# Advice on what to do about o2 sensor / while def system needing to be serviced



## VtTD (Nov 5, 2013)

If it's a soot issue, which I think is somewhat common for 02 sensors, can you just clean it off the sensor and see if it works ok?


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## mkohan (Dec 19, 2015)

CHVY89 said:


> Hey Guys
> I have a 2014 Chevy cruze Diesel with 63k bought it may of 2015 with 83 miles on it . My check engine light came on and i took to the auto parts store and said they couldn't get a reading. took it to Chevy dealer and they said is was my o2 sensor. i said ok i will fix it i have ordered the part and just received it but the computer in my car is telling me that my def system needs to be serviced. with my regin light on. and i have 50 more miles until it goes in to derate mode and the car will not go above 65 mph hour.
> so my question is will it hurt my car if it goes into derate mode? I plan on changing the o2 sensor myself and then taking it to dealer and letting them force regin it, considering they said that the computer will not allow the car to regin when check engine light is on and considering that the fact that its a 02 sensor is bad. i just dont want to get beat over the head wiht charges at the dealer ship if i can wait unitl Monday or Tuesday for them to force regin it if thats what needs to be done


Have you add DEF (Diesel Exhaust Fluid) recently? It might be low. The CEL and DEF light might not be related. Just a thought.


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## diesel (Jun 8, 2013)

Moved this to its own post. @CHVY89, You mention a few different things that are not clear. What do you mean by "regen light"? Is it the one I show a picture of in this thread:

http://www.cruzetalk.com/forum/201-gen1-diesel-technical-discussion/182210-its-finally-my-turn.html

Are you talking about the yellow light on the speedometer, right under 70 MPH marking? If so, that has nothing to do with a regen. That light indicates that the sensors have determined that your DEF is bad. I am dealing with this on my car too. It could be a number of things, including bad DEF, a bad DEF injector or bad NOx sensors. 

Have you had your car in for the NOx sensor recall?


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## CruzeDan (May 17, 2015)

The HO2S does not have anything to do with the DEF issue.


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## boraz (Aug 29, 2013)

goin into derate wont hurt the vehicle.

have fun driving it that way though.


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## Sowerss1 (Nov 21, 2016)

We have a 14 Cruze TD. 57k miles
Bought it new.has been in the shop for two weeks now with poor quality exhaust fluid light. They have changed several sensors and the converter. Had the o2 sensor changed over a year ago, fixed the problem for awhile. Then replaced the unit inside the def tank. Every year when it gets cold out the message comes on and off periodically. My wife really likes the car, 
But definitely has some quality issues. Dealer seems to be working had to fix it but haven't figured it out yet. We have a 14 duramax and so far no def issues. 
Not sure what the difference is.


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## diesel (Jun 8, 2013)

Sowerss1 said:


> We have a 14 Cruze TD. 57k miles
> Bought it new.has been in the shop for two weeks now with poor quality exhaust fluid light. They have changed several sensors and the converter. Had the o2 sensor changed over a year ago, fixed the problem for awhile. Then replaced the unit inside the def tank. Every year when it gets cold out the message comes on and off periodically. My wife really likes the car,
> But definitely has some quality issues. Dealer seems to be working had to fix it but haven't figured it out yet. We have a 14 duramax and so far no def issues.
> Not sure what the difference is.


Did the dealer do proper diagnosis? Throwing sensors/parts at it is NOT the way to go. Most likely cause is the DEF reductant tank reservoir heater .


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## CHVY89 (Nov 18, 2016)

Yes I have had the recall changed and it was just changed 2 weeks ago. I will add def fluid and see if that helps. But the dealer ship said that the o2 sensor was bad. But i will try these things and see what i come up with. 

Thanks


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## mkohan (Dec 19, 2015)

See this....you should get the DEF issued fixed by GM

#29400: Special Coverage Adjustment - Diesel...


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## revjpeterson (Oct 2, 2013)

The speed limitation mode won't hurt the car--just annoy you, and incrementally limit you further until you're stuck at like 5mph. It's there to prevent driving with faulty emissions without addressing them. The car could run fine forever with most emissions issues un-repaired. 

Your O2 code and DEF warning are unrelated, since those systems don't influence one another, but sometimes dealers who don't know what they're doing read a NOX code and mistake it for an O2 sensor, and a NOX code could be related to your DEF issue. Some parts catalogs even list the NOX sensors as O2 sensors instead. Do you happen to know the actual code or codes that are set right now? That would help us guide you better with this. 

If it is, in fact, an O2 code, like P0133, it's possible it only needs to be cleaned. I have had the P0133 code twice. The first time, the sensor did require replacement, and the dealer did so under warranty. The second time, I was out of warranty, so I pulled the sensor and cleaned it before ordering a new one. I've gone 4000 miles since without a return appearance of the code.


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