How do I get my OBDII I/M monitors "ready"?

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jcardona1

jcardona1

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I had an O2 sensor DTC pop up and I cleared the ECU using my scanner. This was several weeks ago and a few hundred miles. Today I checked the I/M Readiness using my Torque app and it's still showing a few monitors not being ready.

Is there a specific drive pattern I should follow to get these ready? I checked the FSM and couldn't find anything on how to get them ready. Any ideas?

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yes, there is some pattern to it to get it done quick. This was described here someplace and I thought was in the FSM. I discussed related issues here some time back. There may be some info there.
But anyway, several weeks and hundreds of miles of normal driving should be plenty, unless you're driving at crawling speeds all the time . There is likely something else going on / not right.
 
Ok just got back from doing these drive procedures 2 times and still nothing. The 2 monitors still show up as incomplete. The FSM doesn't really tell you what to do when it's still showing not ready. Could there be a problem with my ECM? Here's the chain of events that have led up to this:

- After a 3hr road trip I get a check engine light pop up (MIL)
- Hook up to code scanner and see it's P0136 (O2 Sensor Circuit Malfunction Bank 1, Sensor 2)
- Clear all codes with code scanner
- Order a new O2 sensor (not installed yet, waiting on it to arrive)
- About 300ish miles later I check to see the status of my monitors and see Catalyst and O2 Sensor are not ready
- Go through the drive procedures today per the FSM and nothing


Back to my O2 sensor. I used my Torque app to check the output voltage of the 2nd O2 sensor and it looks like it's fried. The voltage barely changes and is very out of spec per what the FSM says it should be (0.4v or less ~ 0.5v or more). Could a bad O2 sensor do something to the I/M monitors?

Help? Anybody!

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jcardona1 said:
Could a bad O2 sensor do something to the I/M monitors?
Click to expand...

Yes

Why don't you fix the known problem and not worry about the I/M monitors?

They won't set as ready until the computer feels that everything is AOK
 
86tuning said:
Yes

Why don't you fix the known problem and not worry about the I/M monitors?

They won't set as ready until the computer feels that everything is AOK
Click to expand...
Yeah, just as soon as the new O2 sensor arrives! But I'm still curious as to why the monitors haven't shown as ready. Wouldn't that indicate a potential problem somewhere? If there's an issue somewhere (like my bad O2 sensor) the CEL won't turn on and you'd never know you have an issue since the car isn't monitoring itself. All the while you're probably suffering from poor performance and abysmal gas mileage.

I'd like to get an understanding of what causes the OBDII monitors to not be ready.
 
Assuming the vehicle you are testing is an FZJ80 (you did post this thread in the 80's section after all). The front heated oxygen sensor is used by the ECM to sense exhaust oxygen content and control fuel trim. The rear heated oxygen sensor reports the exhaust oxygen content after the catalytic converter. The "catalyst monitor" OBD-II test is based on an observed correlation between conversion efficiency and oxygen storage capacity of the converter, and is calculated based on the ratio of front and rear O2 sensor voltage waveform "crossings." But the catalyst monitor test can't be run if the ECM is not getting good data from both O2 sensors. Since you have a bad O2 sensor (as indicated by the incomplete O2 sensor test), then the catalyst monitor test is never run and thus shows up as incomplete. So it's very likely that other than the bad O2 sensor you've discovered, there's nothing else wrong with your vehicle.
 
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TrickyT said:
Assuming the vehicle you are testing is an FZJ80 (you did post this thread in the 80's section after all), then your Torque app is giving you bogus results. There is no catalyst sensor in the FZJ80, so this test should be reporting "Not avail." And on the FZJ80, I don't think it's possible to get an Incomplete test on an oxygen sensor, so this test result seems wrong too. The only test where you will get an Incomplete status on an FZJ is the EGR system test. The driving pattern described in the FSM clears Incomplete for the EGR system only. So it's very likely that other than the bad O2 sensor you've discovered, there's nothing else wrong with your vehicle.
Click to expand...

Thanks for the info! Yes, it's a 96 LC. But if what you're saying is correct, that means my handheld scanner is bogus too...? I just hooked it up and it's showing not ready as seen by the yellow light and the blinking C and O monitors (they're lit up faintly because they're flashing).

Any ideas now?


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jcardona1 said:
Thanks for the info! Yes, it's a 96 LC. But if what you're saying is correct, that means my handheld scanner is bogus too...? I just hooked it up and it's showing not ready as seen by the yellow light and the blinking C and O monitors (they're lit up faintly because they're flashing).

Any ideas now?
Click to expand...

Have you replaced the bad O2 sensor yet? The ready/not-ready signal comes from one bit being set or clear in each of the OBD-II PIDs. If you know you have a bad O2 sensor you need to replace it. The FZJ ECU uses data from both O2 sensors to perform catalyst efficiency monitoring.
 
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TrickyT said:
Have you replaced the bad O2 sensor yet? The ready/not-ready signal comes from one bit being set or clear in each of the OBD-II PIDs. If you know you have a bad O2 sensor you need to replace it. Maybe the FZJ ECU lets the second O2 sensor double as a catalyst monitor too. I.e., one sensor but it throws two codes.
Click to expand...

Not yet, still waiting on it to arrive. I was just concerned about the monitors not being ready. Because they were obviously working when the P0136 code was thrown a few weeks ago. And now they won't turn back on.

I'll update this thread once the new sensor is installed :)
 
Most vehicles will test emission components in a certain order. When your vehicle is getting to the O2 sensor monitor test it is seeing that the component is not working properly. Some vehicle will immediately complete the monitor and just set the O2 sensor code, then your MIL will come on.

However, some vehicles will see a problem and continue to re-test the faulty component before it sets a code. Especially if the test results are borderline. In this case you will usually have a Pending code stored (soft code) without the MIL on and no (hard code) set.

Once you have repaired the problem all your monitors will most likely set within 100 miles...:hillbilly:
 
Oh yeah........if you REALLY never want your monitors to be incomplete, then just don't clear your data with the scan tool. If you get a code and properly fix the problem, the stored fault code and MIL light will clear on there own. Plus you won't loose valuable freeze frame data.
 
Thanks, that was helpful! So a question on how these OBDII monitors work. Even if it's showing as 'not ready', are they still actually monitoring anything? If a particular monitor isn't on, how does that affect the rest of the vehicles programming inside the ECU? Like with this O2 sensor for example. Because the monitor is showing as not ready, does the computer actually know the sensor is bad? Is the computer able to do anything with the air/fuel ratios?
 
jcardona1 said:
Thanks, that was helpful! So a question on how these OBDII monitors work. Even if it's showing as 'not ready', are they still actually monitoring anything? If a particular monitor isn't on, how does that affect the rest of the vehicles programming inside the ECU? Like with this O2 sensor for example. Because the monitor is showing as not ready, does the computer actually know the sensor is bad? Is the computer able to do anything with the air/fuel ratios?
Click to expand...

Even with a monitor in (not ready) or (incomplete) status, the computer is always continually checking certain components and some only when the right driving criteria are met.

The computer knows the status if everything it is watching or testing...when the computer sees a bad O2 sensor it just sets the code and turns on the MIL. It will continue to adjust fuel trims according to the data received from a good or bad sensor.

Now for example if the computer sees there is a severe mis-fire, it will flash or turn on the MIL and actively adjust fuel trim to prevent any damage to other components (like the catalyst).

"Not-ready" just means the computer does not have conclusive (or final) test results for that component or system.
 
TYM4FUN said:
Most vehicles will test emission components in a certain order. When your vehicle is getting to the O2 sensor monitor test it is seeing that the component is not working properly. Some vehicle will immediately complete the monitor and just set the O2 sensor code, then your MIL will come on.

However, some vehicles will see a problem and continue to re-test the faulty component before it sets a code. Especially if the test results are borderline. In this case you will usually have a Pending code stored (soft code) without the MIL on and no (hard code) set.

Once you have repaired the problem all your monitors will most likely set within 100 miles...:hillbilly:
Click to expand...
You're right about how the Toyota's work :) Per the service bulletin I linked above:

The readiness status may not switch to “complete” after the first drive pattern trip if a
Pending Code has been set (first trip for a two–trip DTC).
- Pending Codes are available from the DTC Info Menu in Enhanced OBDII.
- Pending Codes indicate a POTENTIAL problem was detected. A second trip is
needed to confirm the DTC prior to diagnosis.
- Once a second trip is completed, a current DTC will be stored.
Click to expand...

That explains why my monitors aren't showing up as ready.
 
:cheers:
 
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