What is an Exhaust gas temperature sensor?
An exhaust gas temperature sensor measures the temperature of the exhaust gas. This information is then relayed back to the engine control unit or ECU, where the appropriate action is taken. In petrol engines, its main role is to protect key components from the higher temperatures common with downsized engines – so if the sensor detects excessive temperatures, the ECU will reduce the temperature, by lowering boost pressure in the case of the turbocharger.
In diesel engines, exhaust gas temperature sensors are also used to monitor the temperature of the diesel particulate filter (DPF) to establish the correct temperature for regeneration, reducing harmful emissions. It is not uncommon to have three or more sensors fitted to the exhaust; one prior to the turbocharger, one before the DPF and the third after the particulate filter