u0121 and Reduced Engine Power

[amcnabb92]

Hey so a couple days ago I was driving and my reduce engine power message came up and put me in limp mode. There was a code for it but I don't remember what it was. And recently my boyfriend said that when he went into reverse it did not beep like it usually does and the ABS, traction control light came on with the code u0121. The only performance mods right now are a K&N cold air intake, and catless downpipes. My boyfriend is thinking maybe I just need a tune because the PCM could be getting confused...I'm not too entirely convinced that will fix the issue though. Anyone have any thoughts?

[Skillet]

As long as your boyfriend didn't go into limp mode you'll be fine.

But seriously U0121 is:
- Faulty Electronic Brake Control Module (EBCM)
- EBCM harness is open or shorted
- EBCM circuit poor electrical connection

Sounds like something else is wrong. You need to get all the DTCs being thrown - get them read at an autoparts store. Then at least you'll know what the problem is.

[Night trained]

My guess would be you have your DTC labeled incorrectly. A U code is a module malfunction. Recheck and you may have a P0121 which would do what you are describing. That DTC is a throttle position performance code. Check connections for corrosion< if ok more than likely a bad throttle body.

[christianchevell]

Having catless down pipes should make the o2 sensors have problems for one from the increased flow ( relayed reaction is one from headers due to moving a o2 sensor further down steam as position of them matters),and may cause a CEL, as could over lubricated air filter dirtying up the MAF sensor. People who put on headers usually get a Check Engine Light from it and require a tune, you may need one even without the headers due to the lack of cats, and tunes are not cheap usually. The three idiot lights come on from anything basically, and tuning it affect the stock tune in the ECM and is a warranty voider for many. Yes you need all codes being thrown as one can affect others.... A simple loose hose on a catch can could make a code. You could try un-plugging and re-plugging in the battery after a wait to see if new or different codes come up or if the all clear and go away.....also Backing up the reverse sensor only beeps if your near a object.....also Many get headers then a dyno tune or a canned tune from a vendor on a SCT or other brand of hand held tuner. You do not say how long since the exhaust change as it would make the exhaust less restricted and may require tuning yes, the deal is a tune for just changing to no cats is relatively unheard of because of the cost to just monkey with the cats as people on here usually have researched what change will affect the car, lots of young people come here and that's the first post: hey I wrecked, or I have big problem, etc etc so Research your own subject is the best thing I can say through the search at the top menu under catless or something and its hard to find things. You can of course also research a code via the computer with the codes from the obd2 scanner. Good Luck