I haven't had any issues with the car for over a year, no CEL and no messing with the computer or sensors, but still the OBD check came back unready/incomplete causing it to fail smog.

Following this I scanned and have no codes, no issues whatsoever.

The battery has not been disconnected recently either, so a loss of power to the computer is not a factor.

Any thoughts as to why the computer is not coming back ready after all this time? I thought it would clear/become ready after driving some following maintenance. Anything I can do about this?

 

It sounds like the cpu is not communicating to the sensors due to a short or a break in the harness or the ecu is not for this vehicle. example the car is a federal emissions and you have a cali emissions ecu. Their is something wrong with your car. The car comes up not ready when also the ecu was reseted with a scanner or a consult like scanner.. Check all the connections and harness wires breakage and sensors and fuses that have to help with the ecu and communications line.

 

Thanks, will check thoroughly for bad connections. It couldn't be the wrong computer because I haven't changed the computer and it has passed the last two times.

Is it possible that damage to the computer could cause this also? Because for a while I did have a bad diode in the alternator causing it to put out A/C on the whole electrical system.

 

To follow up, this has been resolved. Mechanic found that the specific monitors that weren't becoming ready were all emissions related and so suspected the rear cat was the root cause, even though it didn't have any codes.

This turned out to be right, replacing the cat got all the monitors to become ready.

It also had high hydrocarbons with no other obvious cause so the cat was definitely going out.