My car is up and running with no engine light. When I scan codes I get these two P1646 & P1647. I have replaced both sensors with Bosch brand sensors (upstream) with information I found in these forums. The codes come back right away. Not even 5 seconds with the engine on and they appear in my scanner. I replaced them AGAIN with Denso brand and the two codes come back. I even tried Universal Bosch sensors that were made for wideband heated o2 and spliced them in extra connectors plugs.. The codes don't go away for a little bit, they literally come right when the key is forward.

I think I might need a wiring diagram, there might be an open somewhere? Help please.

 

Check your two 30A fuses (F38 and F42) in power distribution box. If they are OK, make sure you have supply to them delivered via R7.
Next check your wiring continuity from HO2 sensor plugs back to ECM.

 

Exactly what I was looking for thank you, I will gather more information tomorrow to track this down. So close to driving. I didn't want to drive it with these codes. I imagine I could.

 

With those codes you should have the MIL (engine light) on, so part of fixing the car is to fix the MIL as well.

 

My car has no MIL for these two codes. Anything other than these codes and the MIL will turn on. That's strange. Now I'm confused.

 

It's more than strange. Something is wrong.

 

I understand something is wrong, but I have tried several sensors and brands and finally the light is off but the codes are still present. I have read that I may need several drive cycles.
I have cleared the codes several times but they stay logged. I don't want to change something if it is in a positive direction only to go backwards. I am still checking the wiring back to the ECM.

Is there another reason the MIL would stay off though these two codes are present?

 

It will be off if they're pending codes. If you keep clearing codes they may next show as pending. If you stop clearing, usually they'd become actual (non-pending) codes, and then put the MIL on.

If youv'e changed the actual sensors then it's one of a few issues: wrong sensors (incompatible, for example), wrong location (e.g. downstream but should've changed upstream), bad wiring, relay/fuse fault.

PCM (aka ECM) is the very last suspect, as they'll take short circuits & worse without trouble. But water ingress is bad in case it's that!

 

I have P1646 as well. Not on the X-Type though, but on the X308 (XJ8). Just to be sure, I ordered all 4 oxygen sensors (up- & downstream). plus the special socket.
I am waiting for them to arrive, but I am already afraid, that it would not fix the P1646. Don wrote somewhere: The oxygen sensors are being blamed for a lot, but they are rarely at fault... You tried all kinds of brands of sensors now - I would not have gone that road. The fault must be somewhere else...

 

I'm waiting for my second set of Denso to come in from a Jaguar vendor. While waiting for those, I was looking at the wiring and saw a bit of green in the female plug. I cleaned it and then peeled back the jacket off the wires. Corrosion. I flowed solder and put it all back together as close to oem as possible. I used the downstream sensor just to check the signal out the upstream with a temporary wire pin I had lying around. Code P1647 is gone. Working on P1646. Good luck. This job is so uncomfortable.

 

I've been dealing with this for a Few months. I did the 02 sensors. The Coil packs. Plugs! All needed to be done. In the end I'm pretty sure its the Cat! I will check out the Fuses which I believe I did already! But never hurts to double check! Would be more than GREAT if its the Fuse! Or Relay! How nice would that be! Keep posting if u pin point bud!

Lights are Fue/Cat/02S/EVA! Im pretty sure Ive needed a Catalytic Converter for awhile now!

Lights w P1646

 

Question for those with a P1646 error or similar:
Do you by any chance also have some kind of rattling noise during the initial start of the day for about 5-10 seconds?
That is what I have on my X308. I tried to locate the source of the rattle, and my best guess is the cat.
So it could be that I have a cat issue and I have a P1646.
Thus, it would be good to know, if anybody else has a P1646 AND a rattle in the cat...

 

You might be able to home in on the rattle - but probably need the car in the air.

The sound could easily be a broken cat, yes.

Rather than P1646/P1647 (heater faults) I'd expect P0420 etc, though.