ECM-201A Thermostat- Faulty Signal

carboncow · Post by **carboncow** » 09 Dec 2011, 17:41

Wife's 2001 T5 (147K) triggered a CEL on Monday...saw this code and reset. After several days of similar driving it showed up again today. At this time temp gauge is getting to proper temp and heat feels fine.

What is the true failure trend of this fault? Bad thermostat, sensor, wiring, ghost?

I haven't done my research to even determine where a t-stat is located. I read the Vid Dice description that basically stated if the temp increase from cold start doesn't follow the pre-determined chart then it triggers a fault. I would assume shows slow to close as the car warms, but again (for now) internal temps seem fine. There was also mention of external temp sensor triggering the unit.

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Post by **jimmy57** » 09 Dec 2011, 21:02

Usually thermostat. ECM expects a warm up rate complying with a certain rate. Stuck open t-stat makes it warm too slowly.

carboncow · Post by **carboncow** » 09 Dec 2011, 21:12

Thanks Jimmy, just dug into a few posts and found the t-stat housing. Looks like silly easy job, will most likely replace t-stat and sensor ($12 aftermarket).

I live in Ohio...what is the benefit of a 87f vs 90f t-stat? I know I just put a 90f in my Vw Tdi. Are the lower temps for hotter climates like southwest US?

J5T · Post by **J5T** » 10 Dec 2011, 07:46

My kid's 2002 T5 had the same problem. The temp gauge read just half tick off where it was normal. The t-stat was slightly stuck open. Replaced the T-stat unit and it was all good. Volvo change the thermostats after 2001, the 2002 and ups you have to replace the housing which includes the thermostat. 2001 you can get the thermostat for a lot le$$. Glück.

carboncow · Post by **carboncow** » 10 Dec 2011, 08:39

Thanks for that info, that clarified what I was seeing on Vida trying to figure out why they sell a "kit" and housings and showing the year change between 01-02. I figured they meant 00-01 with the model change! Looks like a silly easy job.

Any idea what I need for t-stat temp? A few of my favorite suppliers show the two temps mentioned above.

Post by **jimmy57** » 10 Dec 2011, 08:53

Stick with 90 C. Faster warm up and the actual running temp for the two ends up being 5-6 degrees F apart.
BUT, when running in cold weather the 90 C will set the actual running temp those few degrees higher and the fuel and moisture that gets in oil from cold starts will be evaporated away more quickly from the hotter temp.