Inside your Chevrolet’s accelerator pedal position sensor (APPS), there are two or more sensors. The engine control unit (ECU) uses these to ensure accurate throttle input. Each sensor receives a different voltage from the ECU: Sensor E receives half the voltage of Sensor D, resulting in half the output voltage. This acts as a crucial fail-safe mechanism.
Most APPS utilize an incremental voltage system. As you press the pedal, the voltage sent to the ECU increases, similar to a throttle position sensor.
The ECU utilizes this voltage difference for diagnostics. It expects Sensor E’s voltage to be precisely half of Sensor D’s. A simple formula governs this relationship: Sensor E x 2 = Sensor D. For instance, if Sensor E reads 1.5 volts, Sensor D should read around 3 volts, allowing for a minor variance of approximately 50 mV.
This system allows the ECU to detect faults within the APPS circuit. If a discrepancy exceeding 50 mV (often 100 mV triggers a fault) occurs between the two sensors, the ECU recognizes a problem. In Chevrolet vehicles with drive-by-wire throttle systems, this will likely trigger a “limp mode” for safety and illuminate a check engine light, indicating a specific Chevrolet Accelerator Pedal Obdii Code. This code alerts the driver to the issue and prompts further diagnosis.
Determining which sensor in a data logger represents 100% throttle can be done by applying full throttle and observing which sensor maxes out its reading. Sensor D typically represents the actual pedal position, but testing is recommended to confirm.
Remember, the accelerator pedal position is just one factor. The ECU adjusts the throttle position based on various factors like driving mode (sport, eco), road conditions, and engine load. Examining “Relative Throttle Position” (RTP), often displayed as a 0-100% value, can offer valuable insights into actual throttle opening. While “Absolute Throttle Position” includes the slight opening at idle, RTP focuses solely on driver-initiated throttle changes. Understanding these nuances can aid in diagnosing issues related to a chevrolet accelerator pedal obdii code.
