What does it mean?
OBD II fault code P023A is a generic trouble code that is defined by carmaker Alfa-Romeo as P023A – “Charge Air Cooler Coolant Pump Control Circuit/Open”, and is set when the PCM (Powertrain Control Module) detects a) a defect, failure or malfunction that causes an open circuit in the control circuits(s) of the pump that circulates coolant through the charge air cooler. Note that charge air coolers are also known as “intercoolers”.
The sole function of the charge air cooler is to reduce the temperature of the compressed air that is forced into the engine, based on the principle that since cool air is denser than hot air more air can be “packed” into the cylinders than hot air.
However, since compressing air using a turbocharger increases the temperature of the intake air, the hot air is passed through a charge air cooler, aka “intercooler” to lower the temperature of the intake air to improve engine performance while reducing both fuel consumption and emission levels, at the same time.
In terms of operating principles, the charge air cooler on most, if not all Alfa Romeo models, is built into the intake manifold in the form of a kind of box through which liquid coolant can be circulated by a dedicated coolant pump. Thus, since parts of the intake runners are in direct contact with the circulating coolant, the coolant absorbs some of the high heat energy of the intake air through the walls of the intake runners.
The hot coolant then passes through a dedicated heat exchanger, or radiator that sheds the collected heat energy to the atmosphere. In practice, this cooling system works much like the engine cooling system, but it is important to note that the charge air cooling system works independently of the engine cooling system.
It is also important to note that the correct functioning of the charge air cooling system is critically important for smooth and proper engine operation since the PCM uses the temperature of the intake air as measured after the charge air cooler to calculate fuel delivery strategies that suit the current engine operating conditions at all times.
Put differently, this means that since cool air is denser than hot air, the PCM uses both the density of the intake air (based on its temperature) and the volume of intake air (as reported by the Mass Airflow Sensor) to calculate how much fuel to add to the intake air to create an air/fuel mixture that is as close as possible to a stoichiometric ratio. In the case of gasoline, a stoichiometric ratio is one part of fuel to every 14.7 parts of air.
In this ratio, all the fuel in the mixture is combusted using all available air in a combustion process that extracts the maximum amount of energy from the fuel. This process maximizes engine performance and keeps exhaust emissions within allowable limits.
From the above, it should be clear that efficient management of the intake air temperature plays a critical role in the overall engine and fuel management systems and if a fault or defect such as an open electrical circuit in the charge air cooling system occurs, the PCM will recognize that it cannot perform several critically important engine management functions effectively. When this happens, the PCM will set an appropriate fault code and also illuminate a warning light.