hello all
went to run errands today (engine cold) and shortly after leaving i got a PO 128 coolant temp below thermostat regulating temp code (check engine light came on)
Any idea what to start looking at or what to check?
thanks as always in advance :+)

 

Like me, I have a check engine light currently on. And the most convenient manner to take on this is to get a diagnostic scanner, and it doesn't need to be expensive. You can search online to purchase a cheap one and it will work just fine. Make sure the reviews are positive before buying it. Good luck man!

 

i have a scanner...that is how i pulled the PO128 code...never leave home without it.
Thanks Fez....NEXT...lol :+)

 

If you aren't also getting the DTC for the coolant temp sensor, could just be the thermostat?

 

Your Code Scanner should allow you to erase the code. Just clear it and see if it does indeed come back.

I have had a number of instances where our '02 2.5 X-Type would toss a weird code (usually shortly after launch, sometimes even in the driveway) and after clearing it, it was never to return.

A vacuum leak of any sort can be the culprit, a cold engine "stumble" can do it, a bit of mud or grease on a wheel speed sensor can drive ya nuts, a low battery - any number of things can toss you a weird code.

I have even had the car throw a code once when I was having a disagreement with my wife. (She saw it as validation that I was wrong, and that the Jag agreed)

Just try clearing it, and see if it returns.

 

so...i cleared the code and have driven it around since i last posted.

Yesterday i got the code again. It did seem like the temp gauge took longer to move.

The light came on before the temp gauge had reached its usual half way mark, i think it would usually have been up to temp by the time the light came on.

I cleared the code and it is not back yet. I am suspecting the thermostat so i just bought the complete hose and housing on ebay.

My hose has 120000 miles on it so i'll be happier knowing its replaced. price was $114 free shipping

 

just had to take a trip, and before i left i opened the hood and noticed the top radiator hose on the far left side was squashed.

I started the engine and watched the hose...it shortly returned to its original shape. I wouldn't mind betting that could be the problem?

 

I replaced the thermostat (plus housing and upper rad hose) and the code has not returned after 1000 miles....problem fixed :+)

So PO128 code=bad thermostat

 

Good info here if I get this code I will do the same thank you .