Randomly getting CEL w/ code P0193
 

Hey all,

About once every two weeks or so my car has some trouble starting. It'll take the normal time for the engine to turn over, but a CEL will come on, and the car will not drive properly at all. It won't rev and goes at most 5MPH or so. I'll shut the car off and start it back up, the CEL will go away, but it'll rev constantly from 750RPM up to 1500RPM. I turn it off and on again, and sometimes it'll go back to the CEL or it'll repeat the constant revving.

I used my OpenFlash Tablet to read the engine codes and got a P0193. A Google search turned up a lot of stuff on Fords but nothing relating to Subarus or even Toyotas, but the Ford information says it's relating to the fuel pump. I'm able to clear the code and usually the problem will clear up after doing so. Sometimes it takes several startups before the issue goes away and I'm able to drive the car normally. When the issue goes away the car seems to drive just fine, no lack of power, weird noises, or anything that indicates there's a problem.

I can't seem to find a common denominator between all these instances. It doesn't seem to matter if it's super cold, because I've both had it happen and not happen on days where it's below 0. It's also happened (and not happened) on warmer days in the fall. It happened both before I put in the Perrin intake and after so I don't think the intake is the issue. I also had it happen before I put the Vishnu tunes on the car.

Any insight onto what the code means? I'm worried that if I bring it to the dealer I'll just wait an hour and be charged labor because they looked at it and couldn't replicate the issue or find a problem.

Probably ecu man

This is all I've found.
http://engine-codes.com/p0193_toyota.html

Same thing with subaru
http://www.car-ii-codes.com/p0193-subaru.html

Definitely take it to the dealer, fuel pump issues when going WOT can be very detrimental...

Alrighty then, I guess I'll make an appointment for next week.

And thanks for those engine code sites. Bookmarking them now!

From the OE Scion / Toyota diagnostic info for P0193 is
DTC

P0191

Fuel Rail Pressure Sensor Circuit Range / Performance

P0191
One of the following conditions is met (2 trip detection logic):
Fuel pressure is 19.2 MPa or more when 9.5 hours or more elapsed after ignition switch turned off.
Fuel pressure is 1.9 MPa or less for 10 seconds or more with engine running when 5 hours or more elapsed after ignition switch turned off.

Possible causes
Open or short in fuel pressure sensor circuit
Fuel pressure sensor
ECM

Usually even if it doesn't happen they can run the scan tool and see the history / Pending codes and it should show up.

So, an update. I took the car in for service at a Subaru dealer Tuesday last week (the 21st). After waiting for about an hour, they told me they couldn't find anything mechanically wrong and flashed an update to the ECM, citing an "out of range error". They weren't specific about what that meant.

Anyway, the car ran fine (even through two of the coldest nights we've had here in a while) until tonight when I started it up to go to work. CEL came on, and after I let the car idle for a few seconds it started doing the constant revving from 750 to ~1500 again. Shut it off and started again, same thing.

I checked the codes with my OFT again, and this time I got both P0193 and P0191. I cleared the codes and started the car, still got the CEL with the revving. Shut it off and tried again, and I still had the CEL but at least the revving stopped. I let the car idle and warm up for a few minutes while I brushed the snow off and the car drove normally, so I could at least get to work.

I haven't put the tune back on the car since I left the dealership, so this is with an entirely stock ECU. Looks like I'm making another appointment. There has to be something else wrong.

I brought my car in to the dealer again, but left both codes in the DTS so they could see them. After about an hour of waiting the service advisor comes out and tells me they're considering replacing the ECU completely. Alright, I say. I wait a little longer, then they tell me they need to go drive the car "in a certain way" to get some special data from the car. I give the go-ahead, and the advisor tells me it'll be a while before it's ready. So I head to the nearby mall to grab something to eat.

I come back and get an update from the service advisor. He tells me that the problem I'm having is because of the cold air intake. His theory is that the car is getting more oxygen than it's expecting and the fuel pump isn't able to supply enough fuel initially to start the car, causing the code. What doesn't make sense to me is that if that, assuming the pump is working fine, the codes I should be getting from the ECU would indicate that the engine is running lean, not that the fuel pump isn't getting enough voltage or the rail pressure sensor is out of range. And because they've deemed the intake the cause of the problem, they won't provide any more warranty assistance with this issue.

He said the next thing to do is for me to remove the intake and put the stock airbox back in, then they can look into the issue some more. I tell him I'm not willing to go through the uninstallation when I'm not convinced it's the problem, but he won't budge. Since there's nothing more he's willing or able to do, they put the car back together and I sign the paperwork, get my key, and go. Fortunately they didn't charge me for this visit because nothing was resolved.

For some reason they're completely unwilling to consider the fact that the issue could be with the fuel pump and keep suspecting the ECU and now the intake, and I don't see how it's possible that could be the case. The dealership has taken every chance they can to NOT find out what the actual problem is, and unfortunately there isn't another dealer in the area I can go to.

I'm thinking I need to write a letter to Subaru of America (and forward it to my attorney as well) saying that I disagree with their diagnosis and ask them to look into it. They have yet to provide a scientific explanation that fits the error codes I'm getting.

Any thoughts?

Put the factory intake back on and see if the problem recurs. The intake isn't helping the car anyway.

whats the intake you have on your car?

nevermind just saw it lol

if it was an aem intake then yeah those little "tunes" that come with the car tend to fail after awhile

It's irrelevant whether the intake helps the car or not. I don't want to take the intake off because I don't believe it's the direct cause of the problem, ergo it's not worth the time to take it off. In any case, once I got the car back home I flashed to the most recent Vishnu OFT tune since the dealer seems content to do nothing. The tune may help.

However, I do have another theory. Since I got the car I've been filling the tank at the employee-only gas station at my work because we get a 10-cent discount per gallon. The station does have 93 octane, but contains ethanol. I'm starting to wonder if the station just has lousy gas. I've filled up twice at a station in town that has ethanol-free 91 just because it's been more convenient recently to fill up there, and I've noticed my gas mileage has gone up by almost 3MPG with no changes in driving style. So, for the next few weeks I'm going to fill up there exclusively and see if that helps at all. Unfortunately I haven't found a conveniently-located station with ethanol-free 93.

Can you ask them to log fuel pressure?

It is not your intake most likely. I'm getting the same issue and 0191 code and all I have is a drop in filter

Dealerships are anal about ANYTHING aftermarket.

Just take the intake off and let warranty take care of it for you. Then put the intake back on.

Mine has been also doing the same thing for some time now. NO MODS at all. Its has been at the dealer 2 times and a total of 3 and half weeks. The answer I get is that they can't figure it out and working with tech line. P0191 and gas pedal stops working.