OBD-II trouble code
P0221: Throttle/Pedal Position Sensor/Switch 'B' Circuit Range/Performance
The second throttle or accelerator pedal position sensor is reporting a value that doesn't line up with the other sensors. The check engine light is on and the vehicle may drop into a reduced-power 'limp' mode.
Quick facts
- System
- Powertrain
- Category
- Throttle / Idle
- Severity
- Medium severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $100 – $600
- DIY difficulty
- Intermediate DIY
Browse every code in P0200–P0299, or start from the full code library.
What does P0221 mean?
Modern drive-by-wire vehicles have no throttle cable. Instead, the accelerator pedal and the throttle body each carry two or three position sensors that report their angle to the powertrain control module (PCM) as separate voltage signals — labeled 'A', 'B', and sometimes 'C'. The redundancy is a safety feature: the PCM continuously compares the signals against one another so a single failed sensor can't command unintended throttle.
P0221 sets when the 'B' signal is present but doesn't correlate correctly with the others — its voltage moves out of the expected range for a given pedal or throttle position, or it responds too slowly or erratically. Unlike a hard circuit fault (short or open), this is a 'range/performance' code, meaning the signal exists but the PCM doesn't trust its value.
Because throttle demand is safety-critical, a 'B' correlation fault commonly puts the vehicle into a fail-safe or 'limp' mode: throttle response is limited, the engine may be capped at a low RPM, and cruise control is usually disabled. How far that goes varies by manufacturer, and some vehicles only light the lamp until the fault repeats, so treat limp mode as the likely response rather than a certainty. Where it does engage, the car stays driveable but sluggish. The usual causes are a worn sensor inside the pedal assembly or throttle body, wiring and connector problems, or carbon buildup that keeps the throttle plate from moving where it's commanded.
Common causes
- Worn or failing 'B' sensor inside the accelerator pedal position (APP) assembly
- Worn or failing throttle position sensor inside the throttle body
- Corroded, loose, or damaged connector at the pedal or throttle body
- Chafed or broken wiring in the sensor signal, reference, or ground circuit
- Carbon buildup causing the throttle plate to bind or stick
- Poor sensor ground or an out-of-spec 5-volt reference from the PCM
- Rarely, a failing PCM
Symptoms
- Check engine light is on
- Reduced engine power or a 'limp' / fail-safe mode
- Hesitation, surging, or unstable idle
- Delayed or erratic throttle response
- Cruise control disabled
- Occasional stalling
Diagnostic steps
- 1.Scan for companion codes. A P0221 alongside P0222/P0223 or throttle 'A' codes (P0121-P0123) helps localize whether the fault is at the pedal or the throttle body.
- 2.With a scan tool, watch the live 'A' and 'B' sensor percentages while slowly pressing the pedal. They should track together in a fixed relationship; a signal that lags, jumps, or flatlines is the suspect.
- 3.Inspect the pedal and throttle-body connectors for corrosion, bent pins, and looseness; reseat them and re-test.
- 4.With the ignition on and the engine off, back-probe the 'B' circuit for the correct 5-volt reference and a clean ground; wiggle-test the harness for intermittent readings.
- 5.With the ignition off and the key out, inspect the throttle plate for carbon buildup that could keep it from reaching its commanded position. Do not lever an electronic throttle plate open by hand — the return spring and gear train are not built for it and the integrated sensors can be disturbed — and use a cleaner rated for coated plates, since scrubbing the coating away causes idle faults of its own. Expect a throttle relearn afterwards.
- 6.If wiring and grounds are good but one sensor's signal is out of range, replace the affected pedal assembly or throttle body and perform any required throttle relearn.
Repair cost
$100 – $600
Diagnosis runs $75-$150. An accelerator pedal position sensor assembly is typically $150-$350 installed; a throttle body with an integrated sensor runs $250-$600 installed. Wiring or connector repairs can be much cheaper. Many vehicles require a throttle relearn procedure after the repair.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with accelerator pedal position sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.