Check Emissions message & light - hesitation - O2 Sensor? Which one?

Car felt very lump and hesitating under part throttle , then seemed to be fine, then again it hesitated worse - full throttle and higher revs it seemed to be fine again but then all of a sudden CHECK EMISSIONS light illumunated. #


OBD reader has 2 codes:


P0135 - 02 Sensor Heater Circuit (Bank 1 Sensor 1)

P0420 - Catalyst System Efficiency Below Threshold (Bank 1)


I presume the O2 sensor needs replacing, but there's 2 as I understand it, 1 pre-cat and one after? - is there any way to know which one has failed and needs replacing?


If I drive the car in the meantime can it cause engine issues?


Thanks for any help in advance!


(Car has KTEC manifold and decat, if it's relevant)
 

Foxspeed

"the new red baron"
Moderator
ban k 1 = first sensor the second sensor is used for odb2 monitoring and making sure sensor 1 is working right

if you know someone with an obd2 plug with live data check the lambda sensor voltages they should be up / down if they are slow to change then thats an issue
 
Thanks for the info. I'm using Torque (Pro) with an ELM327 OBD bluetooth device , I can't seem to see lambda sensor voltage as an option so I don't think the app or OBD device support it.

I'll order the first Lambda sensor and see if the code reappears after clearing.

Cheers
 
Were you able to solve this ?

I have the same symptoms, maybe even worse:

ERROR: P0141: O2 sensor heater circuit BANK 1 SENSOR 2 ?

I assume i have to change the second sensor ?

Thank you.
 

Addison

Paid Member
Were you able to solve this ?

I have the same symptoms, maybe even worse:

ERROR: P0141: O2 sensor heater circuit BANK 1 SENSOR 2 ?

I assume i have to change the second sensor ?

Thank you.
I had this on mine yesterday funnily enough. It is possible the second sensor will need changing, I cleared it in hope it was just a false reading so it may be worth doing that first. I've yet to have it come back up.