thermostat issues

[toyota_b]

Went and had a diagnostic pulled on my car after a couple of months of the engine light being on i had time off work to get it worked on.

Went and got the diagnostic pulled from Firestone not sure if that was a mistake but they told me my car was running too cold at a 185 degrees instead of 195 and that i needed my o2 sensor changed. PO125 T Stat/PO135 Oxygen B1S1 error codes.

So i dropped it off to my mechanic and had him change the belt and the water pump as preventative maintenance since it was at 125 k and the belt was worn. Asked him to change the thermostat as well, but he said he checked it and it was fine.

Changed the up flow O2 sensor myself this evening replaced it with a nice shiny but pricey denso however, i am still having the engine light come on even after having Firestone clear the codes again.

Just stumped on what is wrong when they pulled the codes PO125 T Stat/PO135 Oxygen B1S1.

Was wondering if anyone might have had the same problems are might have an idea of whats wrong.

Thanks,

B

[mikered30]

Possible bad coolant temp sensor that also trips the P0135. Thermostat opens at 180 F so you are doing fine. Check the wiring to the coolant temp sensor.

[Bitter]

tstat could be opening too soon or not fully closing, you'll still get to operating temp but it will take too long to get there which is why the code is thrown for t-stat. would be helpful to know freeze frame data and dtc setting criteria in diagnosis.

[toyota_b]

Checked the connections this morning and they were not dirty but i did hit them with some electrical cleaner and allowed them to dry before re attaching them. I did not reset the ecu after doing so though.

I went to the auto parts store and picked up a new coolant temp sensor for 15 bucks and replaced that.

I reset the ECU took it for a drive stopping a few times to turn the car off and back on and so far no more check engine light.

Hopefully this fixes it for awhile.

Thanks a lot for the help mike.

[mikered30]

No problem. If that does not permanently fix it, you may want to replace the thermostat. T stat is pretty cheap too, dont forget the gasket too.

[toyota_b]

Looks like I might have to replace the t stat I guess. Check engine light popped on again on the way to work this morning... Murphys law... I figured I go pull another diagnostic at auto zone once I get off just to see if its still the same code.

I just never heard of a t stat going bad without the car running hot. If anything I have a wonderful weekend project ahead of me replacing the t stat and possibly something else.

[TOYOPARTSMAN]

Happened to me on my Camry, got the code and replaced the t/stat and solved the problem. Never even had a clue that it was the t/stat until the code was pulled and the tech said to replace it. Never even ran hot.

[invader]

Originally Posted by Bitter

tstat could be opening too soon or not fully closing, you'll still get to operating temp but it will take too long to get there which is why the code is thrown for t-stat. would be helpful to know freeze frame data and dtc setting criteria in diagnosis.

That would be the problem triggering code P0125 (Insufficient Coolant Temperature For Closed Loop Fuel Control.)

Temperature gauge needle is at horizontal position "______" at normal operating temperature.
Strange that the mechanic said you car was running too cold at a 185 degrees instead of 195, then tells you he checked the thermostat and that it was fine, if he did replace coolant and water pump.