I have a 2003 Suburban 1500 with 130K miles. I cannot get my emissions done because it fails "Readiness" due to 2 monitors that do not complete.

They are the Evap Sys Monitor and the Oxygen Sensor Monitor.

My battery has not been disconnected in about 6 months and I have no trouble codes active or pending.

So far I have put in new spark plugs and new oxygen sensors, but no change in status. Also I have spent a couple weeks trying to complete every "drive cycle" I've ever heard of with lots of cold starts, lots of highway speed driving etc.

Any thoughts on why these monitors will not complete?

 

Same problem with my 2003 Chev Silverado.

Engine light came on & code indicated the upstream O2 sensor was bad. Replaced both upstream 02 sensors & have the same problem with the "not ready."

Came here hoping to find answer.

 

After 2 months now, I finally figured out the problem. I had previously changed spark plugs and all 4 O2 sensors. Never got the Evap or O2 sensor monitors to complete and therefore couldn't pass emissions here in GA.

The problem ended up being a weak battery. Just barely weak. It cranked up fine with no hesitation, but the battery voltage was dropping down to 9.3V during the short crank. A couple of GM folks told me that it has to stay up or it will mess up the monitoring parameters. I believe it was stay above 9.6 or 10.6 volts while cranking for up to 15 seconds.

Put in a new battery and drove it for 4 days and the Evap Sys Monitor moved to ok. Still waiting on the O2 sensor monitor, but in GA you can run the emission test with 1 incomplete.