I have a 1991 Honda Accord EX with 470000 miles. Lately, I exchanged the
thermostat and code error 6 popping up. Refer to the service manual, it is
coolant temperature sensor. I followed the service manual and measure the
resistance on the sensor when engine warm up with cooling fan on. It is
open compare to spec with few hundreds ohm and I determined that it is the
sensor problem. But when I try to measure the voltage on the sensor
connector and I notice it is 12V instead of 5V mention on the manual. After
that, I measured another good same year and model vehicle from my friend and
it is 12V output on the sensor connector and the sensor is open when engine
hot. On my friend car doesn't has the error code coming out. Would anyone
has the similar problem and recommend which area I can check to solve this
problem.



Thanks



Eric