P0120 on Chevrolet: How to Diagnose & Fix
Throttle/Pedal Position Sensor Circuit Malfunction
1 Chevrolet model · 1 documented issue · 1 critical · $120-$450 repair
P0120 on Chevrolet by model: symptoms, diagnosis and fix
Tahoes with drive-by-wire throttle (APP pedal sensor + TAC module + electronic throttle body) commonly trigger a 'Reduced Engine Power' message and drop into limp mode with severely limited acceleration - a safety concern in traffic. On GMT800s the frequent culprits are a broken/chafed wire in the throttle-body harness (often the yellow wire), corroded engine grounds, or a dirty/sticking throttle body (P1516/P1515). GMT900s see similar throttle-actuator/APP faults (P2101/P2135/P0120 family).
Common Symptoms
- 'Reduced Engine Power' warning message
- Limp mode / severe loss of acceleration
- Hesitation or surging
- Check Engine light with throttle codes
- Intermittent power loss that clears on restart
How to Fix
Retrieve codes to isolate the branch: P1515/P1516 point at the TAC/throttle actuator, P2135/P0120-series at the TPS/APP correlation. Start with the cheap, common causes: clean the electronic throttle body, inspect and repair the throttle-body wiring harness (especially chafed/broken wires) and clean/tighten engine grounds. If the throttle body's internal TPS is faulty, replace the electronic throttle body assembly (ACDelco units available; part roughly $120-300). A failed APP pedal sensor is a less common cause.
Sources for this issue (1)
P0120 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0120 mean on a Chevrolet?
P0120 stands for "Throttle/Pedal Position Sensor Circuit Malfunction." This code indicates a malfunction in the throttle position or accelerator pedal position sensor circuit. These sensors tell the computer how far the throttle plate is open or how far you've pressed the pedal, which the computer uses to control engine power and, on drive-by-wire systems, the throttle itself. When the signal is out of range, erratic, or doesn't make sense relative to other inputs, P0120 sets. Symptoms can include hesitation, surging, stalling, or the vehicle entering a reduced-power 'limp' mode for safety. On Chevrolet it is documented across 1 model: Tahoe.
What are the most common causes of P0120?
The most common causes of P0120 are: Failed throttle position sensor, Corroded or loose TPS/pedal sensor connector, Damaged or shorted sensor wiring, Carbon buildup or a sticking throttle body, Worn throttle body or throttle plate, Poor sensor reference voltage or ground, Faulty accelerator pedal position sensor, Faulty PCM/ECM (rare). The specific cause varies by vehicle.
How much does it cost to fix P0120 on a Chevrolet?
Published repair estimates on Chevrolet range from $120 to $450 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0120 on a different make?
View P0120 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.