2006 Camry OBDII Catalyst Monitor Test Will Not Complete!

2006 Camry, 4 Cylinder, Automatic, 185,000 miles.
My OBDII showed a P0420 error code and the problem was isolated to the post catalytic Oxygen sensor, which was replaced.
The error code was cleared after the oxygen sensor was replaced.
I have since driven the car for eight weeks and the OBDII catalyst monitor test will not complete. I have driven in excess of 2000 miles, driving the Toyota recommended driving profile many times, to no avail.
I have no OBDII error codes and all other monitor tests are complete, but the catalyst monitor test will not complete. I even disconnected the battery. After reconnecting the battery all OBDII tests, except for the Catalyst Monitor test complete in less than one day of driving!
I have driven the Toyota recommend profile to get the tests to complete with no positive results, just a lot of unhappy people on the highway!
Can someone please tell me how to get the ODBII monitors to complete?
I am in despite need for it to complete as my emissions test is due in several weeks and I will fail if I have any incomplete tests.

The first thing you should know is that it is unlikely that a P0420 will be solved by a bad rear oxygen sensor. It is possible if the sensor was intermittently having an open circuit and dropping to zero.

A new rear sensor will be even more critical of the catalyst than an old sensor.

Not many catalytic converters are working great at 185k miles.

Be certain there are no exhaust leaks in front of the rear converter because this can set a false P0420.

Use scan tool to check for pending codes. Rectify pending faults.
Use scan tool to check that all other monitors are ready other than catalyst.
If oxygen sensor monitor is not ready, suspect you still have a problem there.

=== begin drive cycle ===

Fuel tank 1/2 to 3/4 A/C off.

Start car cold engine and idle for 5 minutes. Rev engine in park at steady 2500 rpm for 2 minutes then return to idle.

Use scan tool to check voltage reading of bank one sensor two. The voltage should be steady around .600 If voltage is bouncing between .100 to .700 then the catalysts are bad or there is an exhaust leak.

Drive on freeway for 10 minutes then pull over and idle in drive for two minutes. Drive the car under 45 mph for another 10 minutes. The catalyst monitor should either be ready or fault.

Are you sure you’ll fail the Emissions test if there’s only 1 monitor incomplete? I am am an Emissions tester here in Pennsy & here, if the car is '00 model year or older you can have up to 2 incomplete monitors. If it’s '01 or newer, you can have 1 monitor incomplete.


This is how I understand the situation . . .

If a car fails the smog inspection because of a cat code . . . when the customer brings the car back for the recheck, the cat monitor MUST show “complete”

Maybe I’m reading too much into this

db4690–regarding tonyreo’s '06 Camry, all I can tell you is, in PA, as long as you don’t have any codes, yes, you could have the catalyst monitor incomplete (if that was the only incomplete monitor) & the car would pass, even if the car originally failed because of a cat code (although I’ve been told by emissions instructors that there’s still, like a .01 % chance it COULD fail; don’t ask me why.) Moreover, although tonyreo’s code was a “catalyst efficiency” code, it was determined that an O2 sensor was the culprit, not a bad cat. Maybe tonyreo can tell us what state he lives in.


Scenario . . .

Customer in PA fails smog test because of cat code
Car gets repaired somewhere
Car shows up for retest . . . with all complete except cat monitor
Car passes smog
MIL is on 2 weeks afterwards . . . with the same cat code

Doesn’t make much sense to me

As for determining that the oxygen sensor was the culprit . . . none of us except OP were there. And we’re just assuming the diagnosis was correct, and that nothing was overlooked.

Such as . . .

updated sensors to address P0420
updated cat to address P0420
updated pcm software to address P0420

db4690: In your scenario, what would make the MIL come back on?

You’re right about what the culprit could be. I’m only temporarily assuming the problem was properly diagnosed.


In my scenario . . . and perhap’s OP’s scenario, as well . . . the MIL came back on because the car was not properly diagnosed in the first place

I’ve seen it a few times, and presumably so have you

By the way, I’m not talking solely about catalytic converters, but about repairs and diagnosis in general

What State do you live in? In NY State you cannot have a check engine light on but you can have one I/M not ready to test.

Hi Guys,

Thanks for the help…
I live in Ohio and according to the state website "…If diagnostic data has been erased during vehicle repairs or through battery disconnection the computer reports systems as “incomplete” or “not ready.” Vehicles are rejected from testing when these diagnostic checks are not completed.”
So it appears Ohio will not pass you unless all monitors report as ready.
Also, I have no “Check Engine” light on now. The oxygen sensor was diagnosed via a scan tool. It was monitored and was found not to be toggling the expected voltage. So it was replaced and the error codes cleared.

Call the e-check number for answers about how many monitors have to be ready.

Call 1-800-CAR-TEST or 1-614-644-3059.

Since I couldn’t get the monitor to complete I thought I would just get it E-Checked and see what happens. I figured when it failed I would try to explain to them I couldn’t get the monitor to complete and see what they would say.
During the OBDII portion of the test the tester monitor popped up a notice “Manager Approval Required”. The tech call the manager over, he approved the issue, and I passed! Wow, that was easy! The Ohio website said any incomplete monitor would fail the car but I guess the manager can override some? Anyhow, I am happy. Thanks for all of your input.


Thanks for the update

At least you are “smog legal” again

“I thought I would just get it E-Checked and see what happens.”

Please elaborate

Does that mean OBD2 testing and no tailpipe . . . ?

Yes, they just did the normal, non-tailpipe, test.
In Ohio if the car is newer than 1996(I think that’s the year) then they just do the OBDII test, check to see if the catalytic converter is present, and check the gas cap.