Theory Of Operation

WARNING: This page is about a different variant/trim than selected.

The PCM detects there is an overboost condition when various sensor inputs indicate there should be a specific amount of boost from the Turbocharger during various conditions, but the Boost Pressure Sensor value is above those expectations. There are many possible reasons for this condition (listed in the Possible Causes Table below).

There are two separate approaches used for this monitor: The Standard Heat-Up (SHU) and the Rapid Heat-Up (RHU). Fuel economy and emissions are improved when the engine is allowed to reach a higher temperature. Engine performance and torque are increased when the engine is running at a cooler temperature. The PCM determines which heat-up mode to use based on various conditions.

The PCM uses the P0234-00 monitor when there is an underboost occurrence during the SHU mode.

The PCM uses the P2D30-00 monitor when there is an underboost occurrence during the RHU mode.

Because the PCM switches between SHU and RHU mode, both DTCs may be present when underboost is detected. Both DTCs have the same Diagnostic content.