P2135: Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation

Common causes

• Worn or failing position sensors inside the electronic throttle body
• A loose, corroded or damaged connector or wiring at the throttle body
• A problem with the shared 5-volt reference or ground circuit
• On some vehicles, a faulty accelerator pedal position sensor

Code meanings can vary slightly by manufacturer. Use these as a starting point and confirm with your vehicle's service information or a mechanic before replacing parts.

Symptoms

• Reduced power or limp mode
• Throttle that doesn't respond or responds erratically
• Stalling or rough idle
• Check engine and sometimes a wrench or electronic throttle light

Is it safe to drive?

With reduced power, a throttle that doesn't respond properly, or stalling, the car isn't safe to drive in traffic; pull over safely and have it towed. Even if it seems normal with a steady light, get it diagnosed promptly because limp mode can come on suddenly.

How to check it with a scanner

1. Plug an OBD2 scanner into the port under the dashboard and read all stored codes and the freeze-frame data (the conditions when the code set).
2. With the key off, inspect the throttle body connector and wiring for corrosion, damage or a loose fit.
3. With the key on and engine off, watch both throttle position readings in live data while slowly pressing the pedal; they should move smoothly together with no jumps or dropouts. The throttle plate moves with the key on, so keep fingers out of the throttle body.
4. Check for other codes, especially sensor reference voltage and pedal position codes.
5. After replacing a throttle body, perform your vehicle's throttle relearn procedure.
6. After a repair, clear the code and drive normally for a few days to confirm it doesn't come back.

A basic code reader shows the code; scanners with live data let you watch sensor readings, which is what you need for most of the checks above. See OBD2 scanners under $100.

Questions

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• P0121: Throttle position sensor A out of range
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