P0121: Throttle/Pedal Position Sensor Circuit Range/Performance
9 vehicles · 5 makes · $50-$900 repair
Most Reported On
P0121 is an OBD-II diagnostic trouble code meaning “Throttle/Pedal Position Sensor Circuit Range/Performance.” This code means the throttle position (or accelerator pedal position) sensor's signal does not match what the computer expects compared with other inputs like airflow, RPM, and the second throttle/pedal sensor. The sensor tells the computer how far the throttle or pedal is open; when its range or performance is off, the computer can't trust how much power you're requesting. You may notice hesitation, surging, poor acceleration, rough idle, or the vehicle dropping into a reduced-power 'limp' mode. It indicates an out-of-range or implausible signal rather than a complete loss of signal. This code is most commonly reported on 2014-2021 Ford Transit Connect, 2000-2004 Volvo V40, and 1999-2002 Volvo V70, plus 6 other vehicles, with repair costs ranging from $50 to $900.
Common Causes
Typical Repair Cost
Based on 10 documented vehicle-specific issues. Actual cost depends on root cause and vehicle.
Diagnostic Tools
To diagnose P0121, you'll need an OBD-II scanner. Here are our recommendations at every price point.
ANCEL AD310 Classic OBD-II Scanner
by ANCEL
A simple, affordable code reader that reads and clears check engine codes. Great for quick diagnostics on any OBD-II vehicle (1996+).
- Read & clear engine codes
- View freeze frame data
- I/M readiness status
- No batteries or app needed
BlueDriver Pro Bluetooth Scanner
by BlueDriver
Bluetooth OBD-II scanner with a free companion app. Provides enhanced diagnostics, smog readiness, and repair reports sourced from a database of verified fixes.
- Enhanced diagnostics (ABS, SRS, transmission)
- Repair Reports with verified fixes
- Smog check readiness
- Free app (iOS & Android)
LAUNCH CRP123X OBD-II Scanner
by LAUNCH
A professional-grade handheld scanner that reads all four major systems (engine, transmission, ABS, SRS) with live data streaming and graphing.
- Engine, transmission, ABS, SRS diagnostics
- Live data stream & graphing
- AutoVIN for vehicle identification
- Free lifetime updates via Wi-Fi
Autel MaxiCOM MK808S Diagnostic Tool
by Autel
Shop-level diagnostic tablet with bi-directional control, active tests, and full system coverage. Ideal for serious DIYers and small shops.
- All-system diagnostics (25+ modules)
- Bi-directional control & active tests
- Oil reset, EPB, BMS, TPMS, injector coding
- 7-inch touchscreen with Android OS
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Vehicles Affected (9)
Electronic Throttle Module (ETM) Failure
Electronic Throttle Module (ETM) Failure
Electronic Throttle Module (ETM) Failure
Electronic Throttle Module (ETM) Failure
Electronic Throttle Module (ETM) Failure
FAQ
What does P0121 mean?
P0121 stands for "Throttle/Pedal Position Sensor Circuit Range/Performance." This code means the throttle position (or accelerator pedal position) sensor's signal does not match what the computer expects compared with other inputs like airflow, RPM, and the second throttle/pedal sensor. The sensor tells the computer how far the throttle or pedal is open; when its range or performance is off, the computer can't trust how much power you're requesting. You may notice hesitation, surging, poor acceleration, rough idle, or the vehicle dropping into a reduced-power 'limp' mode. It indicates an out-of-range or implausible signal rather than a complete loss of signal.
What are the most common causes of P0121?
The most common causes of P0121 are: Worn or failing throttle position sensor, Dirty or carboned-up throttle body affecting plate position, Damaged, frayed, or shorted sensor wiring, Corroded or loose sensor connector, Poor sensor ground or reference voltage, Faulty throttle body / electronic throttle actuator, Mismatch between the two throttle or pedal sensor signals. The specific cause varies by vehicle.
How much does it cost to fix P0121?
Repair costs for P0121 range from $50 to $900, depending on the vehicle and root cause.
Which vehicles are affected by P0121?
Au7o has documented P0121 across 9 vehicle models from 5 manufacturers: Chevrolet, Ford, Jeep, Pontiac, Volvo.
Sources (9)
- ForumG6 'Engine Power Reduced' Message - Pontiac G6 Forum
- Forumfixed at last! P0121, P2135, reduced engine power - Pontiac Owners Group
- articleP2135 Pontiac: Meaning, Causes, Symptoms (engine-codes.com)
- ForumThrottle Body** Red Lightning Bolt** Limp Mode — JK-Forum.com
- ForumElectronic Throttle Control problem solved? — Jeep Wrangler Forum
- articleThrottle Position Sensor May Fail: Jeep Wrangler — RepairPal
- ForumThrottle position sensor (TPS) went bad, now what? — Jeep Wrangler TJ Forum
- ForumReduced Engine Power and Service Stability Control / Throttle Body issue — Impala Forums
- Forum2011 Chevy Impala - Service Stabilitrak - Reduced Engine Power — Edmunds
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.