I've read a lot about other (mainly japanese) cars going into a "safe mode" or a "limp mode" when the service engine light comes on, but is this true about mustangs as well?

I've got a 2001 with an o/r h-pipe on it and i've installed mil-eliminators on it but the two rear oxygen sensors are still throwing a "weak signal"code. Would this be causing the computer to enter a safe mode to retard the timing or whatever to prevent knocking or detonation? I dont care that the light itself is on, i just dont want it to be hurting the performance or fuel economy of the car. Any ideas?

thanks guys (maybe gals)

-mark

 

bumpity bump

 

it should not go into a limp mode for that code, That code is not causing any potential damage to the engine so there is no need to put it into limp mode.

 

When the engine light is on, the ecu pulls timming and adds fuel for safety.

 

My exhaust came loose on the passenger side before the first O2 sensor, it caused a check engine light (never got the light checked) the car DID go into limp mode. It ran extremely rich and all the unburnt fuel was causing a horrible popping sound out of my huge exhaust leak [8D]

Yes, there is a limp mode, but that code, in most cases, does not cause the engine to go into limp mode but IT CAN HAPPEN.

 

If you have a code for your O2s it does absolutly nothing to the computer or effect performance in any way shape or form. All that light is for is to tell you you will fail an emmisions test.

 

To clarify what has been said--problems with the front O2 sensorsWILL cause poor engine performance, as they are the primary input for fuel trim management in closed loop mode. If they are bad enough the PCM may go to "limp mode", though that is rare--mostly the car will just run rich as heck because a failed sensor is telling the computer the mix is lean, it compensates by making it richer...[/align][/align]Failure (or perceived failure) of the rear sensors will cause the catalyst efficiency monitor to trigger a DTC, and illuminate the Service Engine Soon light--it will NOT affect performance.[/align]

 

Thats what I ment I guess I should have clarified that I was talking about the rear o2 sensors.

By the way the primary sensor for air/fuel mixture is the MAF the O2s are secondary.

 

The MAF is the primary sensor for the base A/F ratio, the O2 sensors are the primaries for the fuel trim--it's in the shop manual...[/align]

 

+1 Front o2'a will change your idle and fuel inrichment. 90% of check engine lights will not effect performance, but the front o2's will. Not the rears