Hi all,
Got a sob story and need some help. So I'm moving from Austin to Chattanooga and 100 miles out from Austin my car, which was full of stuff and running the AC in 100 degree weather, all of a sudden loses power. I manage to nurse it to a gas station a couple of miles away by keeping the revs below 2500 or so.
Basically my car has gone into limp mode. I pull the codes and get a 17 - Feedback System (poss O2 sensor) - Feedback cancelled. I have no idea what this really means. Some have said 02 sensor, which I replaced to no avail. So I paid the $230 to have it towed back to Austin. Two days later, my Dad goes to move it out of the driveway and says that it now runs fine (it didn't when he pulled it off the tow truck, he says). So now I'm going to be flying back to Austin to try to fix a car that's not currently broken and I don't even know where to start. That it was broken and now isn't is annoying.
I've had this problem once before and all I did to fix it was to disconnect the battery and hold the brake pedal for a minute. Worked great for another year.
Any ideas? I'm completely out and would love to be able to fix this before I try to make it to Chattanooga without the benifit of my fiance following me in the truck.

Thanks,

-Mark

 

does it throw a check light when it goes into limp mode. if so, stop driving and check the code before turning off the car. my guess is OMP/MOP

 

Code 17....quickest way to fix that is to run a wire from the 02 sensor straight to the ecu.

You want to clip the wire that runs into pin 2C. Then spice in the wire you ran from the o2 sensor. When you look at the picture...the point of view is ALWAYS from behind the connector (wire side)

\

The wire is all black


Might be a broken wire in the harness.

This code has nothing to do with the oil injection system.

James

 

Gotta love that ever evading OMP code, lol. A lot of times the thing will ONLY show up after driving about 5 minutes, and then if you turn the car off, it'll clear.

 

^word!

 

an o2 sensor will have nothing to do with the described symptoms of "limp mode". you can drive the car without one and will only suffer slightly worse freeway milage.

when my car had the evasive omp problem, i could drive it out to redline in 1st with a shift to 2nd and then some before it would go out on me (not that that was a good idea, limp mode triggers fuel cut) but i didn't know what was happening at the time.

 

Code 17 does cause limp mode....

 

Oy, this is confusing. I've never seen anything in any manual that ties the omp/mop to code 17. If the omp was bad, wouldn't it be throwing the codes for the omp/mop (20, 27, 37 or some such)? Plus I've once forgotten to connect up the O2 sensor and driven it for a couple of weeks with it only throwing a check engine light after 10+ minutes of driving.

Why do people think that the omp has anything to do with code 17? My manual says it's the emissions feedback system (O2 sensor). Since my problem has gone away after a couple of days, I can't help but wonder if the people who replaced the omp had a similar experience. i.e. they had to wait for the part and in the interim the car became interested in driving again.

This has the feel of some kind of heat related short but again I don't kno that much about the feedback system. The shop manual is somewhat vague about it.

Any more ideas or anwers to this and these new questions?

-Mark

 

Dude, I gave you teh answer to your question.

You run a wire from the o2 sensor straight to the ECU by passing the stock wiring.

Really, what more can be said about this?

Your right this has NOTHING to do with the omp.

James

 

Thank you sir may I have another!?

I was just harping on it becuase there's so much confliciting info out there and I'd love to know why on earth a code 17 would cause the car to go into limp mode. Can't it just ignore the o2 sensor and use a richer fuel map? Seems kinda silly to me.

Anyway, I did run a wire from the o2 sensor straight to the ecu and drove it around on the highway on cruise control for about 1/2 hour. Had no troubles with it at all and when I got back I checked the codes and only had the 33 in there. I feel some better.

Does anybody know what conditions must be met for the ecu to kick into cruise mode?

Thanks for all the replies!

-Mark

 

A faulty o2 sensor or one not hooked up does NOT cause limp mode. Limp mode is when the car will not allow anymore than 25% throttle, or higher than usually ~3000rpm (can nurse it up to about 3500 sometimes).

As for the nothing to do with the OMP. Since the O2 sensor sure the hell doesn't cause it, you generally look at things that DO cause limp mode, which would be the obvious omp!

 

If the OMP is causing the car to go into limp mode, and limp mode is a determination made by the computer, then shouldn't I be seeing some kind of error code related to the omp? I sure would think that there'd be some kind of code involved. I mean, the computer is getting info that something bad is happening and not coughing up a code seems stupid.

 

I think what sonicrat is trying to get across is that the only actual error that will cause limp mode on an S5 is a problem with the OMP. I'm almost positive myself any issue with the o2 sensor will not cause limp mode. It may cause your car to run rougher, etc or feel like "limp mode" but by definition it wouldnt be limp mode. I've known people with s5's and s4's who have run their car without the o2 sensor connected and no dramatic driveability issues at all.

An example is on S4's is if your waterthermosensor is malfunctioning your car may go into what seems like a limp mode.

 

When the OMP "goes out" usually it shorts internally and fries the ECU from sudden over current in that circuit. When my OMP went out i think it just threw every code possible, must have showed like 12 codes. So could it be possible that if the OMP fries the ECU that it might give or not give codes with no rhyme or reason?

 

Like I said, the OMP can be tricky to find. Sometimes it only will throw the code when it happens, and you can't turn the car off/etc otherwise it vanishes until it happens again.

 

I've also had limp mode like symptoms that turned out to be a stuck throttle sensor - narrow range (code 18). The plunger was stuck all the way in and would not come out unless you really pulled on it.

Whether or not it was "true" limp mode doesn't really matter, but if it drives like limp mode, it bucks like limp mode and has no power like limp mode, it might as well be limp mode.