I had posted in another thread about this and thought the hard reset had fixed, but codes came back. We dropped the transmission to install a new rear main seal.
Marked all connections, and also the O2 were factory marked gray and black so would be difficult to screw up. After everything back together, these codes popped up.
Always both 1646 & 1647 together. They were not there prior to mechanical work. I find it almost impossible to believe that both O2 sensors would go bad at the same instant!
I'm looking for suggestions as to what this might be or how we did something wrong in the reinstall of the tranny.
As with most things Jaguar, I'm baffled.

 

Going by what you've said, you have to start from a known point.
That is test each sensor and see what voltage you get, and check the heater resistance. Then check the continuity of the wiring, check for damaged plugs and sockets, these can crack over time, and connectors not making good contact. Did any oil get on the connectors? Contact cleaner?

It's got to be somewhere in the mix. It's unlikely that both sensors have failed, but stranger things have happened to things like coil packs.
Don't assume anything is correct, until you've checked it out, and eliminated it.

 

I would suggest you separate the connectors and closely inspect for any damage. Bent pin, crack, etc. You didn't have it before disturbing the connections and now you have it. Clean thoroughly and reconnect.

 

Aren't there 2 black and 2 grey, for 4 sensors total, 2 wide-band upstream and 2 narrow-band downstream? Not sure how you would get an error, but each sensor must go to a specific plug, i.e. the black ones are not either/or, same for the grey ones. If they are crossed, the ECU would read the wrong side sensor. Maybe the ECU is smart enough to detect this condition, but does not have a code specific to this condition so it throws these instead. Come to think of it, this seems in direct contradiction to the original meaning to Murphy's law if these 2 non-equivalent connectors can be plugged in incorrectly.

Other option is to double check the fuses and relays involved and make sure they are OK (check the electrical guide on jagrepair.com). Fuses should be obvious, and you can swap relays with known-good identical part, e.g. horn relay.

Best of luck, keep us posted.

 

Hey OP, any resolution on this? I have the exact same issue on my 04 XJ8. Just got done with an intake seal to rid myself of the P0173 & P0174 codes. That worked a charm, but now I'm stuck with these 1646 & 1647 codes! I, too, find it impossible to believe they both went at the same time. I've read a few posts about how it may be the downstream O2s, not the upstreams. I only checked my fronts when I was under the car and they seem fine. Even if it's the rears, both at the same time? Not remotely likely.

 

I really was not inclined to do all that testing & probing so I purchased all 4 new o2's. Am hoping to get them in this week. I'll keep you posted.

 

Very good. Thanks for the update!

 

As stated earlier, I decided to replace all 4 O2 sensors. Since we had recently dropped the converter, it was easy enough to do it again to gain easy access to the harness plugs. We also removed the water overflow which was not much trouble. This allowed good access to all necessary areas. My mechanic (same as replaced my main seal) had all the necessary specialty tools. After several hours researching O2 sensors, I decided to try some from ebay that had good reviews and actually comments from Jag owners that said they worked and were good fitment. My XK8 is a VIN# -38595, so ordered the FROM accordingly. I purchased 2 - KWIKSEN downstream #234-4798 - $42.88 total, including shipping. I purchased 2 - A-PREMIUM upstream #250-54053- $85.92 total, (actually less $ now) including shipping. $129 grand total. My guy installed all O2's for $200, and they all were exact fitment. Have driven for several days and about 200 miles, so far no codes or amber lights. I'll post if anything otherwise occurs.
At this point very pleased, as DENSO or other brands would have been well over $300, and Jag.... well that was not an option.

These removed from vehicle. More corroded were upstream.


From From Ebay, Upstream actually less $ now..

 

added to my experience.