P0120 code: Throttle/Pedal Position Sensor A Circuit
P0120 means throttle/Pedal Position Sensor A Circuit. The code says where to look, not what failed — the fix depends on which cause your car actually has.
What P0120 means
The throttle position sensor (TPS) tells the computer how far the throttle is open so it can set fuel and, on drive-by-wire cars, control the throttle itself. P0120 is a general fault in the 'A' TPS circuit. Common causes are a failed sensor, a wiring or connector fault, or — on modern electronic throttle bodies where the sensor is built in — a failing throttle body. Because the computer relies on this for throttle control, a fault can drop the car into a reduced-power 'limp' mode.
P0120 symptoms
- Hesitation, surging, or poor throttle response
- Reduced-power or 'limp' mode
- Rough or unstable idle
- Stalling in some cases
- Check-engine light, sometimes with a warning light
What it costs to fix P0120
Typical range: $50–$500 · about ~0.3–1.5 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Throttle position sensor (standalone) | $20–$100 | ~0.3–0.8 hrs |
| Electronic throttle body (integrated TPS) | $150–$500 | ~0.5–1.5 hrs |
| Wiring / connector repair | $10–$120 | ~0.5–1.5 hrs |
Cheap on older cars with a bolt-on sensor; more on newer drive-by-wire cars where it means the throttle body. Wiring/connector repairs are inexpensive once located.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0120 for my exact vehicle →
How to fix P0120
Moderate — doable at home with common tools and patience
- Read the sensor's live data first
Because P0120 is the general circuit code rather than a specific high or low fault, start by watching TPS voltage on a scan tool at idle and through a slow throttle sweep. Whether the reading is dead, stuck, or glitching tells you which kind of fault you're hunting before you touch anything.
- Wiggle-test the harness while watching
With live data on screen, flex the wiring between the throttle body and the main harness and tap the connector. A jumpy reading during the wiggle test points to a connection fault — the cheap outcome — rather than the sensor element itself.
- Check power, ground, and connector at the sensor
Verify roughly 5 volts on the reference wire, a good ground, and clean, tight connector terminals. The sensor can only be as good as the circuit feeding it, and a missing reference or bad ground produces this code with a perfectly healthy sensor.
- Replace the TPS or throttle body
If the circuit checks out and the signal is still wrong, replace the sensor — a stand-alone part on older cable-throttle engines, the whole throttle body on drive-by-wire designs where the sensor is integrated. Follow with the relearn procedure your vehicle requires.
- Confirm the repair under real driving
Clear the code and drive with live data displayed, watching for a smooth signal through acceleration, cruise, and deceleration. An intermittent fault that survived the repair will show itself here rather than in the driveway.
DIY or shop? A home mechanic with a scan tool and multimeter can work this code methodically — the live-data and wiggle-test steps in particular cost nothing and frequently find the fault. The shop threshold is familiar for throttle codes: integrated drive-by-wire throttle bodies are pricier parts, relearns can require professional scan tools, and intermittent wiring faults that resist a wiggle test are time-consuming to trace. If the car is stuck in limp mode, weigh towing against limping it in gently.
Tools for the DIY steps: OBD2 scanner with live data · Digital multimeter · Screwdrivers and socket set · Electrical contact cleaner · Back-probe pins
Not sure which step applies to your car? Get the likely cause for your exact vehicle before buying anything for P0120.
Start a case with P0120 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 P0120?
Redline can’t determine from a symptom or code alone whether your car is safe to drive.
P0120: common questions
Can I drive with P0120?
Redline can't answer that from the code alone. It can cause hesitation or reduced-power mode, which is risky in traffic, so get it inspected promptly. If throttle response is unpredictable or power drops, don't drive it — have it towed.
Will P0120 cause limp mode?
It can. Because the computer depends on the throttle signal, a fault often triggers a reduced-power 'limp' mode as a safety fallback — the car runs but acceleration is limited until it's fixed.
Is the TPS part of the throttle body?
On most modern drive-by-wire vehicles, yes — so the repair may mean the whole electronic throttle body. Older cars often have a separate, cheaper bolt-on sensor.
How much does it cost to fix P0120?
Cheap on older cars with a standalone sensor; more on newer ones where it means a throttle body. Wiring fixes are inexpensive. Diagnosis tells you which applies before you buy parts.
Related trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P0120 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 P0120 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.