o2 sensors

1997 FORD AEROSTAR
61,000 MILES
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LDIS43
  • MEMBER
  • 2 POSTS
I have been fighting an issue with random misfire codes and lean bank 1.
the random misfires are from p300, and or most all cylinders they jump around. when I scan it for live data it does not show voltage from 02 sensors or live short or long term fuel trim. It does show fuel trims in freeze frame after code trips. When I unplug the sensors it shows o2 heater circuit. The front sensors has been replaced and shows acceptable voltage when operating with a multimeter. the rear o2 sensor tests lean with multimeter. I am concerned that the computer is not getting the o2 data since my scanner shows no voltage.
Mar 3, 2012 at 5:58 PM
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RASMATAZ
  • ✓ASE Certified Mechanic
  • 75,992 POSTS
  • ASE Certified Mechanic
Lean fuel condition could be caused by one of the following below:

1.Vacuum leaks

2.EGR and PCV valve.

3.Low fuel pressure.

4.Dirty fuel injectors.

5.Mass Air Flow Sensor.

6.Oxygen Sensor.
Mar 3, 2012 at 6:01 PM
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LDIS43
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really my question is more about why the 02 sensors do not read on my scan tool. I know the reasons for lean condition. If the tool does not pick them up I was thinking that the computer is not either and just adjusting without them. It shows 0.00 volts for both sensors on live data and -100 on both fuel trims. The o2 sensors are working but not showing readings on the scan tool. all the grounds are working. Could the computer be bad and not reading both sensors.
Mar 3, 2012 at 7:58 PM
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RASMATAZ
  • ✓ASE Certified Mechanic
  • 75,992 POSTS
  • ASE Certified Mechanic
Could be the computer-check the wiring back to the computer if its open or short if not -have the computer tested-
Mar 5, 2012 at 11:11 AM
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