'02 Maxima -- 147k miles

For about the last year, I have been getting the CEL only while driving on the highway. I don't drive on the highway that often, but lots of times when I do I get the CEL. The CEL never has come on during city driving.

The codes I am getting are....

P0139 - Heated Oxygen Sensor 2 Circuit Slow Response (Bank 1)
P0159 - Heated Oxygen Sensor 2 Circuit Slow Response (Bank 2)
P1147 - Heated Oxygen Sensor 2 Maximum Voltage Monitoring (Bank 1)
P1167 - Heated Oxygen Sensor 2 Maximum Voltage Monitoring (Bank 2)

My question is.....since these codes are for two physically separate oxygen sensors, is this maybe pointing to another problem?

Why would the two sensors be triggering at the same time?

Should I just go ahead and replace both of them?

What do you all make of the fact that this only occurs on the highway?

Thanks everyone.....

 

Anyone have any ideas here?

Thanks

 

I had a similar issue with my 2002 se auto.
My issue was just one of the sensors bank 2 I believe. It would come on ocassionally on the highway and then go off with some city driving.

Since the issue I have installed a grounding kit and haven't had the light come back in 3 months ( was like every week before).

Although a grounding kit my not be needed, consider the age of your battery and check your grounding points for rust

If you have access to an OBD2 scanner that can run tests it may show mixed results at least it did with mine. (2 out of 4 times) mine showed no codes

 

I'll go out on a limb and say that for normal "highway speeds" your exhaust has more heat going through it. Your guess is as good as mine as to how that affects your "Heated" sensors, but I usually don't freak out over O2 sensor codes if they come on randomly and my gas mileage is normal.
Plus I know when I drive my car hard, sometimes the CEL comes on briefly
Good luck

 

Maybe the main cat is clogged causing both precats to heat up.

 

Thanks for everyone's input so far.

I should add that the car is running fine. MPG is about 18-19 with 95% city driving. Seems normal to me.

Cat converter is not rattling and looks fine from the outside.