Hello! I’ve been trying to get my car smogged so I can register it. On the way home from work last week, the day before I was going to smog it, the check engine light came on.
It was for P0442 code. We replaced the gas cap and a clamp on a hose. After clearing the code it hasn’t come on even after a hundred miles of driving, but it won’t show any results for the evap or the oxygen sensor and thus rejects the smog test.
Could the sensor itself be bad?
IF you tend to put as much gas into your tank as you can, in other words, you keep adding after the first click of the handle, you are overfilling the gas tank.
Gas stored in underground tanks is usually around 60°. Once in your gas tank, it is going to the ambient air temperature, which right now is higher. The gas will expand and be forced down your vent lines to the charcoal canister and purge valve. This can cause a temporary malfunction of the purge valve.
The cure for this is to stop filling at the first click.
Now the usual code for this is not the P0442 but P0446 so you may have had a problem with the cap or the clamp you replaced. After clearing the code, the vehicle must complete a number of drive cycles before the system will give a ready light. If it detects the problem during this time period, it may not turn on the light, but it will store a code as a pending code.
If you have a code reader, check for pending codes. If you don’t have any, keep checking for the ready lights, they should come on when the required drive cycles are completed.
Some ready lights require certain conditions be met at least once during the drive cycles. You will need someone with access to the factory service manual for your vehicle, or to alldata to get this information.
Thank you. I’ll see if I can find what conditions I need to meet. I don’t always fill extra after the click but I’m guilty of doing it.
Just an update! I did a full drive cycle to/from work for the last week and it passed the smog with flying colors today. Thanks again for the help!