This is a new one because I could not find it in a search. P0159 - Heated exhaust gas oxygen sensor circuit slow response (bank 2, Sensor 2). Based on the description, I assume this is an oxygen sensor. I did put two of them back in the car that was older because I thought it was an O2 sensor issue with my other codes. However, I replaced both upstream O2 sensors, and the code is telling me that it is a downstream sensor?

 

Sensor 2 would indicate that it’s the downstream sensor.

The downstream sensors are the ones that do the heavy lifting. The upstream really only act as a check to make sure that the downstream are working.

 

Thanks, Vee, Kind of funny I am not having problems with the older ones but it is the new ones that have been issues

 

Pins 3 and 4

These pins on the O2 sensor side of the pigtail connector will be the heating element

Don't cross whole connector positions when hooking back up , so 1 connector at a time

There is a different wire color on pin 3 between the fwd and aft O2 sensor pairs

On the car side of the connector the wire colors will be for the aft sensors pin 3 Blue / Pink ( UK ) and pin 4 White / Green , and fwd sensors pin 3 Blue / Brown ( UN )

You have 3 other connectors to compare your resistance values against

 

Downstream sensor, serving Cylinders 4,5,6, which serves the rearward exhaust, or the cylinders furthest from the radiator/front of car.

That's the one you need to replace. (I would do both, as the other one is probably not long for this world either)

 

Man I should have kept big red. Got the p0159 along with P0139(O2 Sensor Circuit Slow Response (Bank 1, sensor 2) and P1138 (Lack of HO2s12-sensor indicates rich). If I had hair I would not have any more

 

Clean the grounds?

Have you visited the ECU connectors ?

This will be the Red color connector

B1S1 - 6

B1S2 - 16

B2S1 - 19

B2S2 - 18

Look for 1 of 2 pincging tabs missing and give the wire a slight tug on the back of the connector

 

Hey, these sensors are not made to last forever. Swap 'em out and hopefully that'll be all she wrote.

 

I replaced all 4 when I first got the car so I don’t think that is my issue

 

Might have to give the ECU some time until they learn the new sensors

There can be a sensor bad out of stock

 

I don’t think there’s a learning curve to the sensors.

When did you last swap out the sensors? What brand did you use. (I’m assuming they were new). Did you swap out all 4?

You may want to check your ECU harness connection. If you are getting moisture (not uncommon) this can happen. I would definitely check for signs of corrosion or water at the ECU.