Got codes, need advice!

[twocanewayne]

Hey guys gotta question. OK I got a PO400 EGR flow malffunction last sunday then I noticed bad gas milage then I read the code again and now I pulled a PO170 Fuel trim malfunction also, that was yesterday. What should I do?? I have been reading up and Im going to test o2 sensor, what should the upper one be reading, what about the second one or the back one??? What tells me they are bad?? Why is it usually the top one? Also Im going to do a boost leak check. Can the o2 be causing the PO400 code? Or can the ERG being bad cause the PO170?Thanks for any help in advance

 

[twocanewayne]

Oh yhea i have a 95 tsi awd and is blowing to the atmosphere bad for the o2 sensor I have an auto tranny.

 

[spyderturbo007]

Please don't bump your own posts....you will get in trouble.

The FT Malfunction CEL is thrown when the ECU reaches it's adjustment threshold for fuel delivery manipulation. This is caused, normally, by a bad O2 sensor, as you found from searching. At idle, the O2 sensor should be bouncing around from about 0.20 - 0.85v. It should be a consistent fluctuation around 0.50V.

How did you read the CEL? If you have a scanner, you should be able to take a look at the actual voltage from that.

As for the rear O2 sensor, don't worry about it. If that was bad, you would get a Catalyst Efficency CEL. The rear O2 sensor is just in place to verify the functionality of the catalytic converter.

 

[twocanewayne]

Thanks for telling me about bumping . I got the reading from advanced auto. Thanks for the info on the 02 reading. I have a buddy thats bringing a scanner home to read the volts on the 02 to see if its dead.