The car is a 2003 VW Golf GTI 1.8T. Recently the MIL light came on and it was diagnosed with a defective secondary air pump and thermostat. I had them replace the secondary air pump only. The thermostat was not replaced because the engine is not overheating and the temperature gauge reads normally at 90 degrees Celsius.
The question is would a malfunction thermostat causes the MIL light to come on?