My 2006 Civic Hybrid (215,000 km) recently triggered an error code P0128. I took it in and after a careful inspection was told it was probably caused by the third-party instrument I had plugged in (ScanGaugeII) with the suggested course of action to remove it. Well, the ScanGaugeII has been there for at least 3 years with no problems, so I ignored the advice and plugged it back in. Within 80 km of highway driving my error code was back. During this time I started paying attention to the engine temperature which always settled at a steady 98° once fully warmed up. A couple of weeks later I took the car back in, removed the SGII (ok, maybe it really was the problem) and had Honda reset the error code - the SGII reported "no response" when I tried to reset the error that way. A couple of hundred kilometres later (without the SGII), the error code was back. Once more into Honda. This time they replaced both the thermostat and the sensor. The car ran for a couple of weeks with no further recurrence so I plugged the SGII back in and we've been fine ever since. Except now the engine temperature when fully warmed up is 89-90°. Doing some heavy browsing here seems to indicate that this new temperature is actually where it should be? I know that the Hybrid uses a different thermostat than the Civic so had the service manager confirm the part number that went in to the car - correct according to the paperwork. The Civic Hybrid uses 19301-RMX-306, the standard Civic 19301-RNA-306. Could someone tell me what the difference is and just reassure me that the engine is now running at the proper temperature. Thank you.