got codes read, all four o2 sensor

[erskine]

got codes read and it said all four o2s were low voltage. im sure they were never changed and its has a 120k on it and i bought it a week ago.

 

[aldive]

Check upstream of the O2 sensors; something is triggering them.

Good luck ....

 

[glfredrick]

Al is right... If they are reading, then you have another problem upstream.

Best to get past the codes and see what the actual numbers are. Find someone with a Snap On scanner and hook it up. It shows real-time numbers, not just codes.

Parts store code readers are made to sell parts, and codes are only the first part of a diagnosis. A fault code doesn't necessarily mean a bad part, only a reading that is outside the tabled parameters of the computer.

 

[budwich]

as indicated could be a sign of "trouble" up front.... leaks in the intake area. You might try and pull one (one that is easy to get at) and see if it is "contaminated".... might give you some clues.

 

[rumble00]

It wouldn't hurt to change them out anyway, at the mileage you never know.

 

[ThePhoenix]

yes it would hurt to change them out ....it very expensive if you aren't doing them yourself.... :thumbdwn:

I have same issue...3 O2 sensors a week after I bought it. I am going to find the problem, not just throw money at it. I have a code reader coming with a friend tonight hopefully.

 

[fraxinusalba]

Could also just be some oxidation at connector to wiring harness. Happened on my 97 and simply unplugging/plugging the connector a couple times solved the problem. As stated above, good idea to check one of the sensors to be sure they are clean. Left front is probably easiest one to get to - both sensor and connector. Warning - that right front connector is a PITA. You'll have to access it through the fender well.

 

[glfredrick]

Again...

No "code reader" will ever (repeat, ever) be able to diagnose a bad O2 sensor. All a code reader can do is tell you that a reading coming from the O2 does not match the table built into the PCM.

In order to actually diagnose an O2, you will need to test the electrical propeties of the sensor with the proper equipment (a digital square wave multi-meter).

An engine "scanner" will aid in the diagnosis, as you can see real-time engine numbers such as fuel trim, spark, etc., plus the actual O2 readings, which will allow the savvy tech to figure out if the O2 is actually bad or not. Most are not... They last forever unless oiled down by by-passing rings, etc., or by some additive in the fuel.

Hope this helps.

 

[ThePhoenix]

yeah, I am hoping to find something Upstream that will indicate why the readings on the O2 sensors are different...

 

[rumble00]

Forgive me I typed to quick , you do need to get the upstreamed checked before replacing the sensors. And as for it not "hurting", I assumed that you would be doing the change out yourself if you get the right tool.