Throttle Position Sensor 1 - Voltage Below Normal
Throttle position sensor voltage is too low.
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What it means (plain English)
The throttle position sensor measures how far the gas pedal is pressed down. When the signal it sends to the engine computer is lower than expected, it thinks the throttle is more closed than it actually is. It should be sending between 0.5 to 4.5 volts depending on pedal position. If it drops below 0.3 volts or stays around 0 volts, you’ll get this code.
What the computer is actually seeing
The engine control module (ECM) expects a voltage signal from the throttle position sensor between 0.5 to 4.5 volts. When it sees a voltage under 0.3 volts, it sets this fault code.
What a healthy reading looks like
Normal throttle position sensor voltage should be between 0.5V and 4.5V, depending on the throttle position.
Guided diagnostic — the DiagCoach way
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.
- 1Check the wiring and connector to the throttle position sensor for damage or corrosion—repair as needed.
- 2With the key on, check the voltage at the throttle position sensor connector. You should see between 0.5V and 4.5V. If not, go to step 3.
- 3Inspect the throttle position sensor itself by testing it with a multimeter. If the sensor does not respond correctly when you throttle up and down, replace the sensor.
- 4If the sensor is behaving correctly, inspect the wiring harness between the ECM and throttle position sensor for shorts or opens. Repair any issues found.
Common causes
- Faulty throttle position sensor
- Wiring issue or connector problem
- Faulty engine control module (ECM)
- Electrical short or open circuit
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's generally safe, but expect reduced engine performance and responsiveness, so fix it soon.
What happens if I ignore this code?
Ignoring it can lead to poor engine performance and possibly cause more damage if other components get stressed.
Why do I see this code along with SPN 4126?
SPN 4126 is related to the throttle position sensor too; they often trigger together due to the sensor’s function.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
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