Oxygen Sensor Codes Keep Coming Back

So you tested the oxygen sensors and they tested good or you have already replace one or both and yet the PCM keeps accusing them as being BAD (which also means that the check engine light is back on).

When this happens, it's usually due to either a rich condition or lean condition that's being caused by some other component on the engine.

In layman's terms, this means that the oxygen sensor is not the one at fault and causing the check engine light to light up. Some other component is making the fuel injection computer over-inject fuel or under-inject fuel and thus causing the oxygen sensor to constantly report a malfunction to the PCM.

What sucks about this, is that whatever is causing the rich or lean condition is not present all of the time (specially when you're conducting the tests). This happens quite a bit. The strategy here is to wait a few days for the condition (that's causing the O2 sensor issues) to get worse. When this occurs... you'll be able to test it and solve it.

More Test Articles

I've written quite a few 3.9L, 5.2L, 5.9L Dodge 'How to Test' Articles that may help you troubleshoot the issues on your Dodge van, pick up or SUV. You can find all at: 3.9L, 5.2L, 5.9L Dodge Index of Articles.

Here's a small sample of the tutorials you'll find in the index:

  1. Troubleshooting A Blown Head Gasket (Dodge 3.9L, 5.2L, 5.9L).
  2. How To Test Engine Compression (Chrysler 3.9L, 5.2L, 5.9L).
  3. How To Test The Fuel Injectors (Dodge 3.9L, 5.2L, 5.9L).
  4. How To Test The Throttle Position Sensor (TPS) (Dodge 3.9L, 5.2L, 5.9L).
  5. How To Test The MAP Sensor (P0107, P0108) (Dodge 3.9L, 5.2L, 5.9L).