Hello everyone,

My Montero Limited 2002 got the check engine light on, according to my OBD scanner the reason is a faulty oxygen sensor located upstream in the second bank (P0155). Have anyone faced this issue before? What are the side effects of having this error code (low mileage, emission compliance)?

I noticed my miles per gallon (MPG) has decreased but not sure if it is related the oxygen sensor malfunction.

Regards

 

Same issue. Except I replaces the o2 sensor and still have the same problem. 01 XLS. Help.

 

What do you mean by same issue? Still the CEL on?
I'm replacing mine with Denso 234-4742 bought on Amazon. Many people recommend me to stay away from Bosch O2 sensors.

 

Unfortunately I replaced the O2 sensor second bank and it made no difference.

 

Which brand did you bought? I'll let you know my results once it is replaced.

 

P0155 means the O2 sensor responsible for calculating proper fuel/air mixture is not working. It can be an issue with the sensor itself, or in the wiring harness leading to the sensor. Since several posts indicate that replacing the sensor didn't fix the issue, I would suggest that you examine the wiring harness leading from the sensor to the PCM. You might have an issue in the connector or a broken (burned) wire somewhere along the way. There is a process for checking the harness. Look it up and follow it from sensor all the way to PCM unit.

 

HunterD

Thanks for the guidance. I did it the opposite way by measuring the resistance on the O2 sensor and it seems to be open circuit so probably it died. I'll replace it and if the CEL is still on definitely your procedure is the next step to follow .

 

Its possible that O2 sensor is dead. I found diagnostics steps for 2003 Montero. Yours should be very similar. I hope it helps.

 

Thank you, I already downloaded and stored it for future reference just in case.

 

i would love those steps if you still have them, i know dead thread... but i had a p0154 and replaced that o2 sensor, now i have a p0155