I am trying to get a P0240 code (low cat efficiency) cleared. Of course it might be related to it being a well used cat(200k miles), but it might be the O2 sensors.

I have a cheap ELM327 reader and use Torque both of which seem to work. I get a reading for O2 sensor bank 1-sensor 2 but not for sensor 1. I have replaced both sensors. Is this normal or am I missing something? Is there a better free option than Torque. Any ideas on what the O2 sensors should be reading?

Thanks

 

The problem I am concerned about is why can't I see what is going on with sensor #1.

 

My fear is that it is the ECU that is buggard up and will need replacement. I can trend sensor 1 but it is always zero

 

Doubt its the ecu.

 

O2S1EQ is you upstream O2 sensor data. To better understand it, watch it as graph

 

experiencing same thing bank 1, sensor 1 no signal/graff
throwing system too lean P0171 / P0170
have any luck?

 

Did you try to watch it with torque app? Did you choose "O2 Volts Bank 1 Sensor 1"?
To see sensor 1 graph then you should choose "O2 Sensor1 Equivalence Ratio" and you can see what your sensor is doing.

 

Thanks for the reply!
Yes using Torque app.
If chose 02 sensor bank 1 sensor 1 upper screen blank.
If chose 02 sensor bank 1 sensor 2 lower screen shows live Graff.
Did you end up solving your problem?

 

To see Sensor1 graph using torque app. Go menu - Add display - graph - choose " O2 Sensor1 Equivalence Ratio".

Yes, I solved my problem.
My P0170 and P0171 was solved after cleaning MAF with cleaner and during maf removal I found a problem with one airbox clamp. It wasnt tight anymore and it had and airleak because of that. Tightened clamp and my fuel trim was nice again.

My thread: https://mbworld.org/forums/clk-class...p0036-cel.html

 

Thought I would post the long overdue resolution to this issue.
1) Torque was not reading correctly and when I tried another monitoring program it cleared the lack of that one reading.
2) After changing the O2 sensors the problem persisted thus I expected the old cat was failing
3) Bought a aftermarket CAT (needed one CARB rated, but was only listed for 2004 not 2005) but it fit fine. Got it for $400.
4) Breezed though the smog check, Has been working fine ever since. Yea!