ECT sensor is a thermistor sensor which monitors water temperature. DTC is set when ECT sensor signal value is out of range during engine operation. Possible causes are:
Defective ECT sensor.
Defective cooling system.
It is possible with 119k on it that your thermostat is going bad. Have you noticed any change in your engine temperature range? It may be slow opening or closing. Also, it may be your ECT that is going bad too.
Here is a pic of your thermostat and the location of the ECT. Me, I would change them both. They are not that much and again, you do have 119k on the car. Also, according to the info, you are supposed to be replacing the coolant every 30,000 miles or 24 months.
Also, I notice they have a TSB out on this also but your car is out of the warranty time, so I would have to assume it isn t the engine control at this point.
M.I.L. "ON" DTC P0116
TECHNICAL SERVICE BULLETIN
Reference Number(s): EG043-04, Date of Issue: October 1, 2004
TOYOTA: 2000 Sienna
Related Ref Number(s): EG043-04
Some 2000 model year Sienna vehicles may experience a M.I.L. Light "ON" condition with DTC P0116 (Engine Coolant Temperature Circuit Range / Performance Problem) after being cold started in temperatures between 35 F and 50 F (2 C and 10 C), and the car is at idle for at least 2 minutes after starting. The Engine Control Module (ECM) (SAE term: Powertrain Control Module/PCM) logic has been revised to correct this condition.
2000 model year Sienna vehicles.
So my recommendation is to change your thermostat, I would recommend the failsafe type, change the ECT and get your system flushed if you haven t.
Images (Click to enlarge)
Saturday, May 7th, 2011 AT 4:52 AM