Chmiggle
Greenie N00B Member
This might help those who anyone who's experiencing fueling issues and reading 0psi of HPFP fuel pressure, or those who swapped in a JDM motor to replace their stock one like I did.
TLDR: Bosch 0261545038 is the sensor you need, use a 27mm deep well socket to remove/install.
The stock motor on my 2012 Speed3 threw a rod and I decided to replace it with a used one from a JDM CX7 back in July 2022. The swap went well, but I started experiencing fuel pressure issues shortly after. The car would run great until HPFP pressure suddenly dropped to 0 and the engine would bog like crazy. It wasn't a gradual drop either, it literally went straight from 1200psi to 0 and back again. At first it seemed to be happening most often at 5k rpm, but soon enough it was happening at 2-3k or even idle and for longer and longer periods of time, pretty much making the car undriveable. If the engine bogged down for long enough it would throw codes P0300 and P0192.
I looked around the forums/online and followed the common advice of cleaning the HPFP internals, checking the ground by the HPFP, replacing the pressure relief valve on the fuel rail, and replacing the in tank fuel pump. While replacing the ITFP, I noticed the flapper at the end of the low pressure relief line had pretty much disintegrated and I thought that was the root of my issues (see this thread). I replaced it, put the car back together, and drove around town no problem. After trying to go on a longer test drive the next day, however, the fuel cuts were back.
I never stopped to question if the fuel pressure sensor itself was the problem, though, and it turns out it was. Below is a picture of the faulty one from my JDM motor, P/N Bosch 0261545006.
The replacement sensor is Bosch 0261545038, and it looks different from the part pictured above but works just fine (corroborated by this reddit post). My old engine also had the same sensor. Maybe this other one is less reliable? Idk. Here's where it's located.
The shop manual says that the sensor needs to be replaced along with the fuel rail if it's faulty, but honestly I don't see why that would be necessary unless the rail itself is cracked/leaking. To replace: pull the circuit fuse and run the car until it dies. Also preferably work on a cold engine so it doesn't spray hot fuel at you as you're trying to take out the sensor. Put some paper towels around it to catch any fuel that might leak out.
Removing it is very easy, its accessible from the top of the engine without taking off anything but the intercooler cover. Unplug it and use a 27mm deep well socket to remove - the socket might sit a little crooked b/c the intake manifold gets in the way but the sensor doesn't need to be torqued down much at all so it's fine (don't have an exact torque spec, sorry).
I talked to my mechanic and he gave a pretty good explanation as to why the faulty sensor caused the car to bog. When it sees 0 psi, it assumes there's no fuel in the rail so it starts dumping in as much as possible, making the engine run really rich and bog down/misfire. This also makes sense because the car reeked of fuel when it was reading no pressure. I thought that since the HPFP is mechanical, the ECU would rely on the O2/MAF sensors to decide how much fuel to give, but clearly it takes fuel pressure into account too.
I've driven over 100 miles with no issues since replacing the sensor, whereas before the fuel cuts would start happening within 10 minutes of me starting the car, so I'm pretty confident this did the trick. Hope this helps someone else!
TLDR: Bosch 0261545038 is the sensor you need, use a 27mm deep well socket to remove/install.
The stock motor on my 2012 Speed3 threw a rod and I decided to replace it with a used one from a JDM CX7 back in July 2022. The swap went well, but I started experiencing fuel pressure issues shortly after. The car would run great until HPFP pressure suddenly dropped to 0 and the engine would bog like crazy. It wasn't a gradual drop either, it literally went straight from 1200psi to 0 and back again. At first it seemed to be happening most often at 5k rpm, but soon enough it was happening at 2-3k or even idle and for longer and longer periods of time, pretty much making the car undriveable. If the engine bogged down for long enough it would throw codes P0300 and P0192.
I looked around the forums/online and followed the common advice of cleaning the HPFP internals, checking the ground by the HPFP, replacing the pressure relief valve on the fuel rail, and replacing the in tank fuel pump. While replacing the ITFP, I noticed the flapper at the end of the low pressure relief line had pretty much disintegrated and I thought that was the root of my issues (see this thread). I replaced it, put the car back together, and drove around town no problem. After trying to go on a longer test drive the next day, however, the fuel cuts were back.
I never stopped to question if the fuel pressure sensor itself was the problem, though, and it turns out it was. Below is a picture of the faulty one from my JDM motor, P/N Bosch 0261545006.
The replacement sensor is Bosch 0261545038, and it looks different from the part pictured above but works just fine (corroborated by this reddit post). My old engine also had the same sensor. Maybe this other one is less reliable? Idk. Here's where it's located.
The shop manual says that the sensor needs to be replaced along with the fuel rail if it's faulty, but honestly I don't see why that would be necessary unless the rail itself is cracked/leaking. To replace: pull the circuit fuse and run the car until it dies. Also preferably work on a cold engine so it doesn't spray hot fuel at you as you're trying to take out the sensor. Put some paper towels around it to catch any fuel that might leak out.
Removing it is very easy, its accessible from the top of the engine without taking off anything but the intercooler cover. Unplug it and use a 27mm deep well socket to remove - the socket might sit a little crooked b/c the intake manifold gets in the way but the sensor doesn't need to be torqued down much at all so it's fine (don't have an exact torque spec, sorry).
I talked to my mechanic and he gave a pretty good explanation as to why the faulty sensor caused the car to bog. When it sees 0 psi, it assumes there's no fuel in the rail so it starts dumping in as much as possible, making the engine run really rich and bog down/misfire. This also makes sense because the car reeked of fuel when it was reading no pressure. I thought that since the HPFP is mechanical, the ECU would rely on the O2/MAF sensors to decide how much fuel to give, but clearly it takes fuel pressure into account too.
I've driven over 100 miles with no issues since replacing the sensor, whereas before the fuel cuts would start happening within 10 minutes of me starting the car, so I'm pretty confident this did the trick. Hope this helps someone else!
