Heated Oxygen Sensor

[rhandwor]

Originally Posted by edd821

Well, that didn't do it. Replaced the rear upstream sensor with a NTK brand but it's still blowing the fuse and giving me a PO 31 & 51 codes. Taking it to a mechanic to check the wiring at the connector. So we'll see.

I would look at the wire feeding the two oxygen sensors. Look for where the wiring could touch the exhaust system. Follow the wires up to the fuse box. Disconnect your battery ground unbolt the relay center and look for corroded wiring underneath where the wires connect. Also check where it goes through the firewall.

[jamx13]

The clue is the word "heated". Is your engine running at the proper temp? If not, try changing the thermostat.

[Thomas Sams]

Dude i think it means the electrical connection on that particular O2 sensor either has disconnected because in my jeep i was also face the same problem or may be connection is need to be clean..

[ThomasKukla]

Has anyone got an idea what the key on (not engine running) voltage should be from fuse #16 under hood in PDC?

I have tried everything to get rid of a P0051 but no luck. I found that when I pull the fuse and check the voltage at #16 that it only puts out about 3.5 compared to the 12 volts in all the other slots.

That is the only thing I can think is causing my P code.

Thanks in advance for any help.

Oh, by the way. 1999 Jeep Grand Cherokee Laredo, 4.0 I6 with Ca. emissions.

[rhandwor]

Without a wiring diagram I can't be sure but I think you have resistance in the circuit. I would disconnect the ground and turn the fuse holder upside down and look for corrosion. If this feeds the oxygen sensor try using an inline fuse holder and a 12 volt feed.