P2105 trouble code definition
Throttle Actuator Control System (TAC) - Forced Engine Shutdown
What the P2105 code means
This code is set when the PCM (Powertrain Control Module) has failed or the PCM has detected one or more problems that could result in a safety issue from incorrect throttle control. The throttle actuator on modern vehicles is electrically controlled. There isn’t a direct connection between the throttle pedal at your foot and the throttle valve.
It is possible the PCM could open the throttle valve and cause the vehicle to accelerate dangerously against the driver's commands. For this reason, the PCM follows some very strict guidelines to insure the system is operating correctly. If these guidelines are not met, the PCM places the car in a default forced engine shutdown mode for safety reasons.
What causes the P2105 code?
This code is set when the correlation between the throttle pedal and the throttle valve don’t match. The PCM determines this by monitoring the resistance and or voltage of sensors mounted on the throttle pedal and the throttle valve. If the position of these two sensors don’t match, the vehicle is put into a safe mode that will either turn the motor off or only allow it to idle. This depends on the programming the manufacturer chooses to use.
The data from other systems is used when calculating throttle position. If any of these systems has problems, the PCM’s throttle position calculations can be compromised, therefore putting the vehicle in this default safety mode and setting this code.
What are the symptoms of the P2105 code?
- The vehicle will die and will not start
- The Check Engine Light will be on
- The car will idle but won’t go
How does a mechanic diagnose the P2105 code?
This system is fairly simple in its design, but because of the programming involved, it can be difficult to diagnose. The first step is to connect a scanner and look for any data that looks incorrect. This could be a crank sensor, camshaft sensor, TPS at the throttle valve, throttle pedal sensor at the throttle pedal, PCM, wiring harness problem, MAF (Mass Airflow Sensor), MAP (Manifold Absolute Pressure) sensor and several other possibilities.
It’s important the technician has a firm understanding of each of these systems to enable him or her to recognize problems that can affect the TAC system. For this reason, most other DTC’s (Diagnostic Trouble Codes) should be diagnosed first as they could contribute the the malfunction of the TAC system and set this code.
Common mistakes when diagnosing the P2105 code
Due to the amount of systems that can affect the TAC system, it is excessively easy to miss something going on with other systems that will affect the TAC system. It’s important to understand this code is set when the vehicle enters a default mode for safety reasons.
Anytime a fault is present that can affect the throttle control, the vehicle enters into a safe mode to insure the vehicle doesn’t accelerate out of control.
How serious is the P2105 code?
The code itself isn’t serious. It merely states that the vehicle has been put into a default safety mode. Although the code exists for the safety of the occupants and therefore suggests there is the possibility the vehicle could become out of control if it isn’t placed in this safety mode.
What repairs can fix the P2105 code?
- Repairing faulty or damaged wiring
- Replacing the throttle body and or the TPS
- Replacing the throttle pedal assembly and or throttle pedal sensor
- Replacing the PCM
- Replacing the ignition coils
- Fixing an EGR system failure
Additional comments for consideration regarding the P2105 code
When this code is set depends greatly on the programming choices of the manufacturer. Since modern vehicle computer systems utilize the PCM to control almost every function, it is very common that other systems outside the TAC (Throttle Actuator Control) system will affect the PCM’s control of the TAC system. In the interest of safety and the risk of an out of control vehicle due to sudden uncontrolled acceleration, manufacturer’s default the engine to shut down for obvious safety reasons.
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