What Does It Mean?
This is a generic powertrain diagnostic trouble code (DTC) that generally applies to OBD-II vehicles. This may include, but is not limited to, Land Rover (Range Rover, Discovery), Ford, Chevrolet, Mazda, Dodge, Peugeot, Saab, Toyota vehicles, etc.
Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.
If your OBD-II equipped vehicle has stored a P023D code, it means the powertrain control module (PCM) has detected a discrepancy in the correlation signals between the manifold absolute pressure (MAP) sensor and the turbocharger/supercharger boost pressure sensor that has been designated “A”.
The “A” designates a specific boost pressure sensor in a system that may use multiple boost pressure sensors at different locations. Consult a reliable vehicle information source to accurately determine which sensor the A references (for the vehicle in question). This code applies only to vehicles equipped with forced air induction devices. Forced air induction devices include turbochargers and superchargers.
The MAP sensor provides the PCM with a voltage signal that reflects the density or pressure of the air in the intake manifold. The voltage signal is received (by the PCM) as kilopascal (kPa) units or inches of mercury (Hg). In some vehicle applications, the MAP replaces barometric pressure and is measured in similar increments.
The turbocharger/supercharger boost pressure sensor (designated A) will likely be of a similar design to the MAP sensor. It monitors the air density (boost pressure) inside the turbocharger/supercharger intake pipe and provides the PCM with an appropriate voltage signal.
A P023D code will be stored and a malfunction indicator lamp (MIL) may be illuminated if the PCM detects voltage signals between the MAP sensor and the turbocharger/supercharger boost pressure sensor A that differ by more than a programmed degree. Multiple ignition cycles (with a failure) may be required for MIL illumination.
How severe is this DTC?
Overall engine performance and fuel economy can be affected by the conditions contributing to a P023D code. It should be classified as severe.
What are some of the symptoms of the code?
Symptoms of a P023D trouble code may include:
Decreased engine performance
Excessively rich or lean exhaust
Delayed engine start (especially when cold)
Reduced fuel economy
What are some of the common causes of the code?
Causes
of this P023D trouble code may include:
Faulty MAP / turbocharger / supercharger boost pressure sensor A
Open or shorted MAP or turbocharger / supercharger boost pressure sensor A wiring or connector
Engine malfunction (insufficient vacuum production)
Restricted intercooler
PCM programming error or PCM fault
What are the P023D troubleshooting steps?
I would first want access to a diagnostic scanner, a digital volt/ohmmeter (DVOM), a manual vacuum pressure gauge, and a reliable vehicle information source before attempting to diagnose a P023D code. Diagnosing any MAP sensor-related code should include verifying that the engine is producing sufficient vacuum. This can be done using the vacuum pressure gauge.
A visual inspection of all wiring and connectors for the MAP / turbocharger / supercharger boost pressure sensor system is necessary if there is no intercooler obstruction and the air filter is relatively clean. Perform necessary repairs. Then, I would connect the scanner to the vehicle’s diagnostic port and retrieve all stored codes and freeze frame data. Freeze frame data could be described as a snapshot of the exact circumstances occurring at the time of the malfunction that led to the stored P023D code. I like to note this information as it may be helpful as the diagnosis progresses. Now, clear the codes and test drive the vehicle to see if the code resets.
If it does:
Test the individual MAP / turbocharger / supercharger boost pressure sensors using the DVOM and your vehicle information source
Set the DVOM to the ohms setting and test the sensors when they are disconnected
Consult your vehicle information source for component testing specifications
MAP / turbocharger / supercharger boost pressure sensors that do not meet manufacturer specifications must be replaced
If all sensors meet manufacturer specifications:
Test the reference voltage (usually 5 volts) and a ground at the sensor connectors
Use the DVOM and connect the positive test lead to the reference voltage pin of the sensor connector with the negative test lead connected to the ground pin of the connector
If you find reference voltage and ground:
Reconnect the sensor and test the sensor signal circuit with the engine running
Follow the temperature to voltage chart found in the vehicle information source to determine if the respective sensors are functioning correctly
Sensors that do not reflect the specified voltage degree (according to manifold absolute pressure and turbocharger/supercharger boost pressure) specified by the manufacturer must be replaced
If the sensor signal circuit reflects the correct voltage degree:
Test the signal circuit (for the sensor in question) at the PCM connector. If there is a sensor signal at the sensor connector and none at the PCM connector, there is an open circuit between the two components
Test the individual system circuits using the DVOM. Disconnect the PCM (and any associated controllers) and follow the diagnostic flowchart or connector pin diagrams to test the resistance and/or continuity of the individual circuit
Suspect PCM fault or PCM programming error if all MAP / turbocharger / supercharger boost pressure sensors and circuits meet specifications.
Consult Technical Service Bulletins (TSBs) for assistance with your diagnosis
The turbocharger/supercharger boost pressure sensor is often left disconnected after air filter replacement and other related maintenance operations