I have a 1996 Explorer 4.0l with 124,000 miles and it is giving 2 codes.
P0133 Upstream Heated O2 Sensor Slow to Respond Bank 1

#### OBDII System Checks Incomplete

I dont remember the number for the second code.

I replaced the driver's side upstream O2 sensor and cleared the codes. However, the check engine light is still coming on with the same 2 codes. Engine is running fine otherwise in fact these codes dont seem to affect driving at all. I would just like to get that light to stay off!

Thanks,
Brett Molaison

 

If by clearing the codes you disconnected the battery, then that is why you are getting the "OBD-II tests incomplete". You have to go through a complete driving cycle to clear it. Your owner's manual will describe what a complete driving cycle is. Basically it is starting out with a cold engine (less than 80F), driving about 10 miles of city and 20 miles of highway, then cooling off back to ambient. There are several things the OBD-II tests each time you start your vehicle. Some of them must be done when everything is cold. The heated exhaust oxygen sensor test is one of them. Until you have completed the driving cycle, it will stay. It is not the cause of your check engine light. The cause for your check engine light is because you replaced the O2 sensor on bank 0 (driver's side) instead of the faulty one on bank 1 (passenger side). Once you have replaced it and cleared your codes the light should stay off, unless the code is for something else that makes it think it is the O2 sensor.