Found a solution to the P0193 CEL
 

Long story short, it's the fuel pressure regulator.


I tried researching what the problem was on the forum, but there was no definite answer. I had it towed to Subaru in Scottsdale after my BRZ broke down in the middle of the street and they replaced the battery stating that the HPFP "Wasn't receiving enough voltage". I decided to believe them and the next day my car broke down in the middle of the street again. Subaru said that it might be my mods so I decided not to go to them again.


I had it towed to a local tuner shop, where they removed the HPFP and tested the voltage (everything tested OK) and then they put it on the dyno to see where the fuel cut was occurring. They decided it was the fuel pressure regulator. They replaced the regulator and now the car runs great.


The other threads say it might be a bad HPFP, ECU, ECM, or IBU...but do yourselves a favor and spend the $100 to get the regulator replaced before you spend thousands on the above-mentioned parts. Just paying it forward!


-Steve

GOOD INFO!

Yeah, I figure everyone is pretty low miles still. But once they get closer to 60k this thread will be useful ;)

Since the dealer could not find the cause and turned you away, if your car is still under warrantee send a copy of the repair receipt to Subaru Corp Office and ask for your money back. They should honor your request

Got a p0193 this morning, car had been sitting since yesterdays track day. Car took a while to crank over but then fired up with a CEL and traction control light on.

Forums been down all day today so I’ve been eagerly waiting to click on this thread as it seemed OP had it figured out. Turns out I am the OP lmao!

Will try to diagnose tomorrow and will provide an update.

169k (nice) miles on the car.

ECU just needed a reset, so weird.

I wonder if it was never actually the regulator. Maybe it's an intermittent connection somewhere.

I was thinking the same thing. I wonder if this is a symptom of my BCM being fried after I expertly removed the door lights with a metal screw driver, with the harness still plugged in.

Definitely not. Except for the most whacky edge cases, fried components are a hard failure. This is one of a whole pile of closed-loop servo systems. There is a pressure sensor (feedback) interpreted by the controller (ECU) which then sends a corresponding output to the regulator solenoid.
A high pressure signal could be the result of the failed regulator, or it could be a sensor circuit open. If the result of a failed regulator, the pressure sensor MIGHT show a fluctuating reading. Open sensor will show hard high for sure.

So I didn't want to post anything due to embarrassment but the BRZ was broken down all of last week.

After I got the car back I let it sit which I should not have done as there was no time for the permanent code to clear. I started it up a few days later and bam P0193. However this time I was able to clear it with my open flash tablet. I start driving down the road and the engine shuts off and the CEL comes on. I am able to clear it in the middle of the road before the light goes green and pull into a gas station. The code would come back every time I turn off the car and turn it back again. I decided to randomly reload my stage 2 tune and the code went away and I could drive the car. Next morning same exact thing happens except this time the throttle doesn't work, and I can't clear the code with my OFT. I paid for one month of an app called "Auto doctor" on my phone which I was able to clear the code with. Drove around and the permanent code cleared. I was so excited except the next morning it does it again!! This time I am also getting a P0087 code which means the fuel pressure is low. So, fuel pressure is too high, while also being too low - right...

I decide to take off the driver side rail cover to inspect the HPFP and everything looked good. I didn't want to remove anything, so I simply unplugged the fuel pump, cleaned the connector and plugged it back in.

Shockingly, the car now runs perfectly. It has started fine the last week straight with no issues. Now I know unplugging the fuel pump probably didn't do anything. My main theory is that I got a bad tank of gas, because now that I have run 1/2 a tank of new gas everything has worked itself out.

Strangely enough while I was having issues, I was watching fuel pressure at idle. It would be pretty consistent @ 400psi, but then would spike to 3600+PSI but with 0 change in engine/idling behavior.

Perhaps my direct injection sensor is going bad but if it ain't broke right now don't fix it right?

While that hard high pressure indication doesn't quite fit the service manual cutoff for test, it fits the scenario perfectly. You have an intermittent electrical issue. If the pressure sensor connector hasn't been touched since it rolled off of the line, I'd feel confident going with the sensor going bad. The test procedure is quite detailed but use your gut. It's either the sensor, or wiring.

It is the original sensor indeed, 169k miles on it. I tried to remove the connector with the manifold on but that was way too hard. Will replace the sensor and report back.

Thank you for that link, what a wealth of knowledge!

Remember, not my stuff. I only link to it in my sig line. Good luck! Keep us posted.

An IT tune up!

Well I got another awesome 3 years out of her before this next P0193! This time it came back with a vengeance. Nothing I did with my OFT helped the disabled throttle. It happened as I was warming up the car for my next track session. Car now has 193,000 miles and I think I’m gonna finally start replacing parts. New HPFP, sensor, and radiator on order. I will post back when it’s all put together again.

https://i.imgur.com/rBbwTa4.jpeg

I’m having the same issue with the engine not starting, just stuttering for a few seconds at most when starting. I also track the car, also use an OpenFlash Tablet, and I’m also in NorCal, but the difference is my car is a 2017, I’m at only 44k miles, 63 track days. Zero issues up until I flashed my ECU back to stock tune after an engine rebuild and getting ready for a smog check.

Troubleshooting so far…

Reflashed software:
No difference.

Flushed out 0.5 gallons of old fuel:
No difference.

Checked low-pressure fuel system:
With a mechanical gauge to the low pressure fuel line, 64psi as found, specification 51-73 psi. Good.

Checked high-pressure fuel system:
Using OFT, reading was 204MPa or 29,500psi, and target was 4.03MPa. Specification is 3.00-5.00 MPa or 435 to 725psi. Bad

Checked codes:
P0193, Fuel Rail Pressure Sensor 'A' Circuit High"
P1193, incorrect intake air temperature voltage

Cleared codes:
Codes returns immediately.

Checked high-pressure fuel pressure sensor connector with a multimeter:
pin 1 - sensor 5V supply, measured 5.08V, good.
pin 2 - sensor ground, measured 0V and 0 ohms ground, good.
pin 3 - sensor output, measured 5.08V, bad. Should be 0.5V with 0 pressure and 4.5V max.

Pin 3 stays at 5V until a few seconds after the car turns off the ECU. At that point it measures 8.48 KOhm to ground.

It really seems like the ECU firmware is a bit corrupted and pulled two sensor inputs high. I’m going to continue with the Subaru P0193 troubleshooting guide. Maybe these ECUs can only be flashed so many times?

i have 1065 flashes on my ecu.
No one has ever seen a corrupted ecu in this car, Subaru and toyota swap them because they aren't allowed to reflash the ecm, only to update it if it's out of date
but surely you can try with another ECU if you have someone near you, but must be same generation and same transmission

Thanks, good to know.

I was monitoring HP fuel rail pressure with my OEM tune and the E85 tune. OEM tune is pinned at 204.00MPa while the E85 tune is at 4.00MPa and then slowly rises to 10MPa. The tune and OFT are seeming much more suspect.

Here is my diag from the local shop I had my car towed to. I since had it towed back north so I get to be the one to do it.

"Verified customer concern. Found code p1604 start ability malfunction and p0193 fuel pressure sensor circuit high input and p0087 fuel pressure too low began by using scan tool to monitor fuel pressure noticed high side pressure at 56 psi indicating a fault with high pressure side disconnected high pressure fuel pump spill valve and verified circuits are ok and found no issues applied power and ground to spill valve and noticed no change in pressure indicating faulty high pressure fuel pump also noticed erratic pressure readings from sensor one second reading 3000 psi and the other second about 1000 psi then 50 verified sensor connection was ok and circuits ok indicating faulty fuel pressure sensor recommend replacing high pressure fuel pump and pressure sensor"

I've also had minor suspicions about the OFT being the cause. It doesn't help that my p0193 journey began directly after I loaded my first tune 10 years ago. But even though flashing between tunes and using a scan tool to clear the permanent code have miraculously fixed the car, this time nothing is working. I can clear the code, but after 10 minutes of semi-rough idling the car begins to choke, and you can really hear this by how loud the direct injectors are. Then it withers all the way to a stall.

When you rebuilt your engine, did you replace the HPFP with the 2018 revision?

I have a 2017 engine so I already have a slightly different HPFP and reduced lift cam lobes if I remember correctly.

What updates happened for 2018?

To be honest I'm not too sure on the differences, I know the newest one was released as a "fix" for the crickets noise.

The newest first gen fuel pump is flat on the top, whereas the older ones are rounded on the top.

Here is the TSB:
https://static.nhtsa.gov/odi/tsbs/20...53209-9999.pdf

Yep, those are all the parts that came on my 2017 car. No cricket noises yet!

I need a few more test drives to confirm, but switching to your car’s year fuel pump and a replacement pressure sensor has the car running well again. I’m not sure which of these made the biggest difference but I’d bet it was the sensor.

https://i.imgur.com/azw3Gn7.jpeg

Sensor makes the most sense.

So far I haven’t had the issue come back on my car, but I have the replacement sensor ready to go.

And enjoy the new fuel pump. Mine is still like new after 63 trackdays, half on E85, so I guess it’ll hold up for the life of the vehicle.

I hope it lasts a while too. I wish I took the time to inspect the roller on the bottom of the HPFP's cam follower but taking that piece out requires some specialized rtv when putting it back so I wasn't going to mess with it.

I was able to go on a 20-minute test drive and the car is driving great again. Situations where I felt I had to slip the clutch more than usual to keep the engine happy is now causing me to chirp my tires. Time to relearn the car I guess haha.

Mine had zero wear on the roller; just a little bit of wear on the bucket above the roller from rocking, but nothing of concern.

If you do want to ever take the pump out you can use Nissan 999MP-1217H sealant and a high leverage ratio caulking gun. It’s cheaper than Subaru or Toyota for the same Three Bond 1217H.

Just as an update; the car is driving amazingly now. See everyone in 2028 for my next breakdown :burnrubber:

Can pre-facelift FRS use a 2017-2020 HPFP? is it hard to replace to get rid of the chirp sounds

Yes the updated fuel pump can be used on the 2013-2020 cars.

Honestly, even though I was dreading the install, it wasn't that bad. Once you remove the intake manifold everything is right there in front of you.

I personally replaced the gasket(s) on the banjo bolt and the hard line itself going from the fuel pump to the direct injectors.

__________________________________________________ ________________________________

Part of my online order from "Devil Subaru Parts":

FUEL PUMP - 16625JB022 - $527.10 (The shop that diagnosed my car wanted $1,200 for the pre-revision pump, lmao)

INTAKE MANIFOLD GASKETS(S) - 14035AA610 - $15.33 x 2 = $30.66

THROTTLE BODY GASKET - 16175AA420 - $10.01 (You can leave the throttle body on the manifold if you drain your coolant)

FUEL PIPE GASKET - 17540AA340 - $3.91

HARDLINE - 17540AA340 - $37.56

Subaru fuel line disconnect tool for the quick disconnect line that connects to the intake manifold: $14

https://www.amazon.com/dp/B018SV6G5U...fed_asin_title

Lmk if you have any questions, very happy to help.

Some helpful tips:

Pull the fuse for the fuel pump and try to start the car to get fuel out of the lines. As a second precaution let the car sit for a couple hours so the fuel can depressurize by going back into the gas tank. The high-pressure lines see thousands of PSI which can slice off a finger no problem so be careful. Put shop rags underneath the lines you are disconnecting to catch the fuel that drips out. Don't overtighten the 17mm lines. Prime the fuel pump before starting the car to check for leaks.