Fault code P2105 is called “Throttle Actuator Control (TAC) System – Forced Engine Shutdown Mode” 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 P2105
Fault code P2105 OBD-II is one possible code that indicates that the powertrain control module (PCM) has detected a fault. It therefore limits the operation of the throttle actuator control system.
The electronic control system uses data from several sensors to control, manage, and monitor the throttle position. The main sensors in these systems are usually the accelerator pedal position sensor and the throttle position sensor. These generate signal voltages that are used to activate the stepper motor in the throttle body.
An integrated throttle position sensor monitors the position of the throttle body. This information is used to correlate the pedal position to the actual throttle position. The PCM compares the actual throttle position to the desired or set throttle position given the current operating conditions.
Therefore, when the PCM detects any deviation in any involved component of the throttle control system. Which may affect the safe and reliable operation of the electronic throttle control system.
It will set code P2105 to force the throttle actuator control system to stop the engine.
Symptoms of vehicle malfunctions
The main signal that an error P2105 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.
It can also be warning signs such as:
- The “Check engine” control lamp on the control panel will light up (the code will be stored as a fault).
- Other related fault codes may also be present.
- Transition of vehicle operation to fail-safe or emergency mode.
- The engine cannot be accelerated, and throttle response is unresponsive.
- Automatic transmission does not shift.
- The engine is stalling or does not start well.
The P2105 code can range in severity from medium to severe, depending on the specific fault. Therefore, it is worth paying close attention to it.
Factors that can cause this error code
The error code P2105 can mean that one or more of the following problems have occurred:
- Open or short circuit in control circuit of throttle valve actuator or related systems.
- Defective throttle valve actuator due to mechanical wear of the actuator gears.
- Abnormally high or low voltage in the system.
- Failed pedal position sensor.
- Faulty throttle position sensor.
- Sometimes the cause is faulty PCM module.
How to fix or reset OBD-2 code P2105
Some suggested steps for troubleshooting and fix the error code P2105:
- Diagnose the code according to the manufacturer’s verification test to check the signal.
- Clear the error codes from the computer memory and test drive the vehicle to see if code P2105 appears again.
- Using the accelerator pedal, check the throttle position sensors and actuator operation.
- Inspect the accelerator pedal as well as the throttle valve for jamming in the open or partially open position.
- Check harness and connection, visually for problems, and correct if necessary.
- Test the actuator according to the manufacturer’s specified spot test.
- If no problem is found, check and, if necessary, replace the motor control module (PCM).
Diagnose and repair of problems
The first thing to do is to check the maintenance bulletins (TSB) for your particular vehicle. Your P2105 problem may be a known problem with a known fix issued by the manufacturer. This can save you time and money during diagnosis.
Next, locate the throttle actuator on your particular vehicle. This actuator is usually mounted at the front of the engine. On top of the engine, inside the wheel arches or against the bulkhead.
Wiring test
Once found, visually inspect the connector and wiring. Look for scratches, scuffs, exposed wires, burn spots, or melted plastic. Disconnect the connector and carefully inspect the terminals inside the connector.
See if they look burnt or have a green tint indicating corrosion. If you need to clean the terminals, use an electrical contact cleaner and a plastic-bristle brush. Allow to dry and apply electrical grease to the contact areas of the terminals.
If you have a diagnostic scan tool, clear the diagnostic trouble codes from memory and see if code P2105 returns. If it doesn’t, the problem is most likely related to the connection.
Test the actuator
If the P2105 code returns, we will need to test the actuator and associated circuits. There are usually 2 wires on each throttle actuator. First, disconnect the harness coming from the throttle actuator.
Using a digital multimeter, connect one lead of the meter to one terminal on the actuator. Connect the remaining meter lead to the other actuator terminal. It should not be open or shorted.
Check the resistance characteristics for your particular vehicle. If the actuator is shorted, the resistance will be infinite or nonexistent. If this is the case, replace the throttle actuator.
If this test is passed, use a multimeter to make sure you have 12 volts applied to the throttle actuator supply circuit. Red wire to the actuator supply circuit, black wire to ground.
Using a diagnostic tool that can activate the throttle actuator, turn on the actuator. If there is no 12 volts on the actuator, repair the wiring from the PCM or relay to the actuator. Also in this case, the PCM may be faulty.
If all is fine, make sure you have a good ground connection at the throttle actuator. Connect the test lamp to the plus end of the 12 V battery (red lead). And touch the other end of the test lamp to the ground circuit. The throttle valve actuator circuit goes to ground.
Using the diagnostic tool to actuate the throttle actuator. Check to see if the check lamp illuminates each time the diagnostic tool operates the throttle actuator.
If the indicator light does not come on, it indicates a faulty circuit. If it lights up, jiggle the wiring harness going to the actuator. To see if the check lamp blinks, indicating an intermittent connection.
If all the previous tests are passed and you keep getting error P2105. You most likely have a faulty throttle actuator. Although a failed PCM cannot be ruled out until the throttle actuator is replaced.
If you are unsure, seek the help of a qualified automotive diagnostician. The PCM must be programmed or calibrated for the specific vehicle in order to be installed correctly.
On which vehicles does this problem occur most frequently
Fault code P2105 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:
- Cadillac (CTS)
- Chevrolet (Aveo, Cobalt, Cruze, Traverse)
- Dodge
- Ford (Explorer)
- GMC
- Hyundai (Sonata, ix35)
- Jaguar
- Kia (Sorento, Sportage)
- Land Rover (Discovery, Range Rover)
- Lifan (X60)
- Opel
- Subaru
- Suzuki
- Toyota
- Volkswagen (Tiguan)
- GAZelle
- LADA (Vesta)
Fault code P2105 can sometimes be found with other errors. The most common are the following: P0017, P0122, P0222, P0303, P0336, P0605, P0660, P0661, P2104, P2106, P2107, U0151.