A car that drops into reduced power for a moment and then recovers often has a loose connection. A P0229 code means the engine computer caught the throttle or pedal position sensor C signal dropping out or jumping.
This guide explains how intermittent faults set, what causes them and how to catch one while it happens.
P0229 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. |
| 29 | Specific fault | Throttle/Pedal Position Sensor/Switch C Circuit Intermittent |
What the P0229 Code Means
The SAE J2012 standard defines the P0229 code as Throttle/Pedal Position Sensor/Switch C Circuit Intermittent. Sensor C is less common than sensor A or B. On some vehicles it is a third throttle or pedal position sensor, and on others it is an accelerator pedal sensor or an idle or wide-open throttle switch. Check your service manual to see what it is on your vehicle.
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.
Intermittent means the throttle position sensor C signal dropped out or jumped for short moments, faster than the real condition could change. The fault may last only a fraction of a second, so the circuit often tests fine when parked.
Signs of an Intermittent Sensor C Signal
Because the throttle is electronic, symptoms are often obvious. Common signs of a P0229 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.
Common Causes of the P0229 Code
Anything that breaks the circuit for an instant can set this code:
- Loose connector. A connector that is not fully locked loses contact with engine movement.
- Spread or corroded terminals. Weak pins lose grip as they heat up.
- Chafed wiring. Insulation wears through where wires rub on brackets.
- Broken wire inside the insulation. The copper separates only when flexed.
- Failing throttle position sensor C. Internal faults can come and go with heat.
- Moisture in the connector. A worn seal lets water in during rain or washing.
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
How to Diagnose the P0229 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 C. A reading stuck near 0 or 5 volts confirms a circuit fault.
Graph the Signal and Wiggle the Wiring
Graph the throttle position sensor C signal with the engine running. Gently wiggle the connector, then the wiring one section at a time. A sudden spike or drop marks the bad spot. Tap the sensor body lightly too.
Inspect the Connector
Turn the engine off and unplug the connector. Look for corrosion, spread pins, a broken lock and water inside. Check the engine ground straps if several sensors glitch at the same time.
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.
Repairs That Fix the P0229 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 parts when the circuit tests fine at rest
- Not graphing the signal while wiggling the wiring
- Skipping the throttle relearn after replacement
- Buying a cheap throttle body with sensors that do not match the factory output
Repair Cost Breakdown
The cost to fix a P0229 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.
Can You Drive with a P0229 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 |
|---|---|
| P0225 | Throttle/Pedal Position Sensor/Switch C Circuit Malfunction |
| P0226 | Throttle/Pedal Position Sensor/Switch C Circuit Range/Performance Problem |
| P0227 | Throttle/Pedal Position Sensor/Switch C Circuit Low Input |
| P0228 | Throttle/Pedal Position Sensor/Switch C Circuit High Input |
| P2135 | Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation |
| P0120 | Throttle/Pedal Position Sensor/Switch A Circuit Malfunction |
Fixing Throttle Position Sensor C
A P0229 code means the sensor C signal drops out or jumps for short moments. Loose connectors and chafed wiring cause most cases.
- Use freeze frame data to recreate the fault.
- Graph the signal while you wiggle the wiring.
- Inspect the connector for spread pins and water.
- Replace the sensor if it glitches when tapped.
Frequently Asked Questions
Why Does the P0229 Code Come and Go?
Intermittent faults often appear only with heat, vibration or moisture, and only for a split second. Parked in the driveway, everything may test fine. Graphing the signal while wiggling the wiring is the best way to catch it.
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.