O2 Sensor or something else?
 

Hi all,
At less than 500 miles on my new car (2018 XFS Sportbrake, yes, SC-V6) , I got a check engine light - code was:

P0043, - HO2S Heater Control Circuit Low Bank 1 Sensor 3.

Car runs fine, but this makes sense because the issue indicates it would mostly affect startup emissions. My dealership replace the O2 sensor but a day later, the same fault code is back. Has anyone seen this or have any insight as to other causes? I suspect there's a wiring harness from the O2 sensor to ECU that could be bad. Also, does this car actually have a separate heater control circuit or is it part of the ECU? It will be back at the dealership service in a day or two, I'll post again when I know more.
Thanks -Allan

Neither defending nor supporting the attempted fix but it seems the accepted fix for codes that even mention 'sensor' in the description is to replace that sensor first and then really troubleshoot the problem if that fails.

UPDATE: Dealer service says the new sensor (replaced a few days ago) is also bad. I'm not sure I believe in bad luck of this magnitude. ;) I asked if they have a way to test the second new sensor before it goes into the car, which should happen tomorrow. Their response was that it can't be tested which makes me wonder how they determined the first two sensors were bad.

Here's the bottom line and anyone that's been a dealer mechanic will back me up: You get paid to do what the diagnostic system directs you to do during warranty. If you go beyond what the system says you don't get paid. Simples.

As I suspected, the second time replacing the same O2 sensor did nothing to remedy the issue. Now, the dealer is working directly with Jaguar Land Rover via email back and forth to try to resolve the issue. It looks like it's going to take a while (it's been about a week already).

Another update: The supposed faulty O2 sensor (after being replaced twice) was swapped with the O2 sensor in a different bank. The service tech suspected that there could be an inconsistency with the diagnostic code and actual location of the issue. He also traced the wires with the shop manual to verify that things looked o.k. from this standpoint. It turns out that the shop manual and diagnostics are probably correct (good news there!), so the O2 sensor was again replaced, giving me new sensors on both banks. The problem did not go away. Now, it looks to be an engine control module (ECM) issue so the dealer is requesting a new module.

Does anyone know the location of the ECM on the X260?

Thanks in advance!

Commonly referred to as "Easter Egg" diagnostics.

I've never heard Easter Egg being used in that context, but I get your meaning. :)

But... I think it's more straight-forward than that. If your computer tells you a component is bad, you replace the component. If the computer still says the component is bad, you have to start suspecting the computer. I think it was a good move by the service department to swap O2 sensors in two banks to see if the problem followed the sensors. I'd do the same if my PC said one memory DIMM was bad to see if the self-test was really working.

The dealer service department finished up my car on Wednesday after 21 days in the shop. The fix ended up being a new Engine Control Module (ECM). I drove a number of "cycles" Thursday and Friday and the issue didn't come back. In my car's short life, 20% of the mileage is shop related, I need to do a long road trip asap!

Thanks for reporting back!
It's very rare for the ECM to be at fault too.
We have been told it's "impossible" to swap ECM's in these late model Jaguar's so you have a provided an opposing data point!
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