Toyota MR2 MK3 2004 - Are These Readings Within Normal Limits?

After replacing a straight pipe with a catalytic converter and fitting a new exhaust, my car threw a lean code and the check engine light came on (after driving it for a short distance).


I cleared the code and it hasn't come on since (I've done quite a few trips in it now).

I'm planning to take it on a long trip this week so I just wanted to get some feedback to see if these readings look ok.

At Idle





Accelerating


Constant Speed


​​​​​​

Well from data it is reading rich right and if you recently changed the cat did you change o2 sensors as well? Did you also reset fuel trims?

I didn't reset the fuel trims. Would I do this by resetting the ECU?

The post cat sensor was replaced as there wasn't one fitted when the straight pipe was on.

You will need a scanner that is capable to do it or take it to a shop/ dealer to have them reset it otherwise it will be done automatically but will take time for the computer to relearn the fuel strategy as it learns while car is driven and in closed loop. I would not recommend resetting ECU unless you know for 100 percent certainty that it will not effect other areas of ecu's programming. I.E vin identifiers and anti theft and software updates that have been done.

Thank you for your reply.

I reset the ECU as I found out that it does not cause any issues. However since then the issues with the car have worsened so I've written a comprehensive description of the problems below. 

Overnight I removed the ECU fuse and upon re fitting it and taking it out for a drive, the bank 2 O2 sensor was stuck on high voltage at idle, bank 2 was lean and bank 1 was rich. These were the readings I was getting back:





I've since taken the car on a 3 hour drive and the problem has become a lot worse. I had to take the roof down as fumes from the engine in the cabin were pretty strong. 

The exhaust is now a heck of a lot louder (and not in a good way), performance also seemed a bit choppy towards the end of the trip (slight lack of throttle response and otherwise just not seeming 100%). The o2 sensor readings had also gone completely haywire on both sensors:



Post drive I've gone to have another look and the CEL has come on and is throwing out the following codes:

============1==============
P0136
Raw code: 0136
ECU: 10
Status: Confirmed
OBDII: Heated oxygen sensor (HO2S) 2, bank 1 - circuit malfunction
Toyota: Oxygen Sensor Bank 1 Sensor 2 Malfunction

============2==============
P0153
Raw code: 0153
ECU: 10
Status: Pending
OBDII: Heated oxygen sensor (HO2S) 1, bank 2 - slow response
Toyota: Oxygen Sensor Bank 2 Sensor 1 Circuit Slow Response

=========================
P0150
Raw code: 0150
ECU: 10
Status: Pending
OBDII: Heated oxygen sensor (HO2S) 1, bank 2 - circuit malfunction
Toyota: Oxygen Sensor Bank 2 Sensor 1 Circuit Malfunction

============4==============
P0136
Raw code: 0136
ECU: 10
Status: Pending
OBDII: Heated oxygen sensor (HO2S) 2, bank 1 - circuit malfunction
Toyota: Oxygen Sensor Bank 1 Sensor 2 Malfunction


============1==============
P0136
Raw code: 0136
ECU: 10
Status: Confirmed
OBDII: Heated oxygen sensor (HO2S) 2, bank 1 - circuit malfunction
Toyota: Oxygen Sensor Bank 1 Sensor 2 Malfunction

============2==============
P0153
Raw code: 0153
ECU: 10
Status: Pending
OBDII: Heated oxygen sensor (HO2S) 1, bank 2 - slow response
Toyota: Oxygen Sensor Bank 2 Sensor 1 Circuit Slow Response

=========================
P0150
Raw code: 0150
ECU: 10
Status: Pending
OBDII: Heated oxygen sensor (HO2S) 1, bank 2 - circuit malfunction
Toyota: Oxygen Sensor Bank 2 Sensor 1 Circuit Malfunction

============4==============
P0136
Raw code: 0136
ECU: 10
Status: Pending
OBDII: Heated oxygen sensor (HO2S) 2, bank 1 - circuit malfunction
Toyota: Oxygen Sensor Bank 1 Sensor 2 Malfunction

============5==============
P0136
Raw code: 0136
ECU: 10
Status: Confirmed
OBDII: Heated oxygen sensor (HO2S) 2, bank 1 - circuit malfunction
Toyota: Oxygen Sensor Bank 1 Sensor 2 Malfunction


I've looked around the exhaust and can't find any obvious signs of a leak. This was the only location (exhaust paste pending removal)  where there was slight movement in the tissue on stick, even then it was hard to tell if it was just the air causing the movement. I also looked around the manifold seal and couldn't see any signs of movement there. 

imgur.com/a/64N2Ywg

This is a reading from last year taken from the B1 O2 sensor last year when the decat pipe was on and by the looks of things it didn't look 100% then?

https://i.imgur.com/Ky9LkGM_d.webp?maxwidth=640&shape=thumb&fidelity=medium

Any suggestions on where to start? 

Ok for bank 1 sensor 2 you will need to check the fuse. If fuse is good check for voltage at fuse and at bank 1 sensor 2 connector if test ok then there will be a few more tests to do. Which you will need a 4 amp bulb (turn signal bulb like a 3057/3157) to load test the wires going back to pcm and from fuse box to o2 sensors

as for the rest of the sensors you will need to create a vac leak while watching o2 sensor readings to see if the go lean. if they do then the next thing to do is create a rich condition by spraying carb cleaner or propane into intake vacuum port and see if they all react rich. if they don't react one way or the other or both then those sensors will need replaced.