P0124 is an OBD-II trouble code that points to a problem with your throttle position sensor (TPS) or its circuit. When this code sets, your engine computer is seeing a throttle signal that’s intermittent, unstable, or out of the expected range. You might notice hesitation, odd shifting, poor fuel economy, or a check engine light that keeps coming back. The good news is that P0124 is usually fixable with basic testing and reasonably priced parts. Understanding what this code means helps you avoid guesswork and unnecessary repairs.
What Does P0124 Mean?
P0124 stands for “Throttle/Pedal Position Sensor/Switch A Circuit Intermittent.” In simple terms, the ECU is getting a throttle position signal that cuts in and out, jumps around, or doesn’t match what it expects based on engine load and RPM.
Most modern vehicles use an electronic throttle body and one or more TPS sensors. The sensor converts throttle angle into a voltage signal. If that voltage is unstable or noisy for a certain amount of time, the ECU stores P0124 and turns on the check engine light.
Quick Reference
- Code: P0124
- Definition: Throttle/Pedal Position Sensor/Switch A Circuit Intermittent
- System: Engine management / throttle control
- Severity: Moderate – can affect drivability and safety
- Most common cause: Faulty TPS or wiring issue at the throttle body
Real-World Example / Field Notes
In the shop, P0124 often shows up on vehicles that have had a recent throttle body cleaning or intake work. A common pattern is a customer complaining of random surging at cruise, rough idle, and a check engine light that comes and goes. On scan data, I’ll see the throttle position percentage suddenly spike or drop while the pedal is steady. Wiggling the TPS connector or harness usually makes the signal glitch on the screen. Many times, the fix is as simple as repairing a loose connector pin or replacing a worn throttle position sensor assembly.
Symptoms of P0124
- Check engine light on: P0124 usually sets a steady MIL, sometimes accompanied by other throttle-related codes.
- Hesitation or stumble: You may feel a delay or stumble when you press the accelerator.
- Surging or unstable idle: Engine speed may hunt up and down at idle or while cruising.
- Poor throttle response: The vehicle may feel sluggish or respond unpredictably to pedal input.
- Transmission shift issues: On automatics, odd or harsh shifting can occur because the ECU uses throttle data for shift timing.
- Reduced power / limp mode: Some cars limit throttle opening to protect the engine and drivetrain.
- Increased fuel consumption: Incorrect throttle feedback can cause rich or lean conditions, hurting MPG.
Common Causes of P0124
Most Common Causes
- Faulty throttle position sensor (TPS): Internal wear, dead spots, or contamination inside the sensor cause an unstable voltage signal.
- Loose or corroded TPS connector: Poor contact at the plug can create intermittent signal drops or spikes.
- Damaged wiring near throttle body: Chafed, broken, or oil-soaked wires between the TPS and ECU cause intermittent circuits.
- Electronic throttle body wear: On drive-by-wire systems, a failing throttle body assembly can send erratic position feedback.
- Improper throttle body cleaning: Spraying cleaner into the sensor area or moving the throttle plate aggressively can damage the TPS.
Less Common Causes
- Bad accelerator pedal position sensor (APP): On some vehicles, mismatch between pedal and throttle signals can trigger P0124.
- Poor engine or chassis grounds: High resistance in ground circuits can make sensor voltages unstable.
- ECU (PCM) internal fault: Rare, but a failing driver or internal reference circuit can misread a good TPS signal.
- Aftermarket modifications: Low-quality throttle bodies, tuners, or wiring add-ons can introduce noise into the TPS circuit.
- Water intrusion: Moisture in the connector or harness from car washes, flooding, or coolant leaks can cause intermittent shorts.
Diagnosis: Step-by-Step Guide
To diagnose P0124 correctly, you’ll want at least a basic OBD-II scan tool that shows live data, a digital multimeter, and ideally a wiring diagram for your vehicle. A lab scope is helpful but not mandatory for most DIYers.
- Confirm the code and check for companions. Scan the vehicle and note all stored and pending codes. If you see other throttle or pedal codes (like P0121–P0123), diagnose them together since they share components.
- Check freeze frame data. Look at RPM, vehicle speed, throttle position, and load when P0124 set. This tells you if the issue happens at idle, cruise, or acceleration.
- Visual inspection of throttle body and wiring. With the engine off, inspect the throttle body, TPS connector, and harness. Look for broken insulation, rubbing, oil saturation, corrosion, or loose clips.
- Wiggle test with live data. Watch the TPS percentage or voltage on your scan tool while gently moving the harness and connector. Any sudden jumps or dropouts on the screen point to a wiring or connector issue.
- Check TPS reference and ground. With a multimeter, verify you have a stable 5V reference and a solid ground at the TPS connector (key on, engine off). A missing or low reference points upstream toward the ECU or harness.
- Measure TPS signal voltage. Back-probe the signal wire and slowly open the throttle (or press the pedal on some systems). The voltage should increase smoothly, typically from about 0.5V closed to around 4.5V wide open. Any sudden drop, flat spot, or noise indicates a bad sensor.
- Compare TPS and APP readings. On drive-by-wire systems, compare throttle position and accelerator pedal position on the scan tool. They should move in a coordinated, predictable way. Large mismatches may indicate a pedal sensor or throttle body issue.
- Check Mode $06 data (if available). Some scan tools can show detailed test results for the TPS circuit. Look for failed or marginal results for throttle position tests to confirm an intermittent problem.
- Clear codes and road test. After any repair or adjustment, clear the codes and perform a controlled test drive while monitoring live data to see if the signal remains stable.
Pro tip: If your scan data looks clean but the problem is intermittent, lightly tap the throttle body or wiggle the connector while watching the TPS signal. Many “mystery” P0124 cases show up only when vibration is introduced.
Possible Fixes & Repair Costs
Most repairs for P0124 are straightforward once you’ve identified the root cause. Common fixes include cleaning and tightening the TPS connector, repairing damaged wiring, or replacing the throttle position sensor or entire throttle body assembly. On some vehicles, a throttle relearn or ECU software update is required after parts replacement.
Typical repair costs vary widely by vehicle and shop rates. A simple connector cleaning or wiring repair might run $50–$150. Replacing a standalone TPS usually falls in the $100–$300 range parts and labor. An electronic throttle body assembly can cost $300–$800 or more, especially on newer or luxury models. Dealer-level diagnosis, reprogramming, and throttle relearn procedures can also add to the final bill.
Can I Still Drive With P0124?
You can usually drive short distances with P0124, but it’s not something you should ignore for long. Because the throttle signal is unstable, the engine may hesitate, surge, or suddenly lose power. On some vehicles, the ECU will enter a reduced power or “limp” mode, limiting throttle opening and speed. That can be dangerous if you need to accelerate quickly, merge, or pass. If drivability is severe or the vehicle goes into limp mode, avoid highway driving and have it checked as soon as possible.
What Happens If You Ignore P0124?
Ignoring P0124 can lead to worsening drivability, poor fuel economy, and potential safety issues when the throttle doesn’t respond as expected. Long term, running with an erratic throttle signal can cause extra stress on the transmission and catalytic converter due to inconsistent fueling and shifting. It also makes it easy to miss other new problems, since the check engine light will already be on.
Related Codes
- P0129 – Barometric Pressure Too Low
- P0127 – Intake Air Temperature Too High
- P0126 – Insufficient Coolant Temperature for Stable Operation
- P0125 – Insufficient Coolant Temperature for Closed Loop Fuel Control
- P0123 – Throttle/Pedal Position Sensor/Switch “A” Circuit High
- P0122 – Throttle/Pedal Position Sensor/Switch “A” Circuit Low
- P0121 – Throttle/Pedal Position Sensor/Switch “A” Circuit Range/Performance
- P0120 – Throttle/Pedal Position Sensor/Switch “A” Circuit
- P0119 – Engine Coolant Temperature Circuit Intermittent
- P0116 – Engine Coolant Temperature Circuit Range/Performance
Key Takeaways
- P0124 means the ECU sees an intermittent or unstable signal from the throttle position sensor “A” circuit.
- Common causes include a failing TPS, loose or corroded connectors, and damaged wiring near the throttle body.
- Symptoms range from a simple check engine light to hesitation, surging, and reduced power or limp mode.
- Proper diagnosis requires checking live data, wiring integrity, and TPS voltage sweep rather than guessing and replacing parts.
- Most repairs are manageable and typically cost between $100 and $800 depending on the parts and labor involved.
Vehicles Commonly Affected by P0124
P0124 is a generic OBD-II code, so you’ll see it on many makes and models. It’s especially common on high-mileage Ford and Chevrolet trucks and SUVs, Toyota and Lexus models with electronic throttle bodies, and various Hyundai, Kia, Nissan, and Honda vehicles. Compact cars, crossovers, and full-size pickups all use similar throttle control strategies, so the root causes and fixes are very similar across brands.
FAQ
Can P0124 clear itself?
P0124 can sometimes clear itself if the intermittent issue doesn’t reappear for several drive cycles. However, the underlying problem usually returns. If the light went off on its own, it’s still smart to scan for stored or pending codes and address any wiring or sensor issues before they get worse.
Is P0124 caused by a dirty throttle body?
A dirty throttle body can contribute to throttle issues, but P0124 is specifically about an intermittent electrical signal. Carbon buildup alone usually causes idle problems or P0505-type codes. That said, aggressive cleaning can damage the TPS or connector, so if the code appeared after cleaning, inspect the sensor and wiring closely.
Can a bad accelerator pedal sensor cause P0124?
Yes, on many drive-by-wire systems, the ECU constantly compares accelerator pedal position to throttle position. If the pedal sensor is glitchy or out of sync, it can trigger throttle-related codes including P0124. That’s why it’s important to check both TPS and APP data when diagnosing.
How do I know if I need a new throttle body or just a TPS?
It depends on your vehicle design and test results. If the TPS is separate and your voltage sweep test shows clear dead spots while wiring and grounds test good, you can usually replace just the sensor. If the TPS is integrated into the throttle body or the throttle plate is sticking, replacing the entire throttle body assembly is often the better long-term fix.
Can low battery voltage cause P0124?
Low system voltage can make sensor readings unstable and occasionally contribute to intermittent codes like P0124. If you’ve had starting issues, dim lights, or a recent battery change, test the battery and charging system. Fix any voltage problems first, then clear the codes and recheck before replacing sensors.