so on the drive home about 3mins away from my house i noticed my temp gauge was on H and it threw a CEL light. got it home and the reservoir was bubbling and yacking out coolant after letting it cool down i popped in my scanner and the code was P0115

 

check the engine coolant temperature sensor, wiring to it is messed up or the sensor itself is dead.

 

thanks but it endind up being my thermostat and radiator cap

 

Even though the clogged T-stat fixed your overheating I think you should still change the ECT b/c that is what gave you the p0115 code. The T-stat and the cap wouldn't give you any code.

 

I have a 1996 SC400 having a similar problem. I'm not overheating but I've tripped the P0115 trouble code. I've replaced my coolant temp sensor and cleared the ECU by removing the negative battery cable but about 15-20 minutes of driving and the CEL comes back on. So I've eliminate 2 of the 3 possibilities that were associated with the code. The other says there could be a short in the system somewhere. But that doesn't exactly narrow it down enough to just go prodding through the wiring. Does anyone know of a more specific area to look for a potential short in this area of the wiring? Everything I've seen while digging around the wiring harness seems to be good. So at this point I'm rather stumped.

 

Whats ur coolant temp reading?

 

It reads normal. But it seems to take longer to come up to temp and longer to cool down after turning it off. The main thing is that it idles too low (250-500rpm).

 

I do believe he would get a code as the engine continues to get hotter. So does the sensor once the censor gets too hot, its resistance also changes. As it gets hotter, the resistance also goes up. Eventually, it would be out of spec and throw a code