Does anyone know if these codes mean both Oxygen sensors are bad in front or in back? Is there a cheap generic replacement? Why would they both go bad at the same time?

 

I Have the same codes and can not seem to find an answer some say its a bad MAF and some say its the O2 sensors. I called the dealer near me and told them thhe problem and told them it was running fine and they said to just leave it or pay the 90 to 150 bucks for them to tell me what hopefully find out for free on these forums.

 

Good observation! Not likely to happen. Codes indicate a lean condition on both banks. Vacuum leaks. DII how many miles?

 

1999 D2 with 99,500 miles. I am thinking Vacuum also. Now I have to figure out how to find a vac leak.

 

I don't how much this will help,
my shops Alldata's shows PO174 as
Multiplicatlon injector adaptive fuelling lean limit exceeded RH bank.
PO 171 is the same thing for LH bank.
Some of the things the Alldata shows for the problems are.
1.Fuel pressure regulator fault-pressure incorrect.
2.MAF sensor inaccurate.
3.Fuel pump fault-flow too low.
4.Part load breather pipe.
With both sides showing the samething I would think the O2 sensors are ok.
Good luck Mike

 

First check the air cleaner box. There are alignment tabs. If one of them is bent over it will cause an air flow disturbance over the MAFS and result in problems. It can also allow unfiltered air to contaminate the MAFS.