P2104 Code: Throttle Actuator Control System一Forced Idle

The electronic throttle control (ETC) system electrically opens the throttle valve. It usually consists of accelerator pedal position (APP) sensors, an electronic throttle actuator, throttle position (TP) sensors, and an electronic control unit.

Once the powertrain control module (PCM) detects a problem with the ETC system, a P2104 code will be logged by on-board diagnostics.

What Does the P2104 Code Mean?

Diagnostic trouble code (DTC) P2104 stands for “Throttle Actuator Control System一Forced Idle.”

As the driver steps on the accelerator pedal, the APP sensors send a signal to the PCM and let it know how much power is being requested from the driver. This allows the ETC system to open or close the throttle valve.

If the PCM detects an abnormal signal from any of the ETC system’s components, the computer will set code P2104. This code can also be triggered when the throttle is not opening in proportion to the signal received from the APP sensors.

Once the code is set, the vehicle’s fail-safe or limp home mode will kick in, limiting the available power from the engine to prevent unwanted acceleration. This mode usually causes limited engine speed (about 1200 to 1600 RPMs), little to no accelerator pedal response, and a disabled cruise control system.

If you’re planning to diagnose or fix P2104 yourself, you can learn more in our technical discussion about electronic throttle body system sensors.

Note: The definition of code P2104 may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of the P2104 Code?

• Faulty electronic throttle body
• APP sensor assembly failure
• Throttle position sensor failure
• Circuit issues, such as damaged wires or a poor connection
• Issues with the PCM, such as software in need of an update

What are the Common Symptoms of the P2104 Code?

• Decreased engine performance
• Illuminated check engine light
• Illuminated ABS light
• Shifting problems
• Little to no throttle response

How to Diagnose the P2104 Code

P2104 is a generic DTC that applies to OBD-II equipped vehicles. However, keep in mind that steps for diagnosis and repair may vary from one vehicle to another.

It’s a good idea to bring your vehicle to a licensed mechanic to ensure that the right diagnostic steps are followed. But if you’re a seasoned DIYer who has enough knowledge on diagnosing engine codes, then you may go ahead and do it yourself.

To help you out, here is a video that shows what the process might involve:

How to Fix the P2104 Code

Fixing a P2104 code can be confusing and frustrating if you don’t have the right tools and know-how. If you plan to diagnose and repair the problem yourself, make sure you’re equipped with the appropriate repair manual or online repair database. Both are excellent sources of vehicle-specific repair information, so you might want to check those out.

About Electronic Throttle Body System Sensors 

Electronic throttle body systems have redundant sensors on the accelerator pedal and redundant throttle position sensors on the throttle body for feedback purposes. The motor that drives the throttle plate doesn’t just open the throttle, it closes it as well.

If the ECM/PCM detects any mismatch in the redundant signals from any of the potentiometers (accelerator pedal sensors or throttle position sensors), throttle control will be lost and the engine will only idle, but most platforms won’t store code P2104. Since 1994, Power Stroke diesels have been programmed to lose throttle response and idle if the idle validation switch and the TP sensor on the accelerator pedal assembly disagree.

On a gas burner, if an intake manifold vacuum leak causes an elevated idle concern, the ECM/PCM will close the throttle plate, and if the idle remains elevated, the ECM/PCM will, on some platforms, de-energize the injectors.

It’s all about protecting the driver and passengers from disaster.