Throttle/Pedal Position Sensor/Switch B Circuit Low Input
The throttle position sensor B is sending a low voltage signal to the engine control module (ECM).
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
Inside the throttle body, the sensor that tracks how far you press the gas pedal is telling the computer it's not getting enough voltage, which can cause poor engine performance.
What the computer is actually seeing
The ECM expects to read a voltage level between 0.5 volts (closed throttle position) and 4.5 volts (wide open throttle). A reading below 0.5 volts triggers the P2127 code.
What a healthy reading looks like
Throttle position sensor B should provide a voltage between 0.5V to 4.5V based on pedal 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 throttle position sensor B wiring and connector for damage or corrosion.
- 2Measure the voltage at the throttle position sensor B connector with the key on, engine off. Expected voltage is between 0.5V and 4.5V. If it's below 0.5V, proceed to the next step.
- 3Inspect the throttle position sensor B for proper operation by checking resistance and comparing to manufacturer specifications. If out of spec, replace the sensor.
- 4Check for binding or mechanical issues in the throttle body; ensure it's free to move. If it's binding, clean or repair as needed.
- 5If all else checks out, test the ECM for faults or reprogramming if necessary.
Common causes
- Faulty throttle position sensor B
- Wiring issue (broken or shorted wires)
- Poor connector contact (corrosion or dirt)
- Faulty ECM
- Mechanical throttle binding or restrictions
Typical repair cost
$$
Related codes
Frequently asked questions
Can I drive the vehicle with this code?
It's drivable, but expect poor acceleration and possible stalling.
Will this problem come back after I fix it?
If all underlying issues are fixed, it should not return.
Why does this code show with a misfire code?
A bad throttle position sensor can affect air-fuel mixture, causing misfires.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
Start guided diagnostic →