The Honda OBD1 ECU processes Throttle Position Sensor (TPS) input as an 8-bit value. This value represents the voltage signal converted into a digital range.

Calculation Formula#

To convert a raw 8-bit hexadecimal TPS value into a percentage, use the following formula:

TPS(x) = (HexToDec(x) / 229.5) * 100

Where:

• x: The raw 8-bit hexadecimal value from the ECU.
• HexToDec(x): The decimal equivalent of the hexadecimal input.

Wide Open Throttle (WOT) Reference#

At Wide Open Throttle (WOT), the sensor outputs approximately 4.5V. The ECU maps this voltage to the 8-bit digital range as follows:

• Voltage: 4.5V
• Calculation: (4.5V / 5.0V) * 255 = 229.5
• Result: 229.5 (Decimal) represents 100% throttle position.

Note

The value 229.5 is the theoretical maximum for the 8-bit TPS range in the OBD1 ECU architecture. Values exceeding this may indicate sensor calibration issues or wiring faults.