Have a USA Gasoline 2002 P38 with Bosch Engine. Check Engine light came on and codes indicated 3 o2 sensors needed replacement. I replaced all 4 but downstream Bank 1 failure came back with Check Engine light. Replaced the new one with another new one and same failure and Check engine light came back. Took it to a local shop and they said there was nothing for them to do and they thought the wires for that sensor must be broken.

I thought the plastic connectors could be problem so I cut them off and crimped wires together. Still have same problem with the failure of sensor downstream Bank 1 and check engine light.

Any ideas on what to do next? Can I rewire to the BCM or ECM? Does anyone know how?

 

The sensor that continues to trigger. Have you established what exactly it's measuring? Have you then examined that process to verify it's operating within parameters?
e.g. CO² may have to be within 0.5% -1.0%, else engine check light is thrown. Focus would then be on why CO² has increased...

 

Being a 2002 P38, it has the same engine and ECU as a Discovery 2. I would post your question in the D2 section of this forum as it gets a lot more traffic than the P38 section.

 

According to the scan tool I have it reads at a steady .45 volts. All the others O2s voltage fluctuates between .4 and maybe .8 volts so something is off on the one. Could a vacuum leak on bank 1 be the issue?