Theory of Operation

WARNING: This page is about a different car, the 2011 RAM Cab & Chassis. 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 Boost Pressure Sensor is used to measure pressure in the intake manifold. The Powertrain Control Module (PCM) provides a 5-Volt supply and sensor ground for the Boost Pressure Sensor. The Boost Pressure Sensor provides a signal back to the PCM on the Boost Pressure Sensor Signal circuit. The PCM will detect a low signal voltage at operating conditions such as during an idle or a deceleration. The PCM will detect a high signal voltage during high engine load operating conditions. At key on, the readings for the Boost Pressure Sensor, Exhaust Gas Pressure Sensor, and Barometric Pressure Sensor are compared. This fault code occurs if the boost pressure reading is different from the others. During normal engine operation, the PCM estimates the Boost Pressure Sensor value using other fuel system related inputs. The PCM compares the actual Boost Pressure Sensor reading to this estimated value. If the two values are out of range for a calibrated period of time, an error is recorded. The key-on portion of the rationality will light the MIL immediately after the diagnostic runs and fails. The rationality portion will light the MIL immediately and the ETC lamp will also be illuminated. The PCM turns off the MIL when the diagnostic runs and passes in four consecutive drive cycles.