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Thread: ? for OBD2 smog experts

  1. #1
    Senior Member DonTom's Avatar
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    ? for OBD2 smog experts

    If I get a check engine light for a single OBD2 code and erase it with and OBD2 reader, does it only put that one sensor to a temporary "not ready" condition or does it put all sensors to a temporary "not ready" condition?

    -Don- SSF, CA

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    I think it depends on the car and version of the software.

    Getting ready to pass the CA DMV emissions inspection?

    Chip H.

    Former owner: 2012 Honda Civic LX, 2006 Honda Ridgeline RTL, 2000 Honda CR-V EX, 2003 MINI Cooper S, 1992 Honda Accord LX, 1999 Mercedes ML-320, 1995 VW Jetta GLX, 1991 Mercury Capri XR2, 1981 Mercury Zephyr, 1975 Chevrolet Impala

  3. #3
    Ridin Dirty dom's Avatar
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    What it does is erase the code.

    If the sensor reads that same fault again the code re-appears.

    There is no such thing as temporary "not read" condition that I know of.

    If so we'd able to program our cars as we like.

    Government doesn't like that shit.

    What is the code you're getting?

    "Tutto nello Stato, niente al di fuori dello Stato, nulla contro lo Stato "
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    Senior Member DonTom's Avatar
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    Quote Originally Posted by dom View Post
    What it does is erase the code.

    If the sensor reads that same fault again the code re-appears.

    There is no such thing as temporary "not read" condition that I know of.

    If so we'd able to program our cars as we like.

    Government doesn't like that shit.

    What is the code you're getting?
    You're nor familiar with "not ready". If you clear a code (or change your battery) you cannot go for a smog test right away. It will not fail, but the smog test will be "rejected" because the car has not been given enough time for the codes to set. So you have to be tested again later which is almost the same as failing, as you have to come back and be resmogged.

    Normally, a few days of driving will get all codes "ready" for testing. Also the car must be started from a very cold (such as overnight) start.

    There is no way to cheat a OBD2 smog test. If you clear a code, you must drive it enough to get the code again if there is really a problem. If the vehicle has not been driven enough to give time for the code to turn on the "check-engine" light if there is a real problem, the car will be "rejected" from testing.

    -Don- SSF, CA




    To

  5. #5
    Senior Member DonTom's Avatar
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    Quote Originally Posted by chiph View Post
    I think it depends on the car and version of the software.

    Getting ready to pass the CA DMV emissions inspection?

    Chip H.
    I wonder if it can depend on the OBD2 reader. Here's what happened. 1997 Sebring Convertible, 2.5L. I got a code P0125 (Insufficient Coolant Temperature For Closed Loop Fuel Control) which was caused by low coolant level from a leaky radiator cap. I cleared the code with my OBD2 reader right away and refilled the coolant and replaced the radiator cap. All okay, no check engine light. I then drove the care for around 50 miles but I did NOT start from a cold start (my big mistake). I then went to get a NV smog test (this car is normally kept at my Reno home). I was rejected because THREE codes were "not yet ready for testing".

    So I drove the car another 100 miles and from at least one very cold start the next day. I then went to get a NV smog test again. Still had one code "not ready", but fortunately, in Washoe County (Reno) they allow two codes to not be ready on vehicles older than year 2000. They only allow one to be "not ready" on vehicles newer than year 2000. So I passed the test.

    -Don- SS, CA

  6. #6
    Senior Member grouch's Avatar
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    Quote Originally Posted by DonTom View Post
    I wonder if it can depend on the OBD2 reader. Here's what happened. 1997 Sebring Convertible, 2.5L. I got a code P0125 (Insufficient Coolant Temperature For Closed Loop Fuel Control) which was caused by low coolant level from a leaky radiator cap. I cleared the code with my OBD2 reader right away and refilled the coolant and replaced the radiator cap. All okay, no check engine light. I then drove the care for around 50 miles but I did NOT start from a cold start (my big mistake). I then went to get a NV smog test (this car is normally kept at my Reno home). I was rejected because THREE codes were "not yet ready for testing".

    So I drove the car another 100 miles and from at least one very cold start the next day. I then went to get a NV smog test again. Still had one code "not ready", but fortunately, in Washoe County (Reno) they allow two codes to not be ready on vehicles older than year 2000. They only allow one to be "not ready" on vehicles newer than year 2000. So I passed the test.

    -Don- SS, CA

    I'm at a loss to figure how codes are "not ready". The codes are fault codes unless California type emissions are different than Federal. Then again, around here, we don't have emissions testing. California does odd things and I noticed when I was out there driving a truck, Nevada plays follow the leader.
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    Senior Member DonTom's Avatar
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    Quote Originally Posted by grouch View Post
    I'm at a loss to figure how codes are "not ready". The codes are fault codes unless California type emissions are different than Federal. Then again, around here, we don't have emissions testing. California does odd things and I noticed when I was out there driving a truck, Nevada plays follow the leader.
    This had nothing to do with California. This smog test was for my 97 Sebring which is at my NV home and has a NV plate.

    Was a NV (Reno--Washoe County) smog test, where I had the "not ready" on three sensors. BTW, right on their tester it will list the sensors that are "not ready". Since I only cleared a single code, I have to assume it resets ALL OBD2 sensors to "not ready". IOW, if I had the smog test right away, it would have shown all sensors as being "not ready" just as if the battery was disconnected and not driven enough.

    OBD2 is smarter than I previously thought. It prevents almost any type of cheating possible.

    But normally, a week of normal driving with set all sensors ready.

    It would be nice if engines had an indicator that will show when any code is not ready.

    -Don- SSF, CA

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    When you clear any codes you also clear all the monitors. These are not codes, they are the tests the PCM runs to check the systems. This is why you have to drive for a while until the monitors have run.

    Bill

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    Senior Member grouch's Avatar
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    Quote Originally Posted by asemaster View Post
    When you clear any codes you also clear all the monitors. These are not codes, they are the tests the PCM runs to check the systems. This is why you have to drive for a while until the monitors have run.

    Bill

    Okay, that makes sense. I got out of auto repair in '84 although I do dabble in later model stuff. My reader will specifically check the monitors if I enter the right command.
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    Senior Member DonTom's Avatar
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    Quote Originally Posted by asemaster View Post
    When you clear any codes you also clear all the monitors. These are not codes, they are the tests the PCM runs to check the systems. This is why you have to drive for a while until the monitors have run.Bill
    That's what I assumed from my experience. I guess there is no way to only clear the single monitor that sets a single OBD2 code.

    Some monitors set before others. It can take about a week of normal driving to get all the monitors ready for testing and that has to include cold starts (overnight cooling) warming up to normal temperature in a single drive.

    The problem can be a simple code that was fixed and then won't pass a smog test because of OTHER monitors not being ready. The same happens when the battery is replaced.

    -Don- SSF, CA

  11. #11
    Senior Member DonTom's Avatar
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    Quote Originally Posted by grouch View Post
    Okay, that makes sense. I got out of auto repair in '84 although I do dabble in later model stuff. My reader will specifically check the monitors if I enter the right command.
    OBD1 wasn't so cheat proof as OBD2 (since 1996).

    You can check a single monitor, but I wonder if any OBD2 code reader or other tool can clear a single MIL code without resetting all the monitors to "not ready."

    It would be nice if we could and also have an indicator of some type when all monitors are ready. Different monitors require much different conditions to set.

    -Don- SSF, CA
    Last edited by DonTom; 04-13-2012 at 09:11 AM.

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    Senior Member DonTom's Avatar
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    Quote Originally Posted by asemaster View Post
    When you clear any codes you also clear all the monitors. These are not codes, they are the tests the PCM runs to check the systems. This is why you have to drive for a while until the monitors have run.Bill
    Is there an owner affordable tool or tester which can tell us when all codes are ready?

    The reason I ask is because I have several of my vehicles in NV and they have NV plates and need to be smog tested there. Sometimes, I only have a couple of days to get it done and I need to know exactly when it's ready for testing.

    Murphy's law last week. I got a check engine light the very morning that I was driving the car down for a smog test. I cleared the code, fixed the problem and drove 20 miles, but that wasn't enough. I had to go back the next day.

    Was a simple problem, code P0125 caused by a leaky radiator cap. Coolant was low. The P0125 means "insufficient coolant temperature for closed loop operation", which means the car is taking longer to warm up than expected.


    -Don-

  13. #13
    Senior Member grouch's Avatar
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    Quote Originally Posted by DonTom View Post
    Is there an owner affordable tool or tester which can tell us when all codes are ready?

    The reason I ask is because I have several of my vehicles in NV and they have NV plates and need to be smog tested there. Sometimes, I only have a couple of days to get it done and I need to know exactly when it's ready for testing.

    Murphy's law last week. I got a check engine light the very morning that I was driving the car down for a smog test. I cleared the code, fixed the problem and drove 20 miles, but that wasn't enough. I had to go back the next day.

    Was a simple problem, code P0125 caused by a leaky radiator cap. Coolant was low. The P0125 means "insufficient coolant temperature for closed loop operation", which means the car is taking longer to warm up than expected.

    -Don-

    My code reader ran me about $250. It's about as deluxe as you can get without going to a dealer tool. Ask over at a parts store that sells them and see if they offer one that can run monitor testing. I got mine at Advance but I see the same one at AutoZone.

    When I got out of auto repair in '84, only late model, high end European cars had computers. We don't have emission testing anywhere near me so I've never bothered with learning the ins and outs of it.
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    Senior Member DonTom's Avatar
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    I just found some good info on not ready here.

    -Don-

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    Senior Member DonTom's Avatar
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    Look what I just found here!

    I just ordered one, but from Amazon.


    -Don-
    Last edited by DonTom; 04-14-2012 at 03:11 AM.

  16. #16
    Senior Member grouch's Avatar
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    Quote Originally Posted by DonTom View Post
    I just found some good info on not ready here.

    -Don-


    Where is the legislation on this one? Nevada? California? A lot of the road laws refered to are quite different in Indiana, where I'm located. Here, if the plates aren't up to date, the car can't be driven. There is an exception for current plates onto another car you just bought if the one the plates are off of is no longer owned.
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    Senior Member DonTom's Avatar
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    Quote Originally Posted by grouch View Post
    Where is the legislation on this one? Nevada? California?
    The link was for Wisconsin, but it sounds exactly like Washoe county, NV, where I keep several of my many vehicles (I one a home in Reno, NV and here in SSF, CA).
    Quote Originally Posted by grouch View Post
    A lot of the road laws refered to are quite different in Indiana, where I'm located. Here, if the plates aren't up to date, the car can't be driven. There is an exception for current plates onto another car you just bought if the one the plates are off of is no longer owned.
    Yes, many laws are different between CA & NV too. Especially smog tests. Here in CA, the smog testing is done live with the car under full load, using a treadmill. They check EVERYHING, OBD connector, tailpipe emissions, no modifications, etc on every vehicle. NV only checks the OBD2 tester, but on large vehicles, such as my RV, they check the emissions on the tailpipe too.

    -Don- SSF, CA

  18. #18
    Senior Member DonTom's Avatar
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    I received my Ready or Not unit. It does quite a bit more than I expected, as the unit is programmable to match whatever state's requirements. For an example, I can program it to sound a beep every 30 seconds when there are zero sensors "not ready" or up to four. IOW, you can drive with it connected after a MIL (Malfunction Indicator Lamp, or "check engine light" occurs and code is erased ) and then it will give a beep every 30 seconds when it's ready for a smog test. It can also be set to beep when a MIL to let you know right away when there is a problem.

    I put it on several of my cars which were all ready. Just turn the ignition on with it connected to the OBD2 connector. I got a green "ready" as well as all six sensors showing green and a beep every 30 seconds.

    So then I connected it to my RV, which got a MIL the last time it was driven. I put on about a 100 miles on it since then (same day), but it is NOT yet ready but that is only because it has not had a cold start since the MIL. Two sensors are not ready. The O2 sensor heater (which makes sense as the car has not been cold started since the MIL) and I also got a EVAP not ready. Can somebody here explain what might get the EVAP ready? IOW, would that need a cold start or a gas tank fill up or what, in order to self-test?

    My RON unit shows my RV as the CAT, O2 sensor and EGR being ready and the "sec air" being N/A (light not lit at all, instead of green or red).

    I assume the next time I start the RV and drive it to a full warm-up, all sensors will be ready. It does need to have a NV smog test within a few weeks.

    The RV is here in SSF right now, so I will have to drive it to my Reno home soon. That should be more than enough to get all sensors ready, as there will be another cold start the next day.

    My biggest fear is that I will get another MIL on the way to be tested.

    Today, I checked the fuel pressure and got a reading of 46 psi. I also cleaned out the MAF sensor and checked for vacuum leaks and such. It had a code P0171 (bank 1 too lean). This code cannot be caused by a bad O2 sensor. This code gets set when the computer is at the end of its range trying to make it richer. A dirty MAF sensor, low fuel presure and vacuum leaks are common causes of such too lean codes.

    Some place on the web I found where it mentioned the normal fuel pressure is 55-62 psi for the year 2000 Express Van 7.4L (which my Class C RV is made from ). Tomorrow, I will change the fuel filter.

    -Don- SSF, CA

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