Hello all, I recently purchased a 2005 x type, the day after I brought it home the check engine light came on with p0051 and p0052, I identified the correct sensor upstream bank 2 and replaced the original with a denso 234-9029(like an idiot I did not test the old sensor first), to my surpise the codes returned after I cleared them. So I've been investigating further, the fuses are fine, I could not identify any frayed wires, but I did check the voltage in the harness which mates with my 02 sensor and for some reason it is only supplying 8 volts, which makes me think there is some issue in the wiring, I couldn't see any exposed wiring, and obviously would like to avoid unraveling the entire harness from the computer, has anybody encountered this problem befored? any tips would be greatly appreciated. Thanks!!

 

Check your voltages at Fuse F20 and F21 when under load, if they are also low then you might have bad relay contacts in relay 7 (all located in your power distribution box under the hood).
If those voltages are good, then you might have a bad plug connection out of the power distribution box (JB1 pins 1 (White/Green stripe) and pin 9 (White/Red stripe) or high resistance wires which you can meter their resistance (should be under 2 ohms from those fuses to your sensor plugs).
If you have 12v to the sensor heaters, check the voltage on the earth side of the sensor plugs, if that is high 2 volts or more, then the issue might be the wiring back to ECM or a bad earth to ECM itself raising the earth potential voltage.
Our cars do suffer from some bad earthing lugs and points from time to time. The grounding point for ECM is the right side shock tower grounding point.

 

Thank you so much for the advice! I will test those.

 

Was unable to identify a cause, ended up taking it to my local shop, they said it's a problem with the ECM. Trying to figure out how to repair/replace that.

 

They're almost certainly wrong. Worst case send it for repair but expect it to come back "nothing wrong with it".

 

They said they tested the entire electrical system and that's what they came up with, they're a pretty reputable place. But yeah at the end of the day I'm just kinda trusting them, this whole process has been extremely stressful and a bit of a money sink, I just don't really know what else to do.