Temperature needle and CEL help!

Hey guys, been a long time since I've posted. I have two questions.

This evening driving home after work I realized that my temperature needle in the dash of my 01 wasn't working. Even after driving for about 10 miles it stayed in the same position in the picture. I even tried the heater to make sure it wasn't just staying ridiculously cold and it blew normal hot. Any advice on what this may be. Maybe it's just broken inside the dash????

Second, the check engine light came on a few months back reading P0031. So I replaced the O2 sensor. A few weeks later it came back on so I contacted the company I bought the sensor from off eBay and they sent me a new one no questions asked. I threw the old on in and the CEL was clear for about a week then it came back on throwing the same code after the second new o2 sensor. Any idea why this is happening??

 

could be the gauge is bad or the sending unit or the wire for it is bad.

I would use the FSM to run the test procedure to see if the sending unit is working, that's the most likely cause

 

ground your coolant temperature sending unit and see if the needle moves to full hot if it moves the gauge is good and the sending unit is bad you can also ohms check the sending unit for excessive resistance

 

this ^^^^^^^

he means you touch the sending unit wire to a good ground.

all the sending unit does is give a ground connection and the sensor adjusts the resistance based on temp so the amount of resistance to ground is what moves the needle.

 

this is my second time coming across this issue on taco world. 2 things

1, temperature sender is bad or disconnected somehow. easy part.

2, your computer relies on your temp sender to tell it when it's warmed up, otherwise it runs rich forever as a part of the warming up process. causing your cat and exhaust to run to run abnormally. and too much can mess with the o2 sensors probably just like this.

so start by fixing your temp sender and running some fuel system cleaner or cataclean.

 

The temp gauge/sender and the ECU/ECT (engine coolant temp) are two completely different and separate things. The dash gauge/sender has nothing to do with engine management.
On the 3.4 the "gauge" sender is located on the rear of the lower intake between the two heater hose connections. The ECT sender is at the front of the intake just inboard of the end of the pass side fuel rail.

 

This is one of those very common issues that NOBODY has ever fixed - lots of ideas, but nobody has ever said "I figured this one out."

Most people will just tell you to get a scan gage.

My temp gage has been dead for a year as well...

 

just like the guy before me said. get a scan gauge and see what the fuel trims say. everything may just be working fine, just that you may have an issue so extreme it's making your computer think your sensor has gone crazy when it really isn't.