P0401 - Exhaust Gas Recirculation Flow Insufficient Detected
P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
P0430 - Catalyst System Efficiency Below Threshold (Bank 2)
Dandy. These codes aren't related to overheating. The test I mentioned involves drawing air from the radiator, while the engine is running, through a glass cylinder with two chambers partially-filled with a special dark blue liquid. If combustion gases are present, the liquid will turn bright yellow. Those gases can pool under the thermostat and prevent it from opening. Thermostats have to be hit with hot liquid. Hot air won't do it.
Wednesday, August 19th, 2015 AT 3:20 PM