P0221 on Chevrolet: How to Diagnose & Fix
Throttle/Pedal Position Sensor/Switch B Circuit Range/Performance
1 Chevrolet model · 1 documented issue · 1 critical · $100-$450 repair
P0221 on Chevrolet by model: symptoms, diagnosis and fix
Impalas frequently throw a cluster of warnings at once — 'Engine Power Reduced,' 'Service StabiliTrak,' and 'Service Traction Control' — that are usually one underlying drive-by-wire fault rather than three separate failures. The most common root cause is the electronic throttle body actuator (or the dual throttle-position sensors inside it) going out of range; the accelerator pedal position sensors can also disagree. Because the ECM cross-checks these dual sensors, any disagreement forces the car into limp-home mode with drastically reduced power. Carbon buildup on the throttle plate aggravates it, especially in cold weather.
Common Symptoms
- 'Engine Power Reduced' message with limp-home mode
- 'Service StabiliTrak' and 'Service Traction Control' lights together
- Sudden loss of acceleration
- Rough or surging idle, worse in cold weather
- Intermittent recovery after key cycle
How to Fix
Scan for throttle/pedal DTCs before replacing parts. Start by cleaning the throttle body (a frequent cause, cheap fix). If codes/symptoms persist, replace the electronic throttle body assembly (ACDelco 12670981 fits the 2012-2013 3.6L; verify the correct unit for your engine/year). Some 3.6L applications require a relearn/idle relearn after replacement. If the pedal sensors are at fault, replace the accelerator pedal position sensor assembly.
Sources for this issue (2)
P0221 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0221 mean on a Chevrolet?
P0221 stands for "Throttle/Pedal Position Sensor/Switch B Circuit Range/Performance." This code means the second throttle or accelerator pedal position sensor (circuit B) is sending a signal that is out of the expected range or does not track properly with the other sensor. Modern drive-by-wire systems use redundant sensors, and the computer compares them for agreement. When sensor B's voltage is implausible or inconsistent, this code sets. It can cause hesitation, surging, reduced power, or a forced limp mode for safety. On Chevrolet it is documented across 1 model: Impala.
What are the most common causes of P0221?
The most common causes of P0221 are: Faulty throttle position sensor (sensor B), Faulty accelerator pedal position sensor, Dirty or worn throttle body, Wiring or connector problems (corrosion, chafing), Poor ground or reference voltage to the sensor, Intermittent open or short in the signal circuit, Faulty PCM/ECM (rare). The specific cause varies by vehicle.
How much does it cost to fix P0221 on a Chevrolet?
Published repair estimates on Chevrolet range from $100 to $450 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.