When a throttle sensor fails on a modern car, the engine often drops into reduced power and will barely accelerate. A P0220 code means the engine computer found a problem in the circuit for throttle or pedal position sensor B.
This guide explains what sensor B does, why the car limits power and how to test the circuit step by step.
P0220 Code Breakdown
Every OBD-II code follows the same five-character pattern set by the SAE J2012 standard. Each character narrows down which system has the fault. This table shows what each part of the code tells you.
| Character | Meaning | What It Tells You |
|---|---|---|
| P | Powertrain | The fault is in the engine or transmission systems. |
| 0 | Generic (SAE) code | The definition is the same on every OBD-II vehicle. |
| 2 | Fuel and air metering | The fault involves fuel and air metering, such as injectors, the fuel pump, throttle sensors or boost control. |
| 20 | Specific fault | Throttle/Pedal Position Sensor/Switch B Circuit Malfunction |
What the P0220 Code Means
The SAE J2012 standard defines the P0220 code as Throttle/Pedal Position Sensor/Switch B Circuit Malfunction. On most vehicles with electronic throttle control, sensor B is the second throttle position sensor built into the throttle body. The throttle body has two sensors that both read the throttle plate angle, so the PCM can compare them.
Most of these sensors get a 5-volt reference and a ground from the powertrain control module (PCM) and send back a signal between about 0.5 and 4.5 volts. On many designs, one sensor’s voltage rises as the throttle opens while the other falls, or the two rise at different rates.
Because the throttle is drive-by-wire, the PCM cannot let a bad signal open the throttle by mistake. When a sensor fails, it usually limits throttle opening and puts the car into reduced power or limp mode.
This is the general circuit code for the throttle position sensor B. The PCM saw a signal it could not accept, such as one that is missing, out of range or does not match a related input, but the code does not say whether the signal was too low or too high.
Symptoms of a Sensor B Fault
Because the throttle is electronic, symptoms are often obvious. Common signs of a P0220 code include:
- Check engine light and often a wrench or traction light
- Reduced power or limp mode
- Little or no response to the gas pedal
- High or unstable idle
- Stalling or hesitation
- Harsh or delayed shifting on some automatics
Many cars recover after the engine is restarted, then fall back into reduced power when the fault returns. That pattern points to a wiring or connector problem rather than a fully dead sensor.
What Causes the P0220 Code?
A general circuit fault can come from anywhere in the circuit. These are the usual causes:
- Loose or corroded connector. Moisture and heat attack the pins.
- Damaged wiring. Wires can chafe, break or melt near hot or moving parts.
- Failed throttle position sensor B. Internal wear or damage stops it from reporting correctly.
- Problem with the 5-volt reference or ground. Shared circuits can affect several sensors at once.
- PCM fault. Rare.
Tools You Will Need
You can do most of this testing at home with basic tools:
- OBD-II scan tool that shows both throttle sensors
- Digital multimeter with back-probe pins
- Wiring diagram for your vehicle
- Throttle body cleaner
- Scan tool or procedure for throttle relearn
Step-By-Step Diagnosis of the P0220 Code
Work from the scan tool to the connector, and check for related throttle codes before you replace anything.
Check Live Data
With the key on and engine off, look at both throttle position sensor values and voltages. Press the pedal slowly through its full travel. Note the closed and wide-open readings for sensor B. A reading stuck near 0 or 5 volts confirms a circuit fault.
Inspect the Connector and Wiring
Find the throttle position sensor B and check that the connector is fully seated and locked. Look for corrosion, bent pins and wiring that rubs on brackets or hot parts.
Test Reference, Ground and Signal
Back-probe the connector with the key on. The reference should read close to 5 volts, the ground close to 0 volts, and the signal should match the value your service manual lists. Any wire that fails tells you where to look next.
Check for Related Codes
Codes such as P2135 (sensor correlation) or P2101 (throttle motor) often set alongside this one. Fixing a shared reference or ground can clear several throttle codes at once.
How to Fix the P0220 Code
Match the repair to what your tests found. Then clear the code and drive under the same conditions that set it.
- Clean or replace the connector if pins are corroded or loose. Add dielectric grease to the seal.
- Repair damaged wiring between the throttle body and the PCM.
- Clean a dirty throttle body if carbon is stopping the plate from moving freely.
- Replace the throttle body or sensor if sensor {L} fails tests. On most drive-by-wire cars, the sensors are part of the throttle body.
- Run a throttle relearn after cleaning or replacing the throttle body.
Many vehicles need a throttle relearn after a battery disconnect or throttle body replacement. Without it, the idle may be high or unstable. Follow the service manual procedure, which may only need a key-on wait or may need a scan tool.
Common Mistakes to Avoid
These mistakes waste money or leave the real fault in place:
- Replacing the sensor before checking the connector and wiring
- Ignoring other codes that share the same reference or ground
- Skipping the throttle relearn after replacement
- Buying a cheap throttle body with sensors that do not match the factory output
What Repairs Cost
The cost to fix a P0220 code depends on the cause. This table shows typical ranges for parts and labor.
| Repair | DIY Cost | Typical Shop Cost |
|---|---|---|
| Connector cleaning or pigtail | $10 to $40 | $75 to $200 |
| Wiring repair | $10 to $30 | $100 to $300 |
| Throttle body cleaning | $10 | $75 to $150 |
| Throttle body with sensors | $100 to $400 | $300 to $700 |
| Accelerator pedal assembly | $60 to $250 | $200 to $450 |
Most of the cost comes from the throttle body itself. Testing the connector and wiring first can save the price of a part you may not need, since many of these faults are corroded pins.
Is It Safe to Drive with a P0220 Code?
It is risky. Many cars drop into reduced power with this code, which makes merging, passing and climbing hills dangerous.
Drive only as far as needed to reach a repair shop, and avoid highways if the car will not accelerate normally. If the throttle does not respond at all, have it towed.
Related Codes
These codes often show up with this one or point to the same system:
| Code | Meaning |
|---|---|
| P0221 | Throttle/Pedal Position Sensor/Switch B Circuit Range/Performance Problem |
| P0222 | Throttle/Pedal Position Sensor/Switch B Circuit Low Input |
| P0223 | Throttle/Pedal Position Sensor/Switch B Circuit High Input |
| P0224 | Throttle/Pedal Position Sensor/Switch B Circuit Intermittent |
| P2135 | Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation |
| P0120 | Throttle/Pedal Position Sensor/Switch A Circuit Malfunction |
Fixing Throttle Position Sensor B
A P0220 code means the PCM found a fault in the throttle or pedal position sensor B circuit. Connectors, wiring and worn sensors cause most cases.
- Check both sensors in live data.
- Inspect the connector and wiring.
- Test reference, ground and signal.
- Run a throttle relearn after any repair.
Frequently Asked Questions
Why Does the P0220 Code Put My Car in Limp Mode?
With electronic throttle control, the PCM must be certain where the throttle is. When it cannot trust sensor B, it limits throttle opening so the car cannot accelerate on its own. Reduced power is a safety feature, not a separate fault.
Can I Replace Just the Sensor?
On most drive-by-wire vehicles, the throttle position sensors are built into the throttle body and cannot be replaced separately. Some older vehicles and some pedal assemblies have separate sensors. Check a parts catalog for your vehicle.
Do I Need a Throttle Relearn?
Often, yes. After a throttle body replacement, cleaning or battery disconnect, many vehicles need to relearn the closed throttle position. Some do it on their own after a key-on wait, while others need a scan tool.
What Does Reduced Power Mode Feel Like?
The engine starts and idles, but the throttle opens only a little no matter how far you press the pedal. The car may struggle to reach highway speed, and a warning such as a wrench light or reduced engine power message often appears. Restarting may clear it for a while.
Can Water Get into the Throttle Body Connector?
Yes. Engine washing, heavy rain and a worn connector seal can let water in. Water causes signal errors that come and go. Dry the connector, clean the pins and replace the seal or pigtail if it is damaged.