O2 Sensors no activity

[Modoyadney]

Hi,

Since I got my truck I get error codes for my O2 Sensors (the ones behind the cats).
I have replaced both sensors. After that they at least didn't show any voltage related error codes anymore.

After I delete all the errors they usually show up after some driving, sometimes after shorter trips not at all.

The most common ones are P0140/P0160 (O2 Sensor no activity detected...)
Sometimes error codes for the heater and about the cat efficiency show up as well.
The cat for bank 1 deffinetly has some loose parts in it and might be broken...
The other ones seems fine. The last emmisions test was passed as well.

I'm just wondering why error codes show up from both banks and they are a little different all the time.

Has anyone tried one of these little O2 simulators? I might just get two of them and try out what happens.

Truck drives normal. There is no lack of power or excessive fuel consumption, as far I can tell.

 

[exp500]

Take a look at the manual for troubleshooting those codes and system operation. Your Cat converters may well be used up, but a little reading and a bit of diagnostics may help you decide next step.
Look here too- https://www.tahoeyukonforum.com/threads/helpful-links.131971/

 

[OR VietVet]

Sure "sounds" like the cats are needed and I would do the front sensors at same time. I love spending other people's money.

 

[Eman85]

That code can be a pain. What's interesting is my pickup doesn't have any cats but it has the sensors and doesn't set a code. I've had others that set the code but after multiple clearings and some hard driving never returned. Be sure to check the wiring itself as any poor connections can cause problems.

 

[Modoyadney]

Well, I bought these chinese O2 simulators just for fun and installed them.
The error "O2 sensor no activity detected" still comes up every once in a while for both banks.

So far I have checked all the easy to reach connectors. Nothing suspicious there...

At least the simulators seem to do their thing, errors about the cat efficiency didn't appear since then.

When I got some time, I'll follow the procedure from the manual.
I just find it interesting that the error always appears for bank 1 and 2.

 

[Modoyadney]

I did the whole procedure described in the manual today and ended up with ECM replacement...
What i find very odd, is that the voltage of both rear O2 sensors are stuck at one voltage. Both got exactly the same voltage, 400 and something mV.

Even with the O2 sensors disconnected the scan tool reads this voltage from the car.
Has anyone ever heard about something like this?

 

[exp500]

Ohm test both rear O2 sensors. Test Grounds :VS battery. The ECM's were alway considered near bulletproof, but like most of us here "jus gettin old".

 

[swathdiver]

Something killed your cat. It's breaking up and whatever killed it, is killing your O2 sensor. Silicone, fuel, oil, coolant.

If none of that is occurring, the wiring is good, it's the ECM, time for a new computer.

Sign up for the shop manual so you can run through the troubleshooting guide if you are serious about fixing this correctly. AllDataDIY.

 

[Modoyadney]

Yeah, one cat is damaged, might have been just the age. The engine is in a good condition, no oil or coolant consumption or any funny noises or smells.
And since the last emissions test was passed the other cat should do its job.
I will buy an universal cat and weld it in but I am not sure if this will fix this problem.

The scan tool always shows a fixed voltage value of 445 mV for both after cat sensors, while the front sensors jump in a specific range.
No mather what I do it is always the same, engine off, engine idling, full throttle and even both rear sensors disconnected the voltage is 445 mV.

I might try the manual you recommended and see what they say. With the Chevy manual I ended up with replacing the ECM.
Next thing I'll do is look for someone with a more professional scan tool and see if they get more information out of it.

I'll keep you updated, maybe other people run into the same problem like me.

 

[swathdiver]

Yeah, one cat is damaged, might have been just the age. The engine is in a good condition, no oil or coolant consumption or any funny noises or smells.
And since the last emissions test was passed the other cat should do its job.
I will buy an universal cat and weld it in but I am not sure if this will fix this problem.

The scan tool always shows a fixed voltage value of 445 mV for both after cat sensors, while the front sensors jump in a specific range.
No mather what I do it is always the same, engine off, engine idling, full throttle and even both rear sensors disconnected the voltage is 445 mV.

I might try the manual you recommended and see what they say. With the Chevy manual I ended up with replacing the ECM.
Next thing I'll do is look for someone with a more professional scan tool and see if they get more information out of it.

I'll keep you updated, maybe other people run into the same problem like me.

Careful with universal cats, cheap cats don't last. Shop manual says that fixed at 445 mV indicates a short to Voltage.