P1135 error code----CHECK ENGINE LIGHT still on after replacement 02sensor

Already replaced CO2 sensor??

Checked wiring under car--know this, never been under my car-- so bear with me
No wires stiking out of sheathing----cant unplug what I believe is CO1 sensor??
In front of cat, right?

You all seem so knowledgeable, just want to learn

Thank you!!

 

You can`t find the plug??

You can`t figure out how to get the plug apart??

It helps to know just what your working on .

A Code is the complete sensor circuit the sensor the wire and the ECM

The PO135 is the heater circuit .

Was the O2 sensor replaced with a cheap replacement??

 

2002 Toyota Tacoma 4 cyc--220k miles

Check engine light never went off after replaced 02 sensor, then unplugged battery and new code came up with

Sensor Heater circuit malfunction Bank 1 Sensor 1

So is 2 sensor I changed, ok--?

Now bank1 sensor1 code-----on 02 sensor or 01 sensor ????
Now know 1 is upward 2 is downward, correct. Is that 2 cats then??

It wasn't a cheap part- I looked under car for plug/wire maybe not connected/frayed etc. Plug firmly in place so cant disconnect.That plug my friend said is connected to 01 cat (o2 was replaced).

Sorry if not using correct terminology. I can take pictures under car tomorrow if needed.

Thank you for replying

 

Bank 1 Sensor 1 is the upstream O2 sensor (before Cats). Unplug the sensor and check across the sensor connector for continuity. If its open (no continuity) then the sensor is bad. With the mileage on the vehicle its possible both O2 sensors went bad within a short period of time of one another. If after changing you get P0420 then you may have a bad cat.

Also, I recommend not disconnecting the battery to clear the CEL code. If you don't have one get a code reader that allows you to clear the codes themselves. When the ECU is hard reset it goes into test mode until all driving modes are encountered which can be a couple weeks depending on your driving habits. Clearing just the code should only need to test the failure and does not reset any 'learning' the ECU has done on your driving habits though even in this mode the tests need different driving modes to finalize.

 

Robert,
Basically saying after downstream sensor changed and “ engine light” still won’t shut off, need to change cat 1...? Just 200k miles could do this?
I can’t budge sensor at all—-for sensir1....looks connected..
Is the code reader like one use st AutoZone or higher quality one?
Where would you by it?
Thanks !!!