P2128
Throttle/Pedal Position Sensor/Switch E Circuit High
Throttle control (drive-by-wire)
Generic OBD-II
Medium
What it means
P2128 means the ECM sees an abnormally high voltage on the 'E' throttle/accelerator-pedal position sensor circuit — higher than the sensor should ever produce. It usually comes from a short to voltage, an open ground, or a failing sensor. Because the ECM relies on this signal to interpret how far you press the pedal, it may cut the engine to reduced-power mode when the signal can't be trusted.
Medium
Can I keep driving? Often drivable, but the pedal signal may be rejected and the car put into reduced-power mode; repair before relying on it in traffic.
Common symptoms
What you'll notice
- Check-engine light on
- Reduced power or 'limp' (failsafe) mode
- Poor or unresponsive throttle response to the pedal
- Rough or unstable idle
Common causes
Most likely first
- Faulty accelerator/throttle position sensor (E element)Likely
- Signal wire shorted to voltage or an open in the sensor circuitCommon
- Poor connection or corrosion at the pedal/throttle sensor connectorCommon
- 5-volt reference or ground fault feeding the sensorLess often
- Failing ECM/PCMLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and note related pedal/throttle codes (P2127, P2138).
- Inspect the pedal or throttle sensor connector and wiring for damage, corrosion, or a short to power.
- With the key on, verify a steady 5-volt reference and good ground at the sensor connector.
- Back-probe the E signal circuit and compare readings against spec through pedal travel.
- Replace the pedal/throttle position sensor if it reads high or erratic; suspect the ECM only after wiring is confirmed good.
FAQ
Quick answers
Is it safe to drive with P2128?+
Only cautiously — the engine may drop to reduced power with little throttle response, so avoid situations where you need to accelerate quickly until it's fixed.
Can I just clear P2128?+
It will clear, but a high signal from a wiring or sensor fault will set it again, usually quickly.
Related codes
Often seen with P2128
Read & clear P2128 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX