Long time lurker,first time poster. Lots of good info here, I have a '99 Cherokee SE 4x4 4.0 I changed the up stream o2 sensor a few months ago, and recently CEL came on, checked for the code and got P0131 so I changed the down stream sensor, cleared it but it came back the next day. It idles smooth and run fine and it has the original cat. Thanks in advance.

 

P0131-1/1 O2 SENSOR SHORTED TO GROUND

O2 SENSOR SIGNAL CIRCUIT SHORTED TO GROUND

O2 SENSOR SIGNAL CIRCUIT SHORTED TO SENSOR GROUND CIRCUIT

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Examine the O2S wiring as it leaves the fuel injector wiring manifold and travels over the intake manifold down to its connector.

There have been cases where the O2S wiring in this area has chafed throught the loom to the wiring and it has shorted together or to the intake mnfold.