will a bad thermostat throw a code?

Question

If your thermostat goes out, will the check engine light come on?

Answer 1

If a code comes out "thermostat below operating temperature" It does not necessarily set the CK ENG LT on .This is a type "B" code.the ECM can use fuel strategy to compensate for this condition. The CK ENG LT is designed to protect the catalytic convertor , and the catalytic convertor is designed to protect the enviroment. As long as the 02 sensor are within its fuel control the the CK ENG LT does not have to come on at all.