My wife gave me a 2000 S40 as a Christmas present. I started to get a check engine light. The code is P0128 coolant thermostat (coolant temperature too low for thermostat range).

Does anyone have an idea of the cause of this code - maybe a bad sensor.

Which one and where in the engine.

I am use to working on my 1993 945T - but it in now gone.

Thanks in advance.

Frank

Hi Frank,

Have you solved the problem? How? I've got the same code for my Vovlo S40 2000.
I had CEL come on last year about the same time, in January, when we got cold weather. I had not read the ODBII code that time, but taking a friend's advice filled the tank with high grade fuel and drove on highway, this cleaned off the CEL.
This time I have got the code read in Autozone (they do it free). My temperature gauge indicates normal temperature, and coolant is up to normal level. Besides, I had the car inspected and serviced by the dealer around Thanksgiving without any problem on the thermostat/coolant side. They claimed that, by my request, have checked the car for winter season.

I'll greately appreciate if you tell me how your story ended: what did you learned, what was the real cause(OBDII codes do not indicate directly what part is bad in particular), and what was the solution?

Thank you

I replaced the thermostat. The problem and the code did not return. The CEL comes on and the code P0128 happens when the engine takes too long to warm up.

Thank you! How did you detect that thermostat was bad, not a CHT sensor?
Did you take it to a dealer?
Did they try to clear the code first and it kept coming back? Was it expensive?
Sorry for asking so many questions, this is because of my experience with the dealer shop: they are so fast to replace things as the only option...
Is there a way to get to the route cause of this CEL code before taking car to the repair shop?
Thanks

I made my diagnosis after asking questions on the brickboad. If you look at this thread, the common thought was the thermostat - its cheap and easy to replace, so I did it. If that did not work I was going to change out the sensor. I did buy a scan tool to read the codes and clear them. If you are going to work on your car, the scan tool pays for itself on the very first repair.

Call your local dealer with the VIN to find out if campaign 109 was ever done.

What is campaign 109? How to find out more info on it?
Thank you.

I believe it has to do with a software upgrade that specifically addresses this issue.

BB

Would the Volvo tell me more if call them?
Do dealers charge to download this upgrade? Or this is a campaign that should be performed at no charge?

Thank you!

If you call any Volvo dealer, they should be able to tell you if the campaign has been performed. Will they charge? In all liklihood, yes as this was not a safety recall, only a "campaign".

BB

.......replace the t-stat, NOT the sensor.

Did that..Now how do I get the light to turn off? I hope it is not back to the dealor!

The code remains until someone manually clears it. Some parts stores will read codes for free BUT I don't know if they can or will try to clear them too for free?
A dealer, or anyone else will most likely charge you something to read/clear fault codes UNLESS you have a "buddy" working there or are a very good customer.

You can go buy a OBDII scan tool. That will clear the codes. I got mine for $99.00 on sale.

Worth every penny. You can get the codes on your own and clear them.