D40 P102b - undefined code, found boost control sensor. Does the car need it?

[vskclint]

Hi everyone,

Just a couple of questions. Recently coming back from the bush, I had the car go into limp mode with a fuel rail pressure sensor code. Changed out the sensor as it was giving me a zero pressure reading on OBD scanner. Did the pedal dance to reset everything and away I went. All around town etc was good until I tried to go above 2000rpm roughly 100kph, then felt the car hold back (sort of limp mode). It didn't matter how much I pressed on the accelerator it would go any faster. OBD scanner came up with P102b - Undefined. So after doing a lot of research (and I must say this forum has helped me with a few other snippets of very helpful info, Many thanks to you all), pulling what's left of my hair out and a couple of night's playing around I came across a post with this same issue. Check the boost control sensor up near the turbo and there's the issue.

From the manual it's called an exhaust pressure sensor but i've found it as a boost pressure sensor. Which one is it? What is it roughly in charge of? and does the car actually need it?

ATM its disconnected with no codes or issues, hence my questions.

The car is a 2012 vsk auto with no DPF. I've checked all the earth points and added a couple of more and the last thing I haven't done yet is to pull the SCV and clean it, hesitant for the moment as I'm not having issues with it or is it something I should be looking at?

 

[Brad20v]

Hi
The SCV controls the fuel pressure on this diesel. They are fairly common to play up, with lack of power etc. The best get out of trouble fix is to remove it and clean ,but rotate 180 degrees when re fitting as they wear.
Won't cost anything but your time to try.

 

[Old.Tony]

^ As above. You could even try a bottle of injector cleaner but if your hands are ok and you can undo the electrical plug and the two torx bolts holding it in, go for it.

The boost control is either by vacuum (vacuum pump on vehicle right hand side of engine, hose goes over the top and on to the Boost Control Solenoid then onto the actuator on the turbo) - or it's electrical and there's a connector on a widget mounted on the turbo (there was a recall early on relating to these, but haven't heard of many problems since).

Boost (manifold) pressure is detected by a sensor normally on the cold side of the intercooler (actually in the hard pipe on the vehicle right hand side, allowing you to remove the intercooler without having to unplug it). This has rarely been a problem reported here.

The usual culprit for the described symptoms is the SCV, thanks @Brad20v for being so quick!

 

[Ziad]

Hi
The SCV controls the fuel pressure on this diesel. They are fairly common to play up, with lack of power etc. The best get out of trouble fix is to remove it and clean ,but rotate 180 degrees when re fitting as they wear.
Won't cost anything but your time to try.

Hi Brad20v, great inputs, just to know, would it make noticeable difference once reinstalling SCV back180 degrees?

Thanks

Ziad

 

[vskclint]

Thanks for your responses guys. Had a chance to get to the scv this morning before the heat . pulled it out gave it some love and put it back in 180deg, also plugged the boost control sensor back in and took it for a drive. Threw the same code on the drive so disconnected the bcs, cleared the code and drove off with no other issues. I've attached a pic of the bcs in question and also the scv before cleaning it.

Had the car sitting in the drive idling, disconnected the maf at the air box and got a code, plugged back in. Took the intercooler sensor off and threw a code, then went back to the bcs disconnected and no code. So i can only assume the bcs is playing up or is there something i should be looking at on that circuit?

 

[Brad20v]

Just wondering, what fuel pressures does your obd2 say you have.

 

[erol ashık]

 

[vskclint]

@ idle 30-31000kpa
@60km roughly 65000kpa at 2lb of boost.
@100km roughly 105000kpa at 8lb boost.

 

[Brad20v]

I could be wrong and need to confirm, but I'm sure mine is quite a bit more, 105000kpa about 15300psi, I think mine is around 30,000 might be the higher boost though.

 

[Old.Tony]

The 4cyl D40's fuel pump produced a max pressure of 1700BAR (just shy of 25,000psi) and the 6cyl V6 diesel's fuel pump produced a max pressure oof 1800BAR (about 26500 psi). If you're producing more than that you might need to have a diesel mechanic take a squiz at it, or there's an issue with the pressure sensor on your car (which will cause problems with fuel delivery).

 

[Brad20v]

Checked mine today, i was incorrect, 22psi a little over 20,000psi

 

[Old.Tony]

Checked mine today, i was incorrect, 22psi a little over 20,000psi

That's no drama at all, well within the system's normal range.