Engine Fail Safe on Nana
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Joined: May 28, 2020
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From: SC
Engine Fail Safe on Nana
I'm new here. I have a 2005 v6. I have a love for ponys. Even more off a love to work on them. Recently I have been thrown in fail safe engine mode. Now my alternator went I'm out. My concern is my first visit into the oil change shop and the same day started one of many problems..HELP!!
Code I got is: SU8794 (FUEL RAIL PRESSURE SENSOR)
Code I got is: SU8794 (FUEL RAIL PRESSURE SENSOR)
Last edited by nanaspony1227; May 28, 2020 at 08:58 PM. Reason: Adding code
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Joined: February 2, 2004
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From: Insane
It's not likely the oil change did anything, it's coincidence at best.
That code isn't.... right. Not only is it not a code from the OBD2, it's a part number for a Duralast (Autozone) fuel pressure sensor... that doesn't fit your Mustang. It's for Grand Marquis and other Mercury (and Mazda) cars, it seems.
So. I have to throw that out because it makes no sense, sorry.
In the realm of the fail safe engine mode... that's with the wrench light on, not check engine, goes to idle and won't rev, right? That's *probably* the throttle body motor, or possibly the throttle position sensor. The code reader would probably give you that information, or it may be just a generic 'can't figure out what's up with the throttle, I quit' (although probably something less wordy than that.)
The alternator being bad before then, however, could have been the problem all the while. Voltage issues can cause lots of weird problems, like this. I'm going to link my battery thread regarding the entire battery/charging system and what you might want to do to try to fix that first. Lots of things that can cause the problems to surface. And usually, if the battery's bad, the alternator's going to go next, and vice versa. These cars are well known for not being great about the charging system in general, every bit of help to keep it happy is best. Also check your grounds, there's a few in the engine bay. Make sure they're good, not rusty, and attached well. I also recommend, silly as this sounds, that you just get the cheapest battery for the car, unless you're going with a red top optima or something, because they're all made by three manufacturers, so it doesn't matter where you get it or who's on the label... aka, go to Walmart, cheap, same, and good 2 year warranty swap program. There's no point paying more. And if you get all that stuff in the thread done, it'll outlast that warranty by quite a bit. Might get 5 years out of it, like I did the last battery. Quite the achievement, actually.
Silly charging systems in these things...
If you get more info, let us know. Hope that helps. Welcome to the forums!
/Battery thread... well, the post anyway: https://themustangsource.com/forums/...4/#post6917899
That code isn't.... right. Not only is it not a code from the OBD2, it's a part number for a Duralast (Autozone) fuel pressure sensor... that doesn't fit your Mustang. It's for Grand Marquis and other Mercury (and Mazda) cars, it seems.
So. I have to throw that out because it makes no sense, sorry.
In the realm of the fail safe engine mode... that's with the wrench light on, not check engine, goes to idle and won't rev, right? That's *probably* the throttle body motor, or possibly the throttle position sensor. The code reader would probably give you that information, or it may be just a generic 'can't figure out what's up with the throttle, I quit' (although probably something less wordy than that.)
The alternator being bad before then, however, could have been the problem all the while. Voltage issues can cause lots of weird problems, like this. I'm going to link my battery thread regarding the entire battery/charging system and what you might want to do to try to fix that first. Lots of things that can cause the problems to surface. And usually, if the battery's bad, the alternator's going to go next, and vice versa. These cars are well known for not being great about the charging system in general, every bit of help to keep it happy is best. Also check your grounds, there's a few in the engine bay. Make sure they're good, not rusty, and attached well. I also recommend, silly as this sounds, that you just get the cheapest battery for the car, unless you're going with a red top optima or something, because they're all made by three manufacturers, so it doesn't matter where you get it or who's on the label... aka, go to Walmart, cheap, same, and good 2 year warranty swap program. There's no point paying more. And if you get all that stuff in the thread done, it'll outlast that warranty by quite a bit. Might get 5 years out of it, like I did the last battery. Quite the achievement, actually.
Silly charging systems in these things...If you get more info, let us know. Hope that helps. Welcome to the forums!
/Battery thread... well, the post anyway: https://themustangsource.com/forums/...4/#post6917899
Thread Starter
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Joined: May 28, 2020
Posts: 6
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From: SC
Update
Thanks for explaining that. As of this am I'm back up and running with new Alternator. I haven't had a problem again with fail safe mode. Seems to be doing ok as for now. Although "check engine" light is still on.
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