DTC code
P1121
Throttle Position (TP) Sensor Circuit Intermittent High Voltage
Technical guide
Symptoms
- Check engine light
- hesitation or stumbling during acceleration
- erratic throttle response and unpredictable idle behavior
- rough idle
- engine stalling
- possible reduced-power/limp mode
- poor fuel economy.
Probable causes
- Faulty throttle position sensor
- intermittent short to power or damaged/corroded wiring in the TP sensor circuit
- loose or disconnected connector
- poor ground connection
- on Ford
- a faulty MAF sensor causing the TP/MAF inconsistency
- on Toyota Prius (2004-2009)
- a stuck coolant flow control valve.
Diagnostic steps
- Confirm the exact code definition for the vehicle make - P1121 is manufacturer-specific.
- Scan for codes and record freeze frame data.
- Visually inspect the throttle position sensor for physical damage, mounting or alignment problems.
- Inspect the TP sensor wiring and connector for damage, corrosion, looseness and shorts to power; check the ground connection.
- With a scan tool, monitor the TP sensor signal voltage live while sweeping the throttle through its full range, watching for intermittent spikes or dropouts.
- On Ford applications, compare TP and MAF sensor data for consistency and test the MAF sensor.
- If wiring and connectors test good, replace the throttle position sensor.
- Clear codes and road test to confirm the repair.
Cross-checked technical synthesis (QA). It does not replace the manufacturer's procedure.
Models most reported with this code (NHTSA)
Count of distinct owner complaints mentioning the code. US data — same engines, same failures.
AI here is a librarian: this page shows only what mechanics confirmed, or says “unknown”. It never suggests a diagnosis — MECCANIC interprets the code, never your car.
0 confirmed cases on P1121
Nothing confirmed yet for this code. No guess is offered on purpose.
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