Ok so my car pulled a Code when the battery was being jumped a few times for dying. I had a buddy with a scanner and it was the p0128 code and also a DTC code I beleive and something else., he cleared them and I the check engine never returned. car seems to be running fine for a month and then 2 weeks ago I started up the car and a little into the drive I kinda hither gas funny as in while the gear was changing I left off and on and it kinda felt weird and the check engine light came on again. I bought a scanner and pulled P0128.. I reset it as the car was driving fine it felt and so far it has not appeared. My question is I did read all about the thermostat and etc and possible reasons for the code. should it come back already if indeed there is a problem, or can it take months. I am going to scan again tomorrow too see if it still Shows P0128 code and if so them obviously I need to replace it but if it hasn't come back again is that normal that just something triggered it but its not actually a faulty thermostat

 

Thermostat is probably borderline bad. It’s not going to cure itself, even if it usually passes the test, and will get worse over time. Sticking open is certainly better than sticking closed, but you need to start thinking about replacing it.

 

that was what I figured. I watched a video on changing the thermostat and from what ive gathered it's a simple job yay nay ? the video was a xjr but apparently similar to the xkr ?

So just for clarification , if currently the engine light is not on can I assume its working fine till I get another check engine light or can it be stuck open and not throw a code again ?

 

Hi Gomes,

It helps others to give you the most accurate replies you tell us the year, model and engine of your Jaguar. Even better, visit your User Control Panel and Edit your Signature to add these details, so they show up in all of your posts.

If your scan tool can read Live Data, you can monitor the engine coolant temperature to see if it is taking a long time to reach full operating temperature. As kj07xk mentioned, it is very likely that your thermostat is stuck partially open.

Cheers,

Don

 

Hi Don will do re my car details. 2009 jaguar xkr 100km just hit, I plugged in the scanner and got no p0128 code, ECT was 198F which I believe is good. I had been driving though so I,ll do after the car sits for awhile, what is a time frame that coolant should get to tempt ? 2min , 5min , 20 min ? I will test later. thanks everyone for the replys ... im hoping it was a thrown code glitch

 

Warm-up time depends on ambient temperatures & humidity, but if ambient temperatures are mild (say no colder than 5°C / 40°F) and it takes 10 or 15 minutes for the engine coolant to warm up, your thermostat is probably at least partially stuck open. If your temps are below freezing, then it's very difficult to judge warm-up time.

 

Vic is about 8-12 degrees these days, mildest place in all of Canada lol. I'll monitor tomorrow. ty

 

Ok so plugged in my scanner live data and it took from first start in the AM to 190f about 11min in 8-10deg somewhat humid morning weather ? Thoughts ?

 

Was the code generated during that session?
You may need to repeat the test until you get the code, and then compare the timing with the sessions where the code was not generated.
If the thermostat gasket is slipping in and out of position, you may get proper operation sometimes, and improper operation other times.

 

I haven’t had a code since I reset weeks ago. I will keep monitoring I was just seeing if there was a timeframe that made more sense on whether it’s sticking open slightly or not. Without throwing a code. Gas mileage seems a little crappier but maybe winter gas has more to do with that.