P0221 code: Throttle/Pedal Position Sensor B Range/Performance
P0221 means throttle/Pedal Position Sensor B Range/Performance. The code says where to look, not what failed — the fix depends on which cause your car actually has.
What P0221 means
Modern electronic throttle systems use two position sensors ('A' and 'B') on the throttle body or pedal so the computer can cross-check them. P0221 sets when sensor B's signal is out of its expected range or doesn't track plausibly against sensor A and actual engine load. Unlike a hard circuit code, this is a 'the signal exists but doesn't make sense' fault — a worn sensor track, a connector with corroded pins, or wiring with intermittent resistance are typical causes. On most electronic throttle bodies the sensors are built in, so a bad sensor B often means replacing the throttle body (or the pedal assembly, if B lives on the pedal in your vehicle). Because the computer can no longer fully trust the throttle reading, many cars respond by limiting power (limp mode) until the fault is fixed.
P0221 symptoms
- Reduced-power or 'limp' mode with limited acceleration
- Hesitation, surging, or erratic throttle response
- Rough or unstable idle
- Intermittent symptoms that come and go with bumps or temperature
- Check-engine light
What it costs to fix P0221
Typical range: $50–$600 · about ~0.3–1.5 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Connector / wiring repair | $10–$120 | ~0.5–1.5 hrs |
| Throttle position sensor (where separately replaceable) | $40–$200 | ~0.3–1 hrs |
| Electronic throttle body (sensors integrated) | $150–$500 | ~0.5–1.5 hrs |
On older cable-throttle engines the TPS is a cheap bolt-on sensor; on most modern electronic throttles the sensors are sealed inside the throttle body, pushing the cost up. Always rule out the connector and wiring first — they're the cheap fix.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0221 for my exact vehicle →
How to fix P0221
Moderate — doable at home with common tools and patience
- Pull codes and confirm which unit holds sensor B
Record freeze-frame data and any companion throttle or pedal codes. On most vehicles throttle position sensor B is part of the electronic throttle body, but on some it's in the pedal; the service information for your vehicle settles which part you're actually diagnosing before you look at any wiring.
- Graph sensors A and B together through a slow sweep
Key on, engine off, press the pedal slowly from rest to the floor while graphing both sensor voltages. Depending on design they move in opposite directions or in parallel with a fixed offset — what matters is that the relationship holds everywhere. A glitch, flat spot, or drift in B alone marks where its track is worn.
- Flex the harness with the graph still running
Gently move the throttle body harness, then the pedal harness under the dash, while watching B's trace. A plausibility fault caused by an intermittent pin or a wire broken inside its insulation shows up as a spike on B the moment you disturb the right spot.
- Check sensor B's reference and ground under load
Back-probe the reference and ground at the connector with everything plugged in. Excess voltage drop on the ground, or a reference that sags slightly, can bend B's signal just enough to fail the correlation check without setting a hard circuit code. Clean or repair any connection that reads poorly.
- Replace the assembly and run the throttle relearn
If B's trace is faulty with good wiring, replace the throttle body or pedal assembly, since the sensors aren't sold separately on most designs; some budget throttle bodies bring correlation codes right back. Complete the relearn per the service manual, and keep fingers out of the bore with the key on — the plate can snap shut.
DIY or shop? A home mechanic with a scan tool that graphs two signals at once can diagnose P0221 thoroughly, and both the connector work and a pedal-assembly swap are simple. A throttle body replacement is still bolt-on, but many vehicles won't clear reduced power until a relearn is done, and some need a dealer-level scan tool for it. If the car is in limp mode with unpredictable throttle response, have it brought in rather than driven.
Tools for the DIY steps: Scan tool that graphs two sensors at once · Digital multimeter with back-probe pins · Socket set and Torx bits · Electrical contact cleaner · Flashlight for under-dash work
Not sure which step applies to your car? Get the likely cause for your exact vehicle before buying anything for P0221.
Start a case with P0221 and your car. Redline weighs these causes against what your car shows, and names the check that would settle it before you buy parts.
Can I drive with P0221?
Redline can’t determine from a symptom or code alone whether your car is safe to drive.
P0221: common questions
Why did my car go into reduced-power mode with P0221?
The computer cross-checks two throttle sensors, and when sensor B stops tracking sensibly it can no longer trust the throttle reading. Limiting power is a deliberate safety response — it prevents an untrusted throttle from accelerating the car unexpectedly.
Is P0221 the sensor or the wiring?
Either. A worn sensor track inside the throttle body is common, but a corroded connector or intermittent wiring produces the same 'implausible signal' fault for far less money. Watching sensor A and B on a scan tool while wiggling the harness is a quick way to tell.
What's the difference between P0221 and P0121?
Same type of fault, different sensor: P0121 is a range/performance problem on sensor A, P0221 is the same problem on sensor B. Both sensors usually live in the same throttle body or pedal assembly, so the diagnosis is similar.
Can I just clean the throttle body for P0221?
Cleaning helps codes caused by carbon binding the throttle plate, but P0221 is a sensor-signal fault — cleaning rarely fixes a worn sensor track. It's still worth cleaning the connector contacts and checking the wiring before buying a throttle body.
Related trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P0221 from your phone. See our guide to the best OBD2 Bluetooth adapters. Run a repair shop? See Redline for shops.
Generic OBD-II reference. Manufacturer-specific behavior varies. Confirm with a scan tool and, for safety-related codes, a professional inspection. Cost ranges are reference ranges, not quotes.
Seeing P0221 on your car?
Every problem becomes a Case. Tell Redline what the car is doing: it shows what the evidence supports, what’s still missing, and what to check next, before you approve a repair.
“Inner pad ~1 mm. Outer pad 3 mm.”
Next: check the slide pins move freely before buying parts.