I tested the duty cycle using the X11 diag connection and it showed a rock steady 7.18 Volts. This equates to a 47% duty cycle which is on the slightly rich side. The fact that the voltage never varied pointed to the O2 sensor. I then tested the O2 sensor to see if its voltage varied between .2 and .9 volts and my meter stayed steady at .002-.003 volts (basically zero volts) so the sensor is definitely the culprit. I also checked the O2 heater circuit to make sure it wasn't at fault it showed a solid 14 volts.

I see the street price for the Bosch unit is around $135. A universal 3-wire replacement is only around $42 which is tempting. It doesn't come with the full wire harness with connectors so you simply crimp it to the existing wires. This may actually be a blessing since you don't have to reroute the new cable through the floor pan and into the interior of the car.

T.C.