P0192 Code - Fuel Pressure Dropping to Zero

EDIT: Issue has been solved. Initially I cleaned the Spill Valve while I waited for a new sensor. When everything was back together, idle PSI was 0 and tapping the gas would make the car stall out. It was also clearly pig rich as the car smelled like raw fuel. From this I concluded that the sensor is bad (and dumping fuel into the rail trying to get it to raise pressure most likely).

Bosch 0261545038 is the correct sensor for the Mazdaspeed3. It looks different, however it is the correct one. It can be ordered from your local parts store as it is a Ford OEM sensor. To unbolt it all you need is a 27mm deep well socket. The one from O'Reilly's (where I got my sensor) worked. I recommend testing sockets once you have the sensor in hand to verify that they clear the connector as it's a wide one. OEM sensor is also 27mm.

Bosch 0261545074 IS NOT THE CORRECT PART. This part is allegedly for a CX7 however the connector is ever so slightly different. It'll still connect if you try however if you log pressure it will stay stuck at 2200+psi and the car will run like ass. Why Mazda used different parts and harnesses for the same damn engine I am clearly too stupid to understand, however that is unfortunately how it is. The OE sensor is not able to be ordered from Mazda without purchasing the entire fuel rail, so the above Ford one is good enough.

Hey everyone. A few weeks ago I got an insane "misfire" and P0192 code which is for: "Fuel Rail Pressure Sensor Circuit Low Input". Misfire essentially feels like the car just shuts off for a cycle, not like a spark misfire, which makes sense given the code.

The issue seems to spring up mostly when the engine is cold, however this is anecdotal as when the issue occurs I park the car and drive my track car which is somehow more reliable (that's neither here nor there). I have however had one misfire at WOT near redline. Issue will sometimes fix itself at which point the car drives perfectly fine in and out of boost, regardless of load. When the issue is occurring driving under very light load will sometimes help reduce the severity of the misfires, however they still occur.

Car: 2007 Gen 1 Speed3 115k miles. Engine and car are bone stock and has (to my knowledge based on the condition of the hardware surrounding the common mod points) always been stock. . 600 miles before the issue happened I had the AC compressor changed by Mazda themselves. I also replaced the spark plugs and gapped them to 0.028" The day before the issue started the tank was filled up with fuel from a local reputable spot. Two days later I filled up my Miata from the same spot which has no issues.

For logging the issue I used the Torque Pro app and an OBD2 Bluetooth scanner to connect to my phone and logged Fuel Rail Pressure. I wrote down the most common tests for testing the in-tank pump and HPFP and wrote down the data points. Here are the results:

Key On Engine off Test: 56-66 psi

Cold Idle: 980 psi

Idle 450-500 psi

Light Load (Cruise, no boost): 1250 psi

Medium Load (Light boost, accelerating from lights/passing): 1600 psi

High Load (WOT; High RPM): 1750 psi Steady; AFR's stay near 12:1

Engine Off (Relief Valve Test): 400 psi initial; Rises to 1740 psi over the course of 15 minutes before slowly dropping

During the Misfire: Fuel pressure will spike down to 0 PSI. For one instance fuel pressure dropped to 0 psi for an extended amount of time (10 seconds give or take) however the car stayed running fine with occasional misfire. The one event during WOT pressure seemed to remain around 1750 psi however I was more interested in AFR at the moment so it could have blipped, AFR's were 12:1 holding steady. When the car cools down again I will try and get a log of the issue to post.

It is currently my thought that the pressure sensor on the rail is the culprit. It seems unrealistic for pressure to drop to zero from ~1200 psi in an instant, then be back to normal. Similarly if the pressure actually is zero for an extended period of time, then the car should stall. The actual readings from the fuel pressure seem correct for properly functioning mechanical bits as well.

Counterpoint: Does the ECU even care about fuel pressure? It also doesn't make sense that if pressure was still in the line (IE an electrical issue with the sensor) that the car would misfire. Wouldn't the ECU be using the O2 sensor and MAF to calculate required fueling?

At this point I am probably going to pull the trigger on a new sensor and swap it out to see since it is the easiest option. I am asking however if my logic makes sense, or if there is something that I am missing.

 

I had this same issue pop up about 3 weeks ago. Starts and stalls, misfire and 0192. My maf is clean and I replaced my O2 sensor (which anecdotally fixed my car for 2 drive cycles). I've replaced my pressure sensor and have had absolutely no change at all. Finding the sensor outside of the entire fuel rail is a doozy. Have you tried anything in the last week since your post?

 

Are you still on the same tank of gas?

Stop boosting until you figure this out

 

Have you had the fuel pump seals recall performed yet?

 

Yes my issue was eventually solved today (at least so far) by swapping the sensor. Additionally I also cleaned the HPFP spill valve as well however after installing it the fuel pressure would not budge from zero no matter what and the car would not take any throttle. At that point I knew it had to be the sensor as the car was obviously getting enough fuel to idle!

After logging fuel pressure is lower than with the old sensor at higher loads, however AFR is good and car does drive like normal with zero hesitation and no drops in pressure. I'm in the process of updating all my threads about this issue so hopefully someone will get a good idea of how to fix theirs if they have the same issue.

 

Does this sensor read above 1500psi? I have the 5038 sensor and I was reading it won't go above 1500 psi