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!