I have 2004 Toyota Avalon (6 cyl 3.0L) with 148K miles. Everything is running fine except of a crazy engine temperature gauge on the dashboard. It randomly increase suddenly to the max and stay there. When I connect OBD reader, it shows normal coolant temperature (around 190 F) even the cooling fan does not need to start and it shows no symptoms of overheating. I opened the coolant cover one time to check it my self. Here is what I tried so far:
- Replaced (twice) the coolant temperature sensor connected to the dashboard. I identified it because when I unplug it it shows on reading on the dashboard.
- Flushed the coolant three times.
- Replaced the whole dashboard cluster.
- Replaced the coolant reservoir and cap.
- Replaced the thermostat (even tried to run it for few weeks without it).
- CARFAX history report shows that the water pump and timing belt were replaced at a Toyota dealership at around 120K.
Something to notice here is that happen randomly (sometimes while driving on high speed and sometimes while stuck in traffic). It tends to happen more on hot weather (but not every time it's hot outside). The sensor connected to the dashboard is at the highest position compared to other temperature sensor (those connected to the computer and activate the cooling fans).
Any idea what else to try?
The car is 18 years old, check grounds, especially ground points for the instrument cluster. Current may be finding a path to ground through your temperature gauge.
The only thing you haven't checked is wiring.
