This Code

[MarkA Bryan 2]

Check Engine light came on today. PO136 rear oxygen senor behind the cat. only thing I could see is the mA were lower than the front two as there is no other rear one to compare to. Anyone have any ideas of what to look for? Truck has 134,000 miles on it, regular maint. always done.



Thanks for your help

Mark:banana:

 

[EddieS'04]

This what I get from my code. Not the rear. but the pasenger side.

O2 Sensor Circuit Malfunction (Bank 1 Sensor 2

)



P0136 - HO2S Sensor Circuit Malfunction (HO2S-12) The downstream HO2S sensor(s) are continuously checked for maximum and minimum voltages. The test fails when the voltages fail to meet the calibrated limits. Pinched, shorted, and corroded wiring and pins.

Crossed sensor wires.

Exhaust leaks.

Contaminated or damaged sensor

 

[Bill Koonce]

With 134,000 miles you can expect things like oxygen sensors to need replacement. But before you go off to buy a new one, check the connector to that sensor, and the wiring that leads to it. Needless to say, if you find damage, like a wire that's been rubbed down to its last strand, fix that first! A shot of contact cleaner and a little scrubbing with an old toothbrush will ensure that the connector is making good (or at least better) contact when you put it back.



If this cleaning and/or repair brings your sensor voltage back to normal, then you're done. If it improves the voltage, but not enough, I would order a new connector, and replace it; and if necessary, replace any wiring upstream of the connector that looks like it's in bad shape. If that brings back normal voltages, you're done.



If your connector/wiring is in good shape, or your repairs don't solve the problem, then before you order the new sensor, get some penetrating oil on the threads of the old one. Do it again and again. It's better to over do it with the penetrating oil than it is to have to weld in a new bung.