P0221: Throttle/Pedal Position Sensor/Switch B Circuit Range/Performance

With electronic throttle control the throttle body carries two position sensors, A and B, usually with opposite or offset signals, and the engine module compares them (correlation code P2135). GM and Ford give the pedal sensors their own codes (P2120 ff), so B is in practice the second throttle sensor. P0221 is the plausibility fault: the signal of sensor B is electrically valid but does not match sensor A or the throttle position expected from airflow. Bosch ME9 engines (Saab) set it at a deviation of more than 9 %, older Ford systems at more than 7 degrees between the sensors without the warning light; many newer engines report this only as P2135. The module carries on with sensor A, limits throttle opening and power and switches off cruise control.

High severity. Can I keep driving?Be careful: the car may suddenly lose power. If it goes into limp mode, get off the highway and calmly make your way to a repair shop.

Symptoms

Check engine light on
Limp mode, reduced power
Rough idle, jerking
Cruise control disabled

Most likely causes

Worn track of sensor B (signal jumps)
Contact resistance at connector or wiring
Throttle dirty or sticking
Mass airflow sensor fault or false air

What to check, in order

Start with the simplest. You can tick off each step.

Check the pedal and throttle connectors
Compare the reading with other engine data while varying the engine speed.
Use live data to confirm that both sensors rise smoothly and consistently
Clean the throttle if it has carbon buildup
Run the relearn procedure with the scanner if the manufacturer requires it
Replace the part identified by the diagnosis

Good to know

Repair difficulty: medium
It can trigger limp mode.
It affects emissions.

What each character of P0221 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
2: Fuel injection
21: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0221?

Be careful: the car may suddenly lose power. If it goes into limp mode, get off the highway and calmly make your way to a repair shop.

What causes code P0221?

The most common causes are: worn track of sensor B (signal jumps); contact resistance at connector or wiring; throttle dirty or sticking.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.