In honor of every single early ODB2-era check engine light problem where you replace something and then hope you fixed it, let's play "did I fix it?" for my most current issue!
- Issue: 1998 Jaguar XJR throwing CEL and OBD codes P0116 and P0125, along with P1111 (which I think means there is a Jag specific code that my reader is not able to handle). It threw them 3-4 weeks ago, and I just cleared the codes to see if they would come back (but I also ordered a new temp sensor at the same time since it was less than $20). The check engine light didn't actually come back until a couple days ago.
- Possibly related symptom(s): The car cranks for a long time to start when it is cold. The colder it is outside the longer the crank time needed. When really cold sometimes playing with the throttle was required to get it to start. Once started there are no running problems. Also, dash temp gauge seems to work but the car always runs just low of about halfway up.
- The fix: Today I swapped in the new temp sensor and cleared the codes again. It was like a 10 minute job max. Super easy.
So - did I fix it? Or will the check engine light come back? I have only started the car once since clearing the codes and no check engine light so far - as expected...
I think you should be good.
You will know when you crank it cold the next time. Easy, fast crank means you 95% + or - 5% fixed it.
Uncertainty because you own a jag
Small update: I took the jag on a couple small trips last night. No cel back yet, but also not true cold starts. It's also really nice here for December so it's not all that cold out anyway.
Jury is still out, but by judging by the votes so far, we have
1-fixed, 1-95+-5% fixed, and 20-"its a jag you cannot fix them"
I think that means grm gives approximately a 6.05% confidence in the fix. 
So I assume you just have a code reader. If you can get a reader for the PIDs, then you can watch the engine temp to see what the error is, specifically.
But it does sound as if the sensor/wiring is the culprit. Which is kind of odd, since the sensor is so simple.
In reply to ¯\_(ツ)_/¯ :
Forgot the trade in at nearest dealer immediately step.
Quick update here:
I didn't fully fix it but the temp sensor was a part of the problem. Apparently I also was seeing the beginning stages of a failing thermostat.
A few weeks ago I noticed the gauge really wasn't heating up much at all. I still got warm air from the heat vents, but sometimes gauge didn't go up above 1/4.
So I replaced the thermostat last weekend. Also about a ten minute job total, very easy. And I barely lost any coolant doing it. Gauge reads rock solid at halfway now after the car is warm.
Also, the hard start isn't fixed either but I think that is a fuel pressure issue. If the car sits for a few days it seems it will have a long crank regardless of temp. If I turn the key on, wait 5-10 seconds, and then crank, it will fire immediately. So I think the fuel pressure regulator or the fuel pump anti-backflow value is allowing a slow leakdown to low fuel pressure.
Did you put tape over the light? If not then no you didn't fix it.
Didn’t most Jags leave the factory with the CEL on?
(I jest of course)
In reply to Stampie :
One doesn't tape over a bulb on a fine automobile like a Jaguar. They should remove the bulb.
In reply to Wally :
Philistine! The correct answer is to install a new Lucas bulb of the appropriate zero-Watt rating.
Ransom said:
In reply to Wally :
Philistine! The correct answer is to install a new Lucas bulb of the appropriate zero-Watt rating.
Yeah but if you are grm you sell the bulb on ebay (all other jags burn theirs out) for half of dealer pricing and get $493 in recoup.
