2000 Expedition 5.4 throwing codes for all 4 o2 sensors. Sensors already replaced and still throwing code
- Thread starter giuliandi
- Start date
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According to the OBD SysOp manual, those faults happening immediately after starting the engine indicate a voltage problem. As it's occurring on all four circuits, maybe there's a common power source to blame.
Hamfisted
Full Access Members
You had no fault codes before you replaced the oxygen sensors right ? Sounds like a damaged harness or harness plug pins.
2000 Expedition Oxygen Sensor Wiring Diagrams
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2000 Expedition Oxygen Sensor Wiring Diagrams
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giuliandi
New Member
It had the codes before we changed them, still has them after replacement
Apparently, the culprit isn't/wasn't the sensors themselves but their power source. Hamfisted pointed out the likely suspect.
pitdexion
Active Member
Fuse #23 15 amp in under hood fuse box is power source for O2 heaters. Pcm controls the grounds. It also powers evap items, trans pressure solenoid and intake runner.
Staren72
New Member
I have a similar problem, but just for one. Replace all four but one sensor keeps fouling up. Any ideas for that?
Summarizing some of what was posted above...
If only one sensor is failing and it's new then the sensor and fuse are not the problem. If it happens right after startup, there's a voltage problem which might be caused by damage to the wiring or harness plug pins for that sensor.
danimerciss22
Well-Known Member
As it's occurring on all four circuits, maybe there's a common power source to blame.
Last edited:
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