So my check engine light came on my 90' Tracker, I read the codes using a jumper and came up with '13'.  According to the Chiltons manual, a 13 means a faulty heated oxygen sensor.  The book gives no discription of what that is.  I'm guessing that its refering to the O2 sensor, but I'm not ttally sure.  Can someone please confirm this for me?

I don't think the 90' had a heated O2,
which is a 3 wire, I bet it's just a bad O2.

My FSM says code 13 = oxygen sensor circuit (signal voltage doesn't change). So it could be a duff connection or a faulty sensor.

OK, I'll check the O2 sensor.  That may explain the slight gain in fuel consumption too.  The one thats on there is about 2 years old.  I think I remember seeing a way to check it, but I don't think I have the right kind of muntimeter.  

It should read between .2 and .8 Volts.
If it's a Bosch, they had some bad O2
Sensors about then, I got one too,
save yourself all the trouble and just
replace it.

Wild

The 3 wire sensor is a heated sensor.  Only difference is it doesn't have a signal ground, it grounds through the manifold.  The 4 wire sensors have a separate ground that goes back to the ECM for better accuracy.

MEDEL514 , HOW'D THOSE HUBS WORK OUT FOR YA   HAVEN'T SEEN YA ON HERE IN A LONG TIME FIGURED YOU SOLD YOUR RIDE ........MATTY D.  

Those hubs work great!  in fact, I was just out today in the mud since we've been getting rain this past week.  

I checked the O2 sensor and the electrode was demolished.  So yeah, that was what caused the check eng light, plus the gasket on my header was starting to go so I repleced that as well.