Fault code P2121 is called “Throttle/Pedal Position Sensor/Switch (TPS) “D” Circuit Range/Performance Problem” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.
Technical description and explained code P2121
This Diagnostic Trouble Code (DTC) is a generic powertrain code. Error P2121 is considered a general code because it applies to all makes and models of vehicles. Although the specific repair steps may vary slightly from model to model.
The throttle position sensor (TPS) reacts to the movement of the accelerator pedal. It is a type of potentiometer. It converts the throttle position into a voltage output and sends a voltage signal to the engine control module (ECM). It also determines the opening and closing speed of the throttle and provides a voltage signal to the ECM.
Code P2121 means that the vehicle’s computer has detected a TPS (Throttle Position Sensor “D”) voltage outside the normal operating range. When the throttle is closed, the signal is about 0.45 volts, and the lower limit when open is 0.17 to 0.20 volts.
Simply put, the throttle position sensor is used to determine what position the throttle is in. If the signal value is very different from the reference, this code is set.
Symptoms of vehicle malfunctions
The main signal that an error P2121 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.
It can also be warning signs such as:
- Check engine light on the control panel will illuminate.
- Ignition jerking/missing at idle or under load.
- Engine stalls or starts poorly.
- The engine cannot be accelerated, throttle response is unresponsive.
- Bad acceleration.
- Engine power drop due to slow throttle response.
- Black smoke from exhaust pipe.
Fault P2121 is not considered serious, however engine operation will be disturbed, also acceleration problems may occur. It is recommended to eliminate this fault as soon as possible to avoid further aggravation of the problem.
Factors that can cause this error code
The error code P2121 can mean that one or more of the following problems have occurred:
- Throttle position sensor circuit is open or bad electrical connection.
- Throttle position sensor wiring harness is open or shorted to ground or other wire.
- Corrosion on MAP or TPS connector.
- Throttle position sensor is defective.
- Problem with engine control module (PCM).
How to fix or reset OBD-2 code P2121
Some suggested steps for troubleshooting and fix the error code P2121:
- Read all stored data and error codes with an OBD-II scan tool. To find out when and under what circumstances the error occurred.
- Clear the error codes from the computer memory and test-drive the vehicle to find out if the malfunction appears again.
- Visually inspect the electrical wiring and connections related to the throttle “D” position sensor for looseness and damage.
- Compare “A” and “D” throttle position sensors using a scan tool, and replace faulty sensor if necessary.
- Clear error code from computer memory again, test drive vehicle to see if problem is resolved.
Diagnose and repair of problems
Carefully check the throttle position sensor (TPS), wiring connector, and wiring itself for breaks, etc. Repair or replace if necessary to clear error P2121.
Check the voltage at the TPS, it should be between 0.45-0.17 volts (some vehicles may have different values). If the voltage is too low or too high, this indicates a problem. Replace the sensor if necessary.
If recently replaced, you may need to adjust the TPS. On some vehicles, the installation instructions require a proper adjustment (see repair manual for details).
If there are no symptoms, the problem may be intermittent, and clearing the code may temporarily resolve it. If this is the case, you should definitely check the wiring to make sure it is not rubbing or frayed anywhere, etc.
On which vehicles does this problem occur most frequently
Fault code P2121 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:
- Chevrolet (Captiva)
- Ford (Focus, Mondeo, S-Max)
- Lexus (GS300, IS300)
- Opel (Corsa)
- Pontiac (Vibe)
- Porsche (Cayenne)
- Toyota (Alphard, Camry, Corolla, Ipsum, Land Cruiser, RAV4)
Fault code P2121 can sometimes be found with other errors. The most common are the following: P0571, P2120, P2122, P2123, P2124, P2138, P1260, U1900.