📟
P0120 directly affects throttle response and can stall your engine. Before replacing the TPS sensor, clean the throttle body first - carbon buildup is a frequent culprit. Check wiring at the TPS connector for corrosion or damage before condemning the sensor. See top-rated scanners on Amazon ↗
🗺️ Where Is the Problem?
Blueprint view - P0120 fault localized to throttle body / TPS sensor at intake
These are statistical causes across ALL vehicles - your exact car may rank differently
For example, on a Honda 4-cyl the downstream O2 sensor causes P0120 64% of the time, but on a GM 5.3L V8 the catalytic converter is the cause 71% of the time. Get a probability ranking built specifically for your year, make, model, and mileage.
🔎 Get the ranking for my exact car - $5.99 →
🎯 Top Causes & Probability
55%
#1 - Most Likely
Failed TPS Sensor
The throttle position sensor itself has failed internally. The sensor's resistive track wears out over time, producing an out-of-range or missing voltage signal to the PCM. This is the most common cause and often requires sensor replacement. OEM or quality aftermarket sensors are recommended.
🔩 Part
$30–$120
👨🔧 Labor
$40–$100
⚡ DIY Difficulty
Easy
25%
#2 - Check First
Dirty or Carbon-Fouled Throttle Body Affecting TPS
Heavy carbon buildup on the throttle plate or bore can prevent the throttle from returning to its closed position accurately, causing the TPS to read incorrectly. A thorough throttle body cleaning with throttle body cleaner often resolves this without any parts replacement.
🔩 Part
$5–$15
👨🔧 Labor
$0–$60
⚡ DIY Difficulty
Easy
12%
#3 - Less Common
Wiring Fault in TPS Circuit
Damaged, corroded, or chafed wiring in the TPS signal, reference voltage, or ground circuits can trigger P0120. Inspect the wiring harness from the TPS connector back to the PCM for any signs of heat damage, rodent chewing, or broken wires at flex points.
🔩 Part
$5–$40
👨🔧 Labor
$60–$150
⚡ DIY Difficulty
Medium
8%
#4 -
PCM Fault
In rare cases, the PCM's TPS input circuit fails internally, misreading a valid signal as out of range. This is a diagnosis of exclusion - confirm only after verifying the sensor and all wiring are good. PCM replacement or reprogramming is expensive and should be a last resort.
🔩 Part
$200–$800
👨🔧 Labor
$100–$200
⚡ DIY Difficulty
Hard
🚗 Most Affected Vehicles
🔧 Step-by-Step Diagnosis
- Clean the Throttle Body First - Remove the air intake hose and spray throttle body cleaner on the plate and bore. Manually open the throttle while cleaning. Clear codes and test drive. Many P0120s resolve after a thorough cleaning.
- Check TPS Voltage at Idle and WOT - With a multimeter or scan tool, verify the TPS signal voltage is approximately 0.5V at closed throttle and rises smoothly to ~4.5V at wide-open throttle. Erratic or flat readings confirm a failed sensor.
📍 Find a Trusted Shop Near You
Please enter a valid 5-digit ZIP code.
Tips for Choosing a Shop
- Ask if they charge a diagnostic fee and whether it applies toward the repair
- Request a written estimate before approving any work
- Ask specifically about the part brand - OEM vs. aftermarket matters for this code
- Check Google reviews for recent mentions of the specific repair you need