OBDII "Not Ready" for SMOG TEST

bsmall2800

bsmall2800

New member
Feb 24, 2010
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Elk Grove, Ca.
I have a 2020 GMC 3500 Duramax and went to get it smog check. The guy said that my OBDII is "NOT READY" . He asked if the batteries or any work done on the truck lately. No to both. He said drive it around for about 100 miles and hopefully things will reset and able to complete the Smog Test. I drove is for about 50 miles and he checked and said its still Not Ready to complete the Smog Test.
I was just wondering if anyone else has experienced the same issues and what you did to make the engine ready for the Smog Check.
Thanks in advance!
 
darkness

darkness

Well-known member
Jul 15, 2009
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vegas
Check your cigarette lighter fuse. I don’t know if they still get power for the obd2 plug from there. If they even have those anymore.
 
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455buick

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Mar 1, 2015
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I'm assuming he's meaning that the emissions systems readiness monitors aren't "ready". Some of those monitors take a very long time to meet their criteria to be "ready". I think the line for that smog test would be miles long if they require the vehicle to have every readiness monitor "ready", but if the line were that long some of the readiness monitors would not be "ready" by the time of the test. Depending on application, some people don't ever hit some systems to "ready". Just my speculation though.
 
2004LB7

2004LB7

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Dec 15, 2010
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I'm guessing at least one monitor not ready too. If I remember correctly, I think one of them is actually call OBD monitor. Each monitor has it's own requirements for passing. Some require one or more "cold" starts while others need to see specific driving conditions.

The typical GM drive cycle that will clear most readiness monitors if nothing is wrong:

Start the vehicle from a cold start. The time to do this is if you have not driven the vehicle for a few hours and the engine coolant temperature is less than 50 degrees F.
Let the engine run on idle. Turn the A/C and rear defroster on. You are trying to apply electrical load to the system.
Accelerate to 55 mph.
Hold a steady speed of 55 mph for 3 minutes
Let go of the accelerator and coast until the vehicle hits 20mph. Don’t apply brakes to slow down.
Accelerate again until 60 mph.
Hold steady for 5 minutes at 60mph for 5 minutes.
Decellerate (coast to slow down).
You may need to repeat steps 3-8 a few times
 
2004LB7

2004LB7

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Dec 15, 2010
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I think on the newer rigs, Nox sensors and oxygen sensors are the biggest reason for readiness monitor issues. And they don't always set codes until they get bad enough
 
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