Circuit/System Description

The exhaust gas recirculation (EGR) cooler must remain within a specific temperature range to efficiently reduce emissions. Engine coolant flowing through the EGR cooler helps cool the exhaust gases flowing to the EGR valve. The EGR cooler has internal coolant passages and metal fins between the passages to help carry away excessive exhaust gas heat. This diagnostic monitors the temperature of the EGR cooler by monitoring both EGR temperature sensors while the EGR valve is active. If the EGR cooler temperatures exceed a calibrated threshold, this diagnostic will run and fail.