Can the rear O2 sensors alter air/fuel ratio?

[J DAWG]

I am curious what signal they can send to the PCM. Can they tell it to add orr take away fuel?

My car has hi-flo cats.




John

 

[Tom F&L GoR]

They are there to monitor the performance of the catalyst. Their signal is compared to the signal of the front sensors; if they are in tandem, the ECU is happy, if not, the emissions systems sends a code. They don't affect fuel strategy.

 

[onerareviper]

Tom,

Couldn't the Viper go into 'Safe mode' if the rear O2's sense a problem, tripping a 'Check Engine Light' and then richen the fuel? If so, I guess it is an all or none. No 'Check Engine Light' no effect on Air/Fuel. Yes to 'Check Engine Light', effects on Air/Fuel.

I think.

 

[Jack B]

They only set a soft code which does not affect a/f.

 

[Tom F&L GoR]

As Jack said, rears would only set the dash light on. It's the EPA's way of making the car company tell you that the emissions system (catalyst) isn't working like it's supposed to. But the engine management part can still be working fine, since it's the before-cat O2 that sees what the engine is doing. Because the check-engine light is associated with so many, very different things, it's not intuitive to know how serious it is.

Dodge has a system to let you know what the code is (short of buying a $100 OBD-II reader) where you cycle the key: key on-key off-key on-key off-key on and count the blinking yellow light. The numbers are all two-digit codes. The blinking dash lights are the universal codes, so they are the same as any other US car. You can find the diagnostic trouble codes by searching for diagnostic trouble codes... or post here.