Theory of Operation

WARNING: This page is about a different car, the 2011 RAM Pickup. However, it is still accessible from the selected car via links, so may be relevant.

The Charge Air Cooler Temperature Sensor (CAC) and the Boost Pressure Sensor are combined in one sensor and are located near the EGR Airflow Throttle Control Valve. The Powertrain Control Module (PCM) provides a 5-Volt reference voltage to the sensor. The PCM monitors the temperature of the air entering the intake using the CAC Temperature Sensor. At key-on after an eight hour cold soak, the CAC Temperature Sensor is compared to the EGR Orifice Temperature Sensor and Coolant Temperature Sensor readings. If the temperatures differ more than a calibrated amount, a DTC is recorded. In the case that all four sensor values are distributed over a range of temperatures this diagnostic will not run. A block heater is one possible cause of such a condition. The key on monitor is disabled for ambient temperatures below 20°F. The rationality check looks at the temperature reading from the CAC Temperature Sensor over time and ensures that it changes. This monitor is used to verify the sensor is responding with temperature change. Both the key-on and rationality errors require that the diagnostic fails in two consecutive drive cycles before the MIL lamp is lit. The PCM turns off the MIL lamp when the diagnostic runs and passes in four consecutive drive cycles.