New Evo owner quesiton Hey everyone my name is Sam and I'm a new Evo owner. Love the car just have some issues to work out.

I have a check engine light on, code P0135 (oxygen sensor heater problem bank 1, sensor 1)

I replaced the primary oxygen sensor (one right below the turbo) but the code comes back right after an obd2 delete. I tested the wiring, and the heater wires get 14volts at the oxygen sensor so wiring is fine. Why am I getting the p0135 then still? Perhaps previous owner maybe used tuning software and maybe changes some setting in the ECU? I'm just guessing, since I don't know what else it could be.

Other problem I'm having is the car has a test pipe and NO secondary oxygen sensor (cat and O2 are completely removed) but I dont get any emission related check engine codes, HOW IS THAT POSSIBLE?

Again only thing I know of that would completely delete the secondary O2 sensor (on some cars) is perhaps changing some setting in the ECU???

What do you guys think? Please any and I mean any suggestions, comments are appreciated. I'm willing to check anything but I don't know where to start.

 

yes you might have adapter for ecu that deletes the code.

if you have original car and o2 sensor, try putting them on and reset the battery,
see if it comes back on.

 

Isn't P0135 code for heater on the front pre cat o2? Is it possible to get the P0135 for the secondary emission relate o2? Shouldn't that be a different number code?

And no, I don't have the cat nor the secondary oxygen sensor. I might get a secondary o2 and install it in the exhaust with a spark plug fouler.

 

Sounds like previous owner trick the ecu. I read somewhere you can get away from 02 sensor in rear, but idk why it throwing a code for p0135.

 

its definitely the front o2 sensor heater circuit. for that code.
theres guidelines and such. short in wire or circuit. if cant fix short, replace front o2. which is expensive!
http://www.obd-codes.com/p0135

whops edit- didnt see u replaced it, did u disconnect the battery to reset everything? i dont know if there is a difference from that vs an obd2 scanner delete.

for the 2nd o2 not being there, there are threads about removing it completely. in this case its "electrical" not the mechanical fix. i believe u can do it in the ecu or some method with looping the circuit. search and you will find it. disable rear o2 i think is the title.

 

Yes I figured the secondary O2 was removed by ECU patch/delete and thats why I wasn't getting any codes for it, but still cant figure out the front o2 P0135 code.

New sensor, and wiring is fine, the voltage is there on the heater wires at the sensor so I don't know why I'm getting the code. I hate the check engine light. I'll try the battery disconnect but I don't see any difference between obd2 scanner code delete and battery disconnect (scanner delete might be better if anything IMO)

 

sorry for bringing this one from the death but i am having the same problem.changed the sensor with a new bosch sensor.cleared the CEL but it still coming back.
maybe the resistance is different than the oem sensor ?
just thinking out loud.

 

just started getting this issue along with high idle.. just a p0135 code..
I also just installed a downpipe ,hollowed out cat, and Innovate mx-1 wideband recently... So maybe i didn't plug the o2 sensor in or something.. Will check it out soon and get back.