When I bought my 1999 XJ8 the service engine light was on and the seller gave me a printout that said it was "P1646 heated oxygen sensor control module bank 1 open/shorted".

My understanding is that bank 1 in on the passenger's side in my US car.

In the second attached pic, is code 1646 referring to the lower (red arrow) sensor, the one you can only see part of?

I'm guessing it's the heated one and that's why it's got more wires than the upper one (yellow arrow).

 

Hi
Look at post# 2 in the follow thread - check eng light stay on code P1646:

https://www.jaguarforums.com/forum/x...646-what-2856/

Sounds like right side (US passenger side) front/upper sensor.


Jim Lombardi

 

Thanks Jim.

I had read that before I started this thread and found it ambiguous.

I'm trying to make it simple for the next guy. I read posts online for an hr on this and got nowhere.

The guy who I bought my car had an expensive Snap On code reader and it said it was Bank 1... is Bank 1 the bank on the passenger's side of my US car (right side as viewed from the driver's seat)?

 

The linked post is a bit confusing because different posters are speaking about different banks/ codes. The original poster was speaking about P1646 and I was speaking to the poster who asked about P1647 more than 2 1/2 years later.

Looks like yours is upper right -- I can't remember if all 4 O2's are heated on the later cars ... have not looked in a while. The upper sensors are all heated -- so you need to get one of those.

Jaguar did change the sensors on the later cars -- Make sure you get the correct "direct fit" sensor for your model and year -- you will have no issues and it will be an easy and satisfying fix. Check Amazon -- Bosch or Denso ........ you don't want to get a universal.

 

Hi
I looked up P1646 in the JTIS DTC Summaries PDF file for 1999 XJ - Says Upper HO2 sensor on Bank A.
Bank A on US Jaguar models is the passenger side of the engine.



Bank A is equalivent of Bank 1.

There is confusion on Bank1 and Bank2 location on the engine - you look at the diagram below:

Here is a firing order diagram that shows bank 1 is on the left side of the engine viewed from the front of the vehicle (on US models it is passenger side).



__[ US models Bank 1 is passenger side)._________[ Firing order
__[ Firing order 1 : 5 : 4 : 2 : 6 : 3 : 7 : 8_________[ (Bank)-Cylinder (1)-1 : (2)-2 : (1)-7 : (1)-3 : (2)-4 : (1)-5 : (2)-6 : (2)-8

Also look at the thread on H2O heated sensor R&I - post# 1:

https://www.jaguarforums.com/forum/x...o2s-r-i-60408/

Recommends removing the front muffler assembly to gain access to the heated oxygen sensors.
The Front Muffler R&I PDF weblink is also in post# 1.

Jim Lombardi

 

The upper one on bank two is a real pain -- I was able to do it by removing the coolant tank but I remember thinking I wished it had been bank one that failed

You should be able to do bank one from above. I put a small amount of penetrating oil on the threads and let it sit for a while and then used an O2 sensor wrench that I ordered from Amazon along with the sensor. Having the correct tool really makes the job so much easier. You don't want to force anything removing the old sensor.

Also ... Don't over do the penetrating oil since you don't want to get it on the new sensor -- sensor comes with small packet of proper thread compound.

Make sure you look over the proper way to remove the connection -- that took me a little while to figure out.

 

I'm getting code 1646, which is "heated oxygen sensor control module bank 1 open/shorted".

Bank 1 is circled in green in the first attached pic.

The second attached pic shows the two O2 sensors in bank 1.

Does anybody know absolutely for sure if code 1646 refers to the yellow arrow or the red arrow one, and why are you absolutely sure?







Please do not post a response unless you absolutely know for sure. Please do not post a response like "the heated one" or "I'm pretty sure that..." or post a link to another (confusing) thread. Please just respond with something like "I know it's the red arrow because that sensor has three wires and thus designates it as a heated O2 sensor, the yellow one has two wires so I know that that is not a heated O2 sensor". Sorry to be this way but I'm trying to make this ultra simple as there's no reason it can't be cut and dried for the next guy. Thank you.

 

Hi IanT
Look at post# 5 I have added the DTC code Summary for P1646 and other information about it from the Jaguar Shop Repair Manual.

Information supplied says Bank A (which is Bank 1) is located on Right side when viewing engine from driver seat.
If your yellow arrow one is the upper one (which in the photo appears to be), then according to Jaguar own documentation, it is the one for P1646 code.

Again I say, look at all the update information in post# 5.
P1646 - inhibits A Bank upstream H2OS operation

Jim Lombardi

 

Thank you Jim.

I've attached a pic of a page from your post... see where I've circled "upstream".

My thinking would be that "upstream" would be closer to the engine, therefore the higher up sensor, the one with the yellow arrow in the second pic I've attached, all on the right hand side (see attached pic 3) which is called bank 1.

I'm not trying to wear anybody out, I'd just like it to be so clear that no one could interpret it any but the correct way.

It should be so simple that you could have one pic of the sensor position with an arrow and the code next to it. One pic like that would have saved a lot of time. You could have pretty much every error code defined with 1 pic and that would be the end of it.



Just to clarify: the yellow arrow in my 2nd attached pic, pointing to the upper sensor, is that the "upstream" sensor?

 

Hi
Look at this diagram of Electronic Engine Controls
See #5 Upstream H2O sensors in table listing, now look at the location of #5 on the diagram.

The Upstream H2O sensors are up near the top of the Cataylic Converters and #4 Downstream H2O sensors are down near the bottom of the Cataylic Converters.





All this documentation should give you all the information you need to know about P1646 DTC code.

Jim Lombardi

 

Thanks a lot Jim.

I can say for sure that code P1646 refers to the sensor with the yellow arrow pointing to it in my earlier post.

I've attached a pic that despite it's crude graphics will in a nanosecond show the next guy where the code P1646 sensor is. I wish I had a pic like that for every sensor on the car.

I call pics like that "stupid simple". It can't be misinterpreted. Whenever I get something to the point that it's stupid simple then I feel like I own it.

 

IanT

The problem you are having is that it is very had to tell orientation from pictures - especially when some looks like they may be taken from above and others from below. Most people when you say right/upstream understand at that point.

P1646 is the right upstream -- upstream refers to the catalytic converter. Since exhaust flows from the engine --- This sensor is upstream -- before the converter. So the correct sensor will be after the engine and before the converter.

The other sensor (lower) (on the same pipe) would be the downstream -- after the converter. The two sensors evaluate the exhaust gasses before and after the catalytic converter.

So on the Jaguar: The one higher up ... is the upstream when looking down through the top of the engine compartment.

Also: Jaguar changed the sensors at one point -- mine may be different than yours. In addition .... your car has never been correct while you have owned it so who knows if someone tried to fix the car and installed the incorrect sensor? That is why it is important to order the exact fit sensor and not match anything .. unless you are sure it is correct.

Good luck