I just purchased a 2006 XC90 and when taking it to get smogged, the car "main computer wouldn't read". I've heard something about needing to drive the vehicle a certain amount of time/RPMs in order for it to register. Anyone else have the same issue and if so.....what is required to pass?

 

Are you sure it was main computer won't read vs system not ready? Not ready refers to the drive cycle being needed. If it's won't read, you got more problems than not ready. If it is not ready then whoever you bought it from cleared the codes or battery was changed/disconnected and it needs a full drive cycle.

Drive cycle:
Start with the vehicle cool, below 122 degrees F.
Turn off the air conditioning.
Select a location where the driving can be done without violating traffic laws and you can stop safely at the side of the road.

1. Start the engine and accelerate to approximately 1500-2000 rpm.
2. Drive for 6 minutes at 1500-2000 rpm.
3. Stop the vehicle and remain at idle in drive for 70 seconds.
4. Accelerate to at least 45mph and drive for 5 minutes at 1800-2200 rpm.
5. Stop the vehicle and remain at idle in drive for 60 seconds.
6. Accelerate to at least 45 mph and drive for 4 minutes at 1800-2200 rpm.
7. Stop the vehicle and remain at idle in drive for 60 seconds.
8. Park the vehicle and turn off the engine.

 

+1 on ChopperMan's reply. The OBD2 tells the tester when the car is in "ready mode" which means the diagnostics that rely on data samples over time have a full set of data. (some codes are "long term" ). This is why you have some codes that clear and reset after 50-100 miles. The driving cycle described is designed to get all that data into the ECU's memory in an efficient manner. Caution here is, you may wind up seeing a code reset so you'd need to work that should it happen. It also means that for the most part, you can't simply clear your fault codes just prior to an emissions test to make them not appear...

 

I believe you are correct. Pretty sure the term used was system not ready. I will try all those steps and give it another try. Thanks for the info.

 

Would all these required steps need to be performed just prior to (on the way to) having the smog check performed, or rather would need to be done anytime in advance of it being done?

 

They only need to be done after codes are cleared or battery replaced AND you happen to need a smog test. Typically it will become "ready" just by normal driving but takes a long time. The drive cycle is how to expedite that process.