My SES light came on and I went to Autozone to get it checked. P0138 & P0139 codes, the guy was really vague and told me "It's the oxygen sensors." Do I have to replace them? Is the Bosch univeral ones good?(the Autozone guy suggested these) Also can anyone tell me how to replace these or give a link? Thanks for any help.

 

P0138= Downstream O2 sensor maximum voltage monitor fault.
P1039= Downstream O2 sensor ciruit slow reponse fault.
Yes, it is time to replace your Downstream O2 sensor. This is the 3rd O2 sensor located before the Cat. Note that the wiring harness goes through the floorboard; pull the grommet out to locate the electrical connector.
I have chose to go with Denso O2 sensors on my '99 they are cheaper than OEM and Denso speacializes in Japanese auto parts. http://densoaftermarket.com/

 

So the two codes leads to only one O2 sensor needing to be replaced? Also can anyone tell me the exact place of the sensor plug? I'm not familiar with the term grommet. Thank you for your help Trajiksmax.

 

The gromet is what protects the wire harness from water etc. The O2 wire runs through the gromet and is located in the floorboard. Remove the gromet with a flat head screw driver, Pull on the wire gentely and the harness should come right out.

 

Wait is the Downstream O2 sensor before or after the cat? In this: http://www.courtesyparts.com/A32_O2-sensors.htmlit looks like for 97+ it's after the cat.

 

:Yes, your right I'm wrong. The Downstream O2 sensor is located at the outlet of the cat.

 

When I replace it, does the SES light go off or do I have to get it reset?

 

You will have to get this reset. I brought mine to AutoZone and had some kid reset it. This might fail, I brought it to a different one and the said, "It is against the law." Or you can just reset it manually on the ECU. Happy Motoring!!!