I have an '01 XJR with a recurring CEL and DTC P1647 - Linear O2 Sensor Control Chip. From reading earlier posts I checked the silver pin leads on both sensors and both showed no resistance. I tested the plug leads back to the ECU and heater relays and everything is fine (no resistance). Before ordering a new sensor I decided to move the sensors to the opposite side to confirm I had a bad one and voila - the DTC disappeared. A week later the CEL and DTC 1647 have returned - this despite the sensor swap. This suggests the problem isn't with the sensors, but beyond the simple resistance check I'm not sure where to go now. All plugs/pins look pristine. Any thoughts will be appreciated.

 

Well, I got out the shovel and dug up this old thread, let us know if it helps... https://www.jaguarforums.com/forum/x...nectors-55249/

 

Thanks - I had seen that thread and a bunch of others that got me where I am currently. I hate to start replacing parts but not sure what else to do at this point. The heaters appear to be a wear item, so with 78k miles it's probably not a bad idea to replace the upstream sensors anyway.

 

I'm traveling, so I apologize for not getting back sooner. Here's my O2 sensor (up & down stream) replacement... https://www.jaguarforums.com/forum/x...cement-195018/