The diagnostic trouble code P0108 is registered by your vehicle’s onboard computer when it detects an issue with the Manifold Absolute Pressure (MAP) sensor. Specifically, P0108 signifies “Manifold Absolute Pressure (MAP) sensor / Barometric pressure (BARO) sensor circuit high input.” This means the voltage signal from your MAP sensor is unusually high, indicating a potential problem that needs addressing.
The MAP sensor is crucial for engine management. It measures the pressure within the intake manifold, which reflects the engine’s load and air intake. Typically located on or near the throttle body, the MAP sensor works by sending pressure data as a voltage signal to the Powertrain Control Module (PCM) or Engine Control Module (ECM). This information, combined with readings from other sensors like the Intake Air Temperature (IAT) and Engine Coolant Temperature (ECT) sensors, allows the PCM/ECM to precisely regulate the engine’s air-fuel mixture and ignition timing for optimal performance and efficiency. In some vehicles, the MAP sensor’s role might be integrated with a Mass Air Flow (MAF) sensor.
When the PCM or ECM logs a P0108 code, it indicates that the voltage signal from the MAP sensor has exceeded a predetermined high threshold. If the sensor voltage remains above approximately 4.5 volts for an extended period (typically more than 10 seconds) while other engine parameters like oxygen sensor readings, engine speed (RPM), and throttle position are changing, the P0108 code is triggered. This abnormally high voltage suggests that the data being transmitted from the MAP sensor is not within the acceptable operating range for the engine, particularly in relation to the Throttle Position Sensor (TPS) input.
Alt text: Location of the Manifold Absolute Pressure Sensor in an engine bay, highlighting its proximity to the throttle body for accurate intake manifold pressure readings.
The consequences of a P0108 code can extend beyond just an illuminated check engine light. Faulty data from a malfunctioning MAP sensor can disrupt the fuel pump operation and ignition system, leading to various engine performance issues. These can include rough idling, decreased fuel economy, hesitation during acceleration, and even stalling. Addressing a P0108 code promptly is important to maintain your vehicle’s performance and prevent potential further engine damage. Diagnosing the root cause of the high voltage signal is the first step towards resolving this issue and ensuring your engine runs smoothly and efficiently.
