Throttle Control Circuits dictate the amount of opening for your throttle body in relation to your accelerator pedal. These circuits control the stepper motor that’s part of your throttle body. When you depress your gas pedal, the throttle opens, allowing more air into your engine. When there’s a problem with the circuit or the wiring, the P0121 trouble code can trigger.
There are many different types of throttle circuits, depending on the year of your vehicle. If you happen to own an electronic throttle, this is included in the throttle body. This means that you may require a replacement unit. If you have a traditional wire throttle unit, the throttle position sensor or Powertrain Control Module may have gone bad.
Use a proper OBDII scan tool to pull the stored MIL check engine light trouble code.
What Does P0121 Code Mean?
This OBDII trouble code is defined as Throttle or Pedal Position Sensor/Switch “A” Circuit Range Problem. What this error code means is that the voltage that your ECU / PCM expects is either too high or too low. When this problem is encountered, your MIL status will trigger and your check engine light will turn on.
What Does This Code Mean?
When you encounter the stored P0121 trouble code, this means that there’s a problem with your throttle signal. The Throttle Position Sensor is usually mounted in the throttle body. If you happen to own a later model vehicle, the Pedal Position Sensor is part of the Accelerator Pedal assembly.
Recently had your vehicle serviced? If so you may need to reprogram your throttle or accelerator pedal assembly to reset the throttle signal. Failing that you may need to test the accelerator pedal to see if there’s a problem.
The Throttle Position Sensor reads the input from your foot in terms of how much throttle is needed. This will increase the amount of air entering the engine, and allows the PowerTrain Control Module or PCM to increase fuel.
P0121 Symptoms
- Abnormal throttle response
- Uncontrollable throttle or idle
- Engine may be hard to start
- Hesitatation during acceleration
Fixing P0121 issues
- How To Test a Ford Fusion Throttle Body
- DTC P0121 – How To Change a WRX Throttle Body
- DTC P0123 – How To Change a LS1 Throttle Body
- DTC P0507 – How To Replace a VQ35 Throttle Body
Related P0121 OBDII Codes
P0120 Throttle/Pedal Position Sensor/Switch “A” Circuit
P0121 Throttle/Pedal Position Sensor/Switch “A” Circuit
P0122 Throttle/Pedal Position Sensor/Switch “A” Circuit Low
P0123 Throttle/Pedal Position Sensor/Switch “A” Circuit High
P0124 Throttle/Pedal Position Sensor/Switch “A” Circuit Intermittent
Common Problems That Trigger the P0121 Code
- Defective TPS or Switch
- Contaminated or dirty throttle body
- Faulty or corroded Throttle/Pedal Position Sensor
- Bad wiring from your Throttle sensor to your ECU
How to Troubleshoot throttle issues
Using an OBDII scan tool, read the real-time data from your throttle sensor. With the key set to the ON position, read the data to see if there’s a 5-volt range. There should always be a steady reference voltage that maxes out at 5 volts.
