ezOBD2 - Free OBD2 Code Lookup and Check Engine Light Diagnostic Tool

Diagnose Your Check Engine Light

Enter OBDII code below:

Code P0121

Symptoms

• Check Engine Light is on

• Poor engine performance

• Hesitation or stalling

Common Causes

• Faulty Throttle Position Sensor

• Wiring issues (short or open circuit)

• Faulty PCM

Glossary

PCM: Powertrain Control Module

TPS: Throttle Position Sensor

Related Codes

• P0120

• P0122

• P0123

Official description

Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance

Laymans terms

This code means that the car's computer is getting confusing signals from the sensor that tells it how much you're pressing the gas pedal. It's like if your game controller was sending mixed signals to your console.

Explanation

The P0121 code is triggered when the Powertrain Control Module (PCM) detects that the Throttle Position Sensor (TPS) is not operating within the expected range, or it is not performing as expected.

Technical description

The Throttle Position Sensor (TPS) is a sensor used to monitor the position of the throttle in an internal combustion engine. It consists of a variable resistor that changes its resistance as the throttle moves. The PCM uses this information to determine engine load and adjust fuel delivery and ignition timing. A P0121 code indicates that the TPS signal is out of the predetermined range or is inconsistent with the expected values.

Diagnosis steps

• Use an OBD-II scanner to confirm the code

• Inspect the wiring and connections to the TPS

• Test the TPS with a multimeter

Repair procedures

• Replace the Throttle Position Sensor

• Repair or replace damaged wiring

• Reprogram or replace the PCM if necessary

Tools required

• OBD-II scanner

• Multimeter

• Screwdriver set

Estimated repair cost

$100 - $300

Difficulty level

Moderate

Commonly affected vehicles

• Ford F-150

• Chevrolet Silverado

• Toyota Camry

Preventive measures

• Regularly inspect and clean the throttle body

• Ensure proper maintenance of electrical connections

• Use quality fuel to prevent sensor contamination

Error code type

Sensor Issue

User experience recommendations

• Do not ignore the Check Engine Light

• Have the vehicle inspected by a professional

• Avoid driving at high speeds until the issue is fixed

Warranty information

Check with your vehicle manufacturer for specific warranty coverage on emission-related components.

Historical data

The P0121 code has been common since the introduction of electronic throttle control systems in vehicles, which began in the late 1990s.

Urgency level

Moderate – While the vehicle may still be drivable, it can lead to poor performance and increased fuel consumption.

Legal and safety notice

Driving with an unresolved P0121 code can lead to increased emissions, which may not comply with local environmental regulations.

Testing conditions

• Engine at operating temperature

• Throttle pedal pressed

Component location

The Throttle Position Sensor is typically located on the throttle body, which is attached to the intake manifold.

FAQs

Q: Can I drive my car with a P0121 code?
A: You can drive your car, but it's not recommended as it may lead to poor performance and increased fuel consumption.

Q: How do I reset the P0121 code?
A: You can reset the code using an OBD-II scanner, but it's important to fix the underlying issue first.

Last updated: Jan 16, 2026 • Source: internal database
🌙