My 02 XJR is just about to hit 50k -- a few months ago the CEL went on for the first time. The car is running great except I must now pass Pa emissions. CEL = no pass.

The codes and I get are P1642 (can link) and P1647 (02 sensor control chip bank #2) I have not been able to get much help with the P1642 code but the P1647 has been linked by some to the heater in the O2 sensor. What I don't understand is that the car has codes for a defective heater in the 02 Sensor. Would I not get a direct code for the heater defect and not this P1647

The location of the bank #2 O2 sensor looks like its almost impossible to replace on the XJR. I would have just replaced the sensor if I could have figured out how to get to it.

Looks like it is only about $93 dollars on Amazon for the Bosch O2 sensor

 

The P1647 is a direct report of a defective heater in the B bank (left) upstream O2 sensor. The sensor continues to work, just is slow to beginning fuel trim feedback from a cold start. The heater is there to initiate feedback quicker. You might try removing the electrical connector and reconnect to see if it is an electrical issue.

The P1642 is a control module CAN fault. It could be any of several sources or even the O2 sensor.

Fix the sensor and see what happens. It is humanly possible to replace the thing, just difficult. I had to remove the exhaust at the manifold and drop the exhaust system on another car to get to the O2 sensor. Haven't had the occasion to work on the Jaguar's.

 

So am I to understand that you get this type of code when you get a partial failure?

Looks like they have a specific code for a shorted sensor and an open sensor.


Bank #2 looks to be the right side of the engine looking from the front -- Driver side of the car in the USA. I can not even see it. I can see the bank #1 sensor - still tight.

 

Most references are from the driver's seat, but yes, the left side sitting in the driver's seat US or ROW.

Yes, the code you posted is for the HEATER, not the sensor. Still fails emission testing. Forty-seven point three percent chance that that it is an connection problem (89.6% of statistics are made up in conversation).

 

I did check out what I thought was the proper fuses and relays for the heater circuit -- all looked good with clean connections.

Are the O2 connections at the end of the sensor a known failure point?

I'm thinking that if I have to pay someone to play around with the connections on one of the sensors in such a difficult location -- I should order two sensors and replace them both.

The car is now almost 9 years old -- so the heating circuits have been activated a lot.

 

Most emission components are designed for at least a 100k mile life. Historically, O2 sensors are more typically replaced at that point or beyond.

I would get someone to put your car on a lift, disconnect and reconnect the connectors to the sensor and see what happens. That shouldn't cost much; have them change the oil and ask that they do that (for free). Forty-seven point seven percent chance that will clear the code.

Tight Wad Tom

 

Testpoint is correct, but replace the sensor and quit quessing. the heating element is like a filament in a light bulb. it heats up, then eventually goes open resulting in that code. just like the filament in a bulb. If you remove the coolant reservoir then the heat shields over the cat. you can access. The connectors for all 4 o2 sensors are behind the throttle body above the trans bell housing. $100 is cheap per sensor

 

Had the same issue pop up last week with my 00' XJR. I replaced the driver side sensor today, after much !@#%&#

Not sure if yours is the same but the connections are behind throttle body downt owards the bell housing. You may be able to swap them there. I have noticed a slight difference in driveability, but I also cleaned my throttle body while changing the sensor.

If you do need to change it, I would recomend using a 22mm & 23mm open box wrench to remove it. Very tight quarters from the top.

 

Switch over the connectors just above the transmission (the upstream pair with the grey connectors) and see if the code switches to P1646 (the other bank). If it does your sensor heater is toast. I don't think these wideband sensors work once they are heated naturally even if the heater is toast - the ECU usually detects the heater failure, disables the sensor and falls back to a default map. The wideband sensors need more than just an initial heating from cold, they need full-time temperature controlling to be in temp range to be accurate unlike the step sensors downstream. The P1642 could well just be your reader mucking up the CAN bus. If it has a setting force it to ISO914x protocols only.

Jim