Faulty Fuel Pressure Sensor

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!

 

Congrats on getting what appears to be a rare failure for these cars. Maybe the cx7 part isn't as robust

 

IMO, No need to pull the fuel fuse if you're working on a cold engine, running the car lean enough that it shuts off personally had never sat well with me, just catch whatever fuel with a rag and toss it outside to evaporate

 

I prefer holding the throttle all the way to the floor and cranking. Shuts off the injectors to allow you to clear a flooded engine.

 

Having similar problem, but my sensor ended up melting in two pieces haven't been able to find a usable replacement. Any ideas on where I might be able to find one P/N 0261545006

 

Quick search shows them available to ship from Amazon and advance auto

 

Were you able to read above 1500psi? Someone said this part # won't read above 1500 psi.

 

I'm wondering the same thing. I'm seeing a lot of contradictory info on the bosch sensor part number (aside from buying the rail complete with sensor and pressure relief valve). Some guys saying 0261545053 is what is needed, and others saying 0261545038 provides the correct pressure, yet others say the *38 doesn't seat right and leaks. If I try the 38, I'll let you know what it reads- have one in hand but didn't put it on yet.

 

By chance did you get around to swapping out the fuel pressure sensor? If not no sweat, just dealing with some fuel issues myself.

 

So I ended up having the 5038 in and it was reading ok..my hpfp desired and active pressures were very close together, but with my koeo my pressure was reading 80, then the next day 90, then finally 100psi. Mind you, everything in my fuel system is brand new(pump/filter/ infectors. Etc.) So I bought a new sensor from a part out (# 5006) and so far everything is looking perfect, koeo psi is 55-60 and active and desired are spot on.

What are your issues? If you believe it's your sensor, the Bosch sensor ending in 5006 worked for me (so far at least)

 

Can anyone confirm that these replacement sensors work long term and do not leak? I have a vehicle I'm working on and desired vs actual FPR are pretty much the same but the readings fall on its face every so often. We have a used replacement rail with factory sensor but if we can change just the sensor, that would obviously be much easier and cheaper for the customer. Why does Mazda expect the entire fuel rail replacement for just a sensor fault? That's like selling an oil filter without the gasket, must be purchased separately. Btw, vehicle application is a 2007 Speed 3 with some aftermarket parts and a tune. Runs rough and lots of soot at tailpipe suggesting rich running conditions. He bought the vehicle like this so we are just trying to work through it and see what he has. Thanks everyone!

 

OEM fuel pressure sensor is a Bosch part, unfortunately the old PN has been replaced by the one in the OP, there's a few threads around of folks using Bosch parts with success. Reading another thread user reports 0261545053

Definitely frustrating that you can't just buy the sensor, seems that gen 1 ( pre 2010) vs gen 2 (2010+) speeds may play differently with the sensors from the threads I've seen see this thread too https://mazdaspeeds.org/index.php?threads/fuel-pressure-issue-need-diag-help.12283/page-2#post-90439

 

Start a thread for this car. What have you done so far to try and fix?

 

I haven't replaced anything yet, I've just done a quick preliminary inspection, checked plugs, viewed codes and engine data. The owner doesn't have a lot of money to stick into his car so I'm just trying to gather up as much information as I can before diving into this repair. I'm not starting a whole thread on this issue being that there's already several threads on similar issues. My main questions were... Why is Mazdas repair protocol say to change the entire fuel rail instead of the FPS? Sensor replacement is easy, rail replacement is a pain. 2nd question is in reference to the Bosch sensor replacement and weather or not they leaked and if they held up and lasted.

 

So you come asking for help and we ask you make a thread, you don't want to make a thread but still want help?

Part of the point of making a thread for this is to archive information and make this easier to find for others in the future.

That being said I would imagine the point of failure on replacing just the sensor is going to be effectively sealing the threads.

Since the fuel rail sees high pressure you are going to need a suitable sealant. I would do some homework on that if I were you. I'm sure Permatex or Loctite offer something suitable but you'll have to figure that out

 

Also the sensor is one of about five different things that could be causing the problem

 

I apologize for the gravedigging on the post. This is a problem I had, and something I can provide insight to.

My source for the information I'm about to parrot is from Bosch themselves, I called up their technical division myself just today to gather this information.

The original part number for the speed3 fuel pressure sensor is part number 0261545006. This part was discontinued in 2012. You cannot get this new anymore. The *correct* supersession of this part is P/N 0261545053, as verified by Bosch.

0261545038 is NOT an interchange with either the original part number, nor the updated part number. For the remainder of this post, I will refer to the incorrect part number as *38, and the correct one as *53 (this should be intuitive, but I'm being verbose).

*38 is rated for 70 bar (1,015 psi). *53 is rated for 140 bar (2,030 psi). By installing the *38 sensor, there's a chance it may work just fine, but because it is not rated for the pressure that the Mazdaspeed3 and 6 use in the fuel rail, there is a likely chance that it will not read accurately. This is just luck of the draw, since no matter what, the sensor is operating outside of its specification by merit of it being installed on a Mazdaspeed. It also does not seal properly, and this is something I have confirmed, but I'm sure you could force it with enough self clearancing and torquing.

In cases where *38 does not read as your vehicle expects you will see:
- Low HPFP actual pressure under load (I personally saw 1600 max, after that, no readings).
- AFRs during load will hit 29, due to the lean conditions, and you will have misfires. In my case, I saw this around 3k rpm.

As a closing thought, part number 0261545074 is interchange with *53 and *06, this was found in the CX-7s and has also been discontinued. There may be a potential that one could use a Ford Focus ST sensor (part number BM5Z-9F972-A), but that's outside the scope of this post and not something I tested myself (STs run at near the same fuel rail pressure, and the sensor from Ford uses the same connector, pin out and thread pitch).

 

^^ This is how you do it folks.

 

Apologies, updating again. I went ahead and bought the Ford sensor to test out my previous theory. It ended up working and reading fuel pressure just the same as the Bosch sensor (I normally run the correct P/N as previously).

The Ford sensors (to include equivalents like Dorman 926-432) are much more readily available than the correct Bosch sensor. If you go this route your mileage may vary, but it did work on my car. If someone else wants to contribute to this experiment to conclude the Ford sensor working on Mazdaspeeds more than just my car, that would be phenomenal. Other than that though, now that’s all.

 

What's it peg at?