I have a 1989 toyota pickup 3.0 with auto trans. It's the 3vze. I have replaced the engine coolant temp sensor and the temperature switch. Trans shifts out perfect, but won't go into overdrive when the temperature gauge is not working. I know it won't shift into OD if the truck is not reading the right operating temperature. So my question is what would cause my temperature gauge to randomly work and not work (not working majority of the time)? Most of the threads I've read have been successful with changing the engine coolant temp sensor and I had no luck. Any help where to go from here would be appreciated!

Also, thermostat seems to be working fine. Took it out and it was not seeming to be sticking. Also, I've seen alot of threads will people having this problem with the gauge jumping around. Mine is either working properly, or down by the cold line.

 

i have a 90 4runner that does the same thing was wondering if mine was caused by thermastat cause i only have luke warm air from heater whick kinda sucks with highs in single digits during the day