O2 sensor frustration

[Brit]

I recently rebuilt the trans in my '98 mountaineer. (5.0 AWD) Found out I had O2 sensors hooked up wrong and got that corrected. Now I'm getting a code saying bank 1 sensor 1 has a "heater circuit malfunction". Local dealer said that O2 sensor may still be good but something else is giving the prob. They told me it was the front sensor in pass. side pipe. I originally had left pipe sensors hooked to green plugs and right into blue. Was told that the green plugs are for the front sensors and the blues are for the rears. Anyone have any idea of how to get this straightened out?

 

[section525]

Do you know if you have the two rear blues on the correct sides? I don't know if it matters all that much (I imagine it would). Here is a photo:


Also, you've reset your computer, right?

 

[Brit]

Looks correct to me. Just hate to spend $50 on an O2 sensor that might not fix the problem. Trying to nail it exact. Thanx for such a great pic! Very helpful! By the way, yes, codes were reset but c.e. light comes on after just a couple of miles.

 

[falls guy]

Put your volt meter on each o2s one at a time after the truck is good and warmed up the volts should fluctuate from 0.1-0.9 volts, as you rev the engine. The vehicle must be at running temp for this test. If the volts don't fluctuate with the rpm's, then it is no good. There are 2 different types of 02s's, upstream and downstream. one makes the truck run bad and the other will throw the light on, but cause no symptoms.

Good luck!

 

[Glacier991]

The 02 sensor outputs voltage based on exhaust parameters which can then be used to "tweak" the air fuel ratio. The "ideal" A/F of 14.7 to 1 corresponds to .445V on an O2 sensor output (except exotic titania 02 sensors which Ford does not use). Output voltage should vary and "crossover" that value several times a minute. Until the sensor gets warmed up, the engine does not use the sensor input... this is called open loop. Once the sensor is warmed up, he computer switches into "closed loop" and starts regulating a/f based on that 02 voltage input. To speed up that process later sensors have a built in heater, which operates until the sensor comes into closed loop operation.

The wiring to the heater on that sensor coud be chafed or shorted, a fuse could be blown, or the heater part of the sensor itself could be bad. Start by checking for 12V on the wire for the heater...

As the sensor will heat up eventually even without the heater, this is not a driveability issue.

Hope all this helps.