. After some searching here and a few other forums I found it's related to either the MAP or TMAP sensor. For reference, the TMAP is the one towards the front of the car on the intake manifold. The MAP is on the side above the flywheel. Neither one is all that bad to get to. MAP = Manifold Absolute Pressure, TMAP = Temperature + Manifold Absolute Pressure. If you aren't sure, they look mostly the same outside, but the MAP has 3 pins on the sensor, while the TMAP has 4.

Using a bluetooth OBDII adapter and the torque app I saw that "intake psi" was maxed out up at 33PSI even with the engine off.

So I ordered a TMAP sensor. When it got here, not sure whether it was map or tmap, I swapped it out with the map sensor first. Car ran even worse. I swapped the factory map sensor back in and then swapped the TMAP. Ran the same as before I started swapping sensors. So I put the OEM TMAP back in... and it was magically fixed. It's worth noting that both of my sensors are OEM BMW parts, likely the originals.

So I drove it for a few days until it came back. I unplugged the connector on the TMAP, plugged it back in, but no dice, still no good. I pulled the connector again, and looked at the contacts and noticed the gap was super wide, and the contacts on the sensor are super thin. I used a small pick to bend the contacts on the harness connector closer, plugged it back in, and voila, it worked again.

I drove it few more days, and the code once more came back. This time I pulled the sensor, and saw that the contacts on the harness connector had opened back up. I plugged it back in, and sure enough, the map sensor reads 33PSI on the torque app. I cleaned the contacts on the sensor, and then added a little solder to each contact to make them thicker. This time when I plugged it back in I could feel a little resistance. I plugged it back in, installed it back in the manifold, and voila, reading 13.5 PSI with the engine off, 4.5-5ish with the engine on and idling.

When initially researching this I read about BMW dealers going through multiple sensors just to get a "good" one. I happen to work as an engineer designing load cells which operate on the same principles as pressure transducers, and it's odd that they would have so many issues. I think it's been the harness connector all this time.

If you get P0108 on your r53, clean the contacts, add just a tiny bit of solder to each of the 4 pins, and try again. Better than wasting money on parts. I know for all future repairs for this car, I'll be keeping an eye on this with other connectors throughout the harness.

Spread terminals, relaxed terminals, fretting corrosion...It all stinks!

Sorry to bump such an old thread, but this is probably often the root cause of the issue. I just solved this issue on my 2006 Cooper S JCW 210 by following this thread. A new sensor didn't solve the issue alone, but only after adjusting the connections in the connector with a small pick.

Try this first before buying a new sensor!

Thanks a lot :)

Came across thread as well in my search for answers to the P0108 as well... I'm curious if you are still running without issues? I'm at this point now (replaced sensors and adjusted pins) before throwing in the towel to take it in. I have adjusted my connector pins twice, the first appearing to fix the issue until I tried to drive it the next day, now this little hack isn't working. Guess I'm on to the soldering step to the sensor for a tighter seating from the pin.

Curious if anyone had just tried replacing the connector entirely, by splicing in a new one...

I never noticed your comment, but yes, it has been running without issues so far. I just had this code again, but that has to do with my mods, which raised the intake pressure significantly (reduced pulley, bigger TB).

Harness
 

We replaced both sensors , code came back again . Moved the harness around by the manifold on the tmap and the car dies. Inspected the harnes pins and looked worn out going to add a little solder for a tighter fit . Found a harness kit to splice a new one which would be better but soldering may do the trick
https://cimg0.ibsrv.net/gimg/www.nor...0704ec215.jpeg
https://cimg3.ibsrv.net/gimg/www.nor...cf1a9f65f3.png

Thats an even better fix!