What does P1121 mean on a Chevy?

P1121. Throttle Position (TP) Sensor Circuit Intermittent High Voltage. Applies to Silverado, Sierra, Tahoe, Yukon, Avalanche.

What causes P1121 on a Chevy?

Worn TP sensor carbon track spiking voltage TP signal wire shorted to 5V reference Loose throttle body electrical connector Excessive throttle shaft play disturbing the sensor Water intrusion in the throttle body connector

How do I fix P1121 on a Chevy?

Sweep-test TP Sensor 1 and 2 on a Tech2 or GDS2 for dropouts Inspect the throttle body connector for moisture and corrosion Wiggle-test the TP harness during a slow pedal sweep Compare TP angle against accelerator pedal position for tracking errors Replace the throttle body assembly only if the sweep shows spikes, then perform the idle learn

Code

P1121

Throttle Position (TP) Sensor Circuit Intermittent High Voltage

Category: Powertrain - Computer and Auxiliary Controls
Severity: Check Engine Light
Applies to: Silverado, Sierra, Tahoe, Yukon, Avalanche
Related: No single generic twin. See OBD Codes List

What it means

P1121. Throttle Position (TP) Sensor Circuit Intermittent High Voltage. This Chevy-enhanced code applies to Silverado, Sierra, Tahoe, Yukon, Avalanche.

Findings, check these first

Worn TP sensor carbon track spiking voltage
TP signal wire shorted to 5V reference
Loose throttle body electrical connector
Excessive throttle shaft play disturbing the sensor
Water intrusion in the throttle body connector

Standard procedure

Sweep-test TP Sensor 1 and 2 on a Tech2 or GDS2 for dropouts
Inspect the throttle body connector for moisture and corrosion
Wiggle-test the TP harness during a slow pedal sweep
Compare TP angle against accelerator pedal position for tracking errors
Replace the throttle body assembly only if the sweep shows spikes, then perform the idle learn

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Sources and review

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Last updated 2026-09-13.

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