Circuit/System Description

The exhaust gas temperature sensors are variable resistors that measure the temperature of the exhaust gas at the inlet and outlet of the diesel particulate filter (DPF). The engine control module (ECM) supplies a bias 5-volt signal to the EGT signal circuit, and supplies a ground to the low reference circuit. When the EGT sensor is cold, the sensor resistance is low. When the EGT temperature increases, the sensor resistance increases. With high sensor resistance, the ECM detects a higher voltage on the EGT signal circuit. With lower sensor resistance, the ECM detects a lower voltage on the EGT signal circuit.