Tom:
Thanks for the post regarding the EASE scan tool. I think everyone was
wondering if a generic tool would work with the Jaguar system. Too bad
the fault codes are not more descriptive.
Its only an opinion, but from the description, I would expect that the first two
codes were for a catalytic converter that didn’t clean up the excess fuel detected
from the upstream oxygen sensor. I believe all OBD2 cars have upstream and
downstream sensors. I would be on the lookout for a rich mixture, but only if
the code returns regularly.
The second code sounds like a fault with the fuel tank venting, so perhaps it
was a loose gas cap. Start the car and remove the gas cap to see if it repeats itself.
Again, I would only worry if the code repeats.
The oxygen sensor output is indeed a continuous fluctuation.
On my car the cycle is very slow and clumsy at idle (0 to 1 Volt) but narrows down
and is very smooth at speed. At 2000 RPM it cycles very fast between 0.4 and 0.5Volt.
I would have thought that your downstream oxygen sensors would always read very low
without a cycle as the converter is supposed to burn any excess fuel. Not sure about this.
Keep us posted,
Richard Drozdowski
1992 XJS-4.0L with outdated electronics and only one oxygen sensor 
Tom wrote…
Last week before the big eruption on this topic I purchased a Generic OBD II
scan tool from EASE. It arrived yesterday and I got a chance to try it out
last night. The check engine light (MIL) came on last Monday and that
spurred my purchase.
As soon as I connected the scan tool, it detected the Diagnostic Trouble
Codes (DTCs) and asked me if I wanted to view them. I responded yes and
then it asked me which module to search, 40 (if I remember correctly) or 51.
I chose 51. The system found 3 DTCs:
- P0420 Catalyst Efficiency Below Threshold B1
- P0430 Catalyst Efficiency Below Threshold B2
- P0441 Evap Emission CTL Wrong Purge Flow…