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Smog readiness

old skool

Full Member
Joined
Feb 11, 2009
Messages
1,036
Location
Tolleson, AZ
It's time for my emissions test on my avalanche...so I get my bluedriver code reader out to make sure I'm good and I get this...I'm pretty sure It's not going to pass with those readings. Any idea what needs to be done to get it to pass?

IMG-1180.png
 
I have the same reader and TBH I had to go to their website to look up what everything means.  I know if you click on the code it will give you a possible fix
 
I thought if I drove at highway speeds above 55mph for 20 miles, that it would make those ready. That didn't work this time (it has in the past). I might try to get it thru anyway, just to see what happens.
 
old skool said:
I thought if I drove at highway speeds above 55mph for 20 miles, that it would make those ready. That didn't work this time (it has in the past). I might try to get it thru anyway, just to see what happens.
There are certain conditions that have to be met before the tests will run.  Factory info will tell you what those conditions are.
A complete driving cycle should perform diagnostics on all systems. A complete driving cycle can be done in under fifteen minutes.

To perform an OBDII Driving cycle do the following:

    Cold Start. In order to be classified as a cold start the engine coolant temperature must be below 50?C (122?F) and within 6?C (11?F) of the ambient air temperature at startup. Do not leave the key on prior to the cold start or the heated oxygen sensor diagnostic may not run.
    Idle. The engine must be run for two and a half minutes with the air conditioner on and rear defroster on. The more electrical load you can apply the better. This will test the O2 heater, Passive Air, Purge "No Flow", Misfire and if closed loop is achieved, Fuel Trim.
    Accelerate. Turn off the air conditioner and all the other loads and apply half throttle until 88km/hr (55mph) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed.
    Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for 3 minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed.
    Decelerate. Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 32km/hr (20 mph). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.
    Accelerate. Accelerate at 3/4 throttle until 88-96 km/hr (55-60mph). This will perform the same diagnostics as in step 3.
    Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for five minutes. During this time, in addition to the diagnostics performed in step 4, the catalyst monitor diagnostics will be performed. If the catalyst is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst.
    Decelerate. This will perform the same diagnostics as in step 5. Again, don't press the clutch or brakes or shift gears.
 
How are you supposed to perform these instructions unless you are out in the boonies somewhere? Accelerating to 55 mph and coasting down to 20 mph on the freeway is not going to work.  ??? Or, am I supposed to coast down to 20mph in the safety lane? Also, after a cold start, I would have to drive a few miles to get to a freeway to perform the other tasks...is that acceptable?
 
old skool said:
How are you supposed to perform these instructions unless you are out in the boonies somewhere? Accelerating to 55 mph and coasting down to 20 mph on the freeway is not going to work.  ??? Or, am I supposed to coast down to 20mph in the safety lane? Also, after a cold start, I would have to drive a few miles to get to a freeway to perform the other tasks...is that acceptable?
Yep, finding a place to do it is most often the problem.  With a Tech 2 scanner you can force each test to run.  Sorry, that's the problem with clearing codes.  It clears the readiness monitors as well.  Keep in mind that pending problems not yet setting a code can cause the readiness monitor tests to not run as well.  You may not have whatever problem you previously experienced fixed yet.
 
The driving cycle tends to happen on its own and is designed to ensure pretty much all engine conditions are met.

Just keep driving as normal since last reset and I am sure you will meet the driving cycle requirements.
 
2004Slickside said:
Yep, finding a place to do it is most often the problem.  With a Tech 2 scanner you can force each test to run.  Sorry, that's the problem with clearing codes.  It clears the readiness monitors as well.  Keep in mind that pending problems not yet setting a code can cause the readiness monitor tests to not run as well.  You may not have whatever problem you previously experienced fixed yet.
What is most troublesome to me is that the O2 Sensor Heater readiness test does not run immediately.  IMHO this test should run right away.  Seems something is keeping some tests from running.  Here are some conditions that can keep such readiness tests from running (admittedly for Blazer not Avalanche).  I just happened to have easy access to them.  Note that IAT matching ECT at startup within a certain amount is in 2 of the 3 examples.  You might want to start looking there.  Also see if the rest of the mentioned parameters seem reasonable.  Just use your Blue Driver to access the correct PIDs.

Note that these conditions must be met for a specific test to even run.  Has nothing to do with passing or failing the test (that's another set of conditions).

As an example (2004 Blazer)

CONDITIONS FOR RUNNING THE DTC P0440 - Evap

* No active MAP sensor DTCs
* No active TP sensor DTCs
* No active VS sensor DTCs
* No active O2 sensor DTCs
* No active ECT sensor DTCs
* No active IAT sensor DTCs
* DTC P0125 not active
* The system voltage is between 10-17 volts
* The fuel level is between 12.5-87 percent .
* The ECT is between 4?C-30?C (39?F-86?F)
* The IAT is between 4?C-30?C (39?F-86?F)
* The cold start temperature difference (ECT minus IAT) is less than 1.5?C when the IAT is more than the ECT or 8?C when the ECT is more than the IAT
* The BARO is more than 73 kPa

CONDITIONS FOR RUNNING THE DTC P0420 Catalyst

* No active secondary AIR DTCs
* No active CMP sensor DTCs
* No active ECT sensor DTCs
* No active EGR DTCs
* No active Fuel Trim DTCs
* No active IAC DTCs
* No active IAT sensor DTCs
* No active MAF sensor DTCs
* No active MAP sensor DTCs
* No active O2 sensor DTCs
* No active transmission DTCs
* No active EVAP system DTCs
* No active TP sensor DTCs
* No active VS sensor DTCs
* No active misfire DTCs
* The engine speed is 900 RPM or more for more than 35 seconds since the last idle period.
* The engine has been running for more than 346 seconds and the long term fuel trim is stable.
* The predicted catalyst temperature is more than 475?C (887?F) .
* The system is in Closed Loop.
* The BARO is 73 kPa or more.
* The IAT is between -7 to 117?C (20-167?F) .
* The ECT is between 75-117?C (167-243?F) .
* The engine has been idling for less than 60 seconds .
* The actual engine speed is within 100 RPM of the desired idle speed.

CONDITIONS FOR RUNNING THE DTC P0135 O2 Sensor heater

IMPORTANT: This test is void if the system voltage remains outside the specified range for more than 4 seconds .

* The system voltage is between 11.7-17 volts .
* The MAF is less than 27 g/s .
* The engine run time is more than 2 seconds .
* The ECT sensor is less than 33?C (91?F) .
* The IAT is less than 33?C (91?F) .
* The difference between the ECT and IAT is no more than 5?C (9?F) .
 
I had a code p0121 that would come and go. I have a k&n cold air intake that the filter was getting pretty old and dirty, so I replaced it with a brand new one. I then cleared the code out. After that, I had no more problems until...I took my avalanche out for a 20 mile highway drive and was going to take a reading with my bluedriver right after, to see if there were any codes and check the readiness monitors. After I plugged it in, the smog readiness was unchanged and the check engine light came on reading the p0121 code. Drove it home, turned off ignition, waited a few minutes, took another reading. Check engine light had gone out and the bluedriver had no pending codes (readiness monitors still unchanged)
 
old skool said:
I had a code p0121 that would come and go. I have a k&n cold air intake that the filter was getting pretty old and dirty, so I replaced it with a brand new one. I then cleared the code out. After that, I had no more problems until...I took my avalanche out for a 20 mile highway drive and was going to take a reading with my bluedriver right after, to see if there were any codes and check the readiness monitors. After I plugged it in, the smog readiness was unchanged and the check engine light came on reading the p0121 code. Drove it home, turned off ignition, waited a few minutes, took another reading. Check engine light had gone out and the bluedriver had no pending codes (readiness monitors still unchanged)
Remember that the PCM has to actually run a test before it will show a pending code OR change a readiness monitor.  I am suggesting that something is preventing the test from being run at all and that the O2 sensor readiness should run right away after the vehicle is started cold, even without an OBD2 Drive cycle.  A out of spec coolant sensor or intake air temp sensor are a couple of things that have potential to prevent the O2 sensor and Evap readiness tests from being run.  And some readiness tests are taken in order so that could explain the third not being run.  So why not check some of the things that are listed with your Blue Driver, since you have it.

P0121 is a pretty uncommon code.  Throttle Position Sensor.  But problems there have potential to cause the EVAP and Catalyst readiness monitor testing to not complete (see the lists I posted).  You could display the Throttle position (or log it) and drive to see what is happening if anything.
 
I appreciate your help, but when it comes to the technical readings that you are talking about, I'm lost. If you can tell me where to get these readings on the bluedriver menu, I could post them and we could go from there. Thanks.
 
old skool said:
I appreciate your help, but when it comes to the technical readings that you are talking about, I'm lost. If you can tell me where to get these readings on the bluedriver menu, I could post them and we could go from there. Thanks.
Unfortunately I don't have Blue Driver - just know of people who have successfully used the app with their Iphone.  I'm an Android user with the corresponding Android apps like Torque, Car Gauge Pro, and Dash Command.  But I'll see if I can find some stuff that will point you in the right direction.  Shouldn't be very difficult.

Here's the instructions for displaying live data using Blue Driver

https://support.bluedriver.com/support/home
 
old skool said:
Checked again today and the check engine light is back on with the p0121 code again.

For $80 I would just replace the Throttle Position Sensor (TPS) .  It's a start :rolleyes:

https://www.gmpartsdirect.com/oem-parts/gm-throttle-position-sensor-19259452/?c=Zz1mdWVsLXN5c3RlbSZzPXRocm90dGxlLWJvZHkmYT1jaGV2cm9sZXQmbz1hdmFsYW5jaGUmeT0yMDEyJnQ9bHR6JmU9NS0zbC12OC1mbGV4
 
old skool said:
Checked again today and the check engine light is back on with the p0121 code again.
I looked a bit on the P0121 for you, and it seems to be a bit more common than I originally thought.  Almost all cases reported seem to be addressed by either cleaning or replacing the throttle body, after which idle speed is often goofy and kind of out of control.  As I understand it, the cure for the resulting high goofy idle speed is a relearn of some sort done with the Tech 2 scanner (I am not familiar with that procedure).  My factory information ends with the 2005 model year, so I am unable to look up the factory diagnostics for your vehicle.  If you want to know what the factory says about the P0121 (not a valid code for my 2004), then a subscription to AllDataDIY will do the trick.

It's my opinion that if you fix the cause of the P0121 then the monitors will most likely complete.

Good luck!
 
I have manually cleaned the throttle body on every GM vehicle I have ever owned that had one.

I have done this long before I ever heard that people thought you shouldn't.

I am not even sure where those thoughts came from.

Probably from a bunch of heavy-handed guys that should not be left alone to do such things.

I don't know.

I remove the throttle body and the mass airflow sensor and I clean each with the correct CRC cleaner for each.

I CAREFULLY open the throttle plate, hold it open with my thumb and use the cleaner and a clean shop towel to remove every bit of carbon and debris from inside the throttle body bore, including both sides of the throttle plate.

I DO NOT force the throttle plate open, but rather use slow and smooth motions while cleaning the open plate.

I DO NOT allow the throttle plate to snap closed on it's own, but maintain control of the plate and allow it to slowly close fully as needed.

Just over the last weekend, I cleaned both throttle bodies and mass airflow sensors on my newly acquired 2003 Chevrolet Avalanche Z-66 and our 2012 GMC Acadia.

I have NEVER had a throttle body perform badly or had any error codes presented as a result of a good cleaning.

Every time I have cleaned a throttle body, the result was better starting and smoother idle.

I completely replaced the throttle body on my 2004 Cadillac Escalade EXT last year.

The new throttle body bolted right on and never gave me any problems right out of the box.

I had previously looked up the video I linked above before I installed the new throttle body just to be prepared ahead of time.

I did not have to perform any procedure.

I just started the engine and drove off.

Maybe I'm just lucky, but that has always been my experience.
 
Well, this is where I'm at now. I decided to clean the throttle body with some spray cleaner(cleared out the p0121 code), knowing that it may run at high rpms once done. Sure enough it's running at high rpms. Tried the relearn procedure several times. I took it out for a long drive and the rpms settled down at idle. But as soon as I turn it off and start back up, it's back to high rpms. The good news is the p0121 code has not come back and some of the readiness monitors have completed. I think all I need is one more to complete and it should pass emissions. I've got a mobile mechanic that's going to charge me $175 for diagnostic and relearn.

IMG-1183.png
 
Just a quick question, why not just try and run it through before you pay for a mobile mechanic to come out?
 
old skool said:
Although it may or may not pass, that still won't solve the high rpms issue.

Tracking.  I assumed you were up against a wall to get the testing done....I know that's my problem.  I put stuff off :laugh:
 
Loggie said:
Tracking.  I assumed you were up against a wall to get the testing done....I know that's my problem.  I put stuff off :laugh:

I'm hoping I've solved the p0121 code issue with the cleaning of the throttle body. Once I get the rpm issue taken care of, I'll only have the smog readiness to deal with.
Yeah, I waited almost to the last minute, not thinking I would have this much of a problem.

I've also decided to take it to the dealership for the tb relearn...Cheaper than the mobile mechanic.
 
old skool said:
I'm hoping I've solved the p0121 code issue with the cleaning of the throttle body. Once I get the rpm issue taken care of, I'll only have the smog readiness to deal with.
Yeah, I waited almost to the last minute, not thinking I would have this much of a problem.

I've also decided to take it to the dealership for the tb relearn...Cheaper than the mobile mechanic.
Sounds like you're on your way if the P0121 is fixed (and I think that it may be fixed by cleaning)!  FYI the Evap monitor is always the last one to clear and this one only runs after a cold start.  Make sure you keep fuel level between 12.5% and 87% of full (half tank is best).  Also don't expect the test to run unless ambient temp outside on cold startup is between 39?-86? and the ECT sensor agrees with the IAT sensor within specified range  (Info I previously posted).  This you could check with your Blue Driver.

good luck!
 
Took the truck to the dealer this morning for the rpm issue and $140 later, I got that fixed. While I was out, I plugged in my bluedriver to take some readings and to my amazement all smog checks except one (evap) was in the green. So I headed to the emissions station and happy to say, it passed. Truck seems like it?s running a lot more smoother also. Thanks to everyone that gave helpful information. (y)
 
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