Throttle Position Sensor - Signal Abnormality

The engine control unit (ECU) is getting a throttle position reading that doesn't make sense, like 0.1 volts when it should be around 0.5 to 4.5 volts as you press the gas pedal.

The ECU monitors the throttle position sensor to determine how much air is entering the engine based on the driver's input. If the sensor output is suddenly too low or high, like less than 0.2 volts or more than 4.8 volts, or it doesn't change as expected when the pedal is pressed, it triggers SPN 3158.

Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.

1. 1Check the throttle position sensor connector for loose or corroded pins.
2. 2Inspect the wiring between the throttle position sensor and the ECU for continuity and shorts.
3. 3With a multimeter, measure voltage at the throttle position sensor. At idle, you should see around 0.5 volts; at full throttle, it should be about 4.5 volts. If it's out of this range, the sensor may be faulty.
4. 4Check for any mechanical binding in the throttle linkage or any vacuum leaks around the throttle body.
5. 5If the wiring and sensor check out, further investigate the ECU for malfunctions.

• Faulty throttle position sensor
• Wiring issues (shorts or opens) in the throttle position circuit
• Poor electrical connections or corrosion at the connector
• Mechanical binding in the throttle linkage
• Vacuum leaks affecting the throttle operation

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