Emmisions system readiness help

[bmuir]

I have to go get an emissions check on my truck next week, so I checked the system readiness tests and both the 02 sensor and Evap tests show not ready, and i'm sure with both of these on I will fail. Is there a way to get rid of the not ready?

I don't know why they are both in not ready either? I just changed a bad bank 1 02 sensor, checked the gas cap and looked at the evap system and everything looks ok. What are my options for passing the test, and checking the evap system to figure out whats casuing to to say not ready.

thanks!

[Taz]

Hello Brian,

Did you happen to have a DTC set recently ? Did you plug a scanner into the vehicle and hit the clear DTC button recently ? Did you reflash the tune recently ?

If any of these scenarios is the case, and the vehicle is mechanically OK (no EVAP leaks, etc.) then the "readiness" will occur after a specified number of DTC free drive cycles - can't remember off the top of my head how many drive cycles your 2001 Sierra requires to enter "readiness" - can try and look that up if it makes a difference to you.

Good luck ...

Regards,
Taz

[bmuir]

DTC the other day of p0440..this is probably why the evap is "not ready". It usually takes a while for p0440 to come back after being reflashed. I also just reflashed the tune, right after I put the new 02 in 30 mins ago. Just went for a drive and the 02 readiness is now fine. I should be able to pass emissions with just the evap on, provided I dont throw a PO440, correct? I should also figure out the P0440 just to fix that..but where should I start?

thanks for the help Taz!

-Brian

[Taz]

As you probably already know, P0440 is a generic EVAP code. P0442 indicates a small leak detected. There are numerous other specific EVAP DTC.

The PCM tests the EVAP system for:

large and small leaks
excess vacuum
purge flow during non-commanded conditions
fuel level and fuel pressure sensor faults
EVAP purge and vent valve faults

Check:

loose / defective / non-sealing gas cap
EVAP purge lines
obvious component damage
Schrader valve - loose or damaged cap

The most common cause of a P0440 DTC is the gas cap. Take the gas cap off, and check the top of the fuel filler neck for rust and / or corrosion – if present clean and “level” the area (medium to fine sandpaper works great) – follow up with very fine sandpaper or a scuff pad.

Buy a new gas cap. When you install the gas cap after a fuel fill, make sure you hear half dozen ratcheting type “clicks” – these are supposed to self torque, then ratchet – but often they need a little extra help !

Good luck ….

Regards,
Taz

[n8dogg]

I am not sure about the emissions standards in your area. But in New York State (Upstate) you are allowed one monitor not ready for 2001 and newer vehicles. Fortunately Evap is usually the last to set so you can get away with it if you time it correctly.

[Chevy366]

Same here , one will pass , but a tripped DTC will not , can't have MIL light on , don't know about "pending" cue for DTC though .

[bmuir]

Ok, thanks guys. I do get the MIL for P0440, but it takes a while to show up. Ill just clear the check engine light before I go and make sure I only have the 1 system readiness issue.