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P2104 OBD-II Trouble Code: Throttle Actuator Control System Forced Idle

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P2104 trouble code definition

Throttle Actuator Control System Forced Idle

What the P2104 code means

P2104 is an OBD-II generic code for the engine control module (ECM) detecting a major failure in the throttle actuator control (TAC) system causing the ECM to go into failure mode forced idle and limiting the engine to an idle RPM limit only. The throttle will not respond to any increase in throttle.

What causes the P2104 code?

  • The engine control module is in failure management mode from a major failure in the throttle actuator control system and sets code P2104 for limiting the engine to idle closed throttle only.

  • The throttle actuator control system failure is the cause and will may have set other failure codes or the throttle was held partly open during starting the vehicle and the ECM detected the throttle open.

What are the symptoms of the P2104 code?

  • The Check Engine Light will be illuminated and the code is set in ECM memory as a fault along with the failure code that caused the ECU to go into failure mode if there is another failure.

  • The engine will have no acceleration and no throttle response and the engine will idle only.

  • The symptoms encountered will depend on the problem that caused the failure mode.

How does a mechanic diagnose the P2104 code?

  • Scans and documents the code in the ECM to check the freeze frame data for failure

  • Diagnoses all codes as per the manufacturer's pinpoint tests

  • Diagnoses and repairs codes other than P2104 first, there may be codes to other systems that caused the failure mode to be activated within the ECM

  • Checks the throttle and pedal for being held open mechanically

  • Scans and looks at the throttle position sensors PID’s for proper throttle position and operation

Common mistakes when diagnosing the P2104 code

  • Clearing ECM memory codes before checking the freeze frame data for the main failure problem, so the failure may be duplicated and repaired

  • Failing to clear the ECM codes after the codes are fixed

  • Diagnosing code P2104 before diagnosing other throttle control system codes first

How serious is the P2104 code?

Code P2104 is an indication that the ECM is in failure management mode and has limited the RPM of the engine since the throttle control actuator system has a failure. The problem may be in another system as well causing a problem.

What repairs can fix the P2104 code?

  • Diagnosing and repairing other codes received for the TAC first before addressing code P2104

  • Removing an obstruction that is holding the accelerator open, like a carpet or floor mat

Additional comments for consideration regarding the P2104 code

Code P2104 is an informational code most of the time to alert you to another failure that caused the failure mode to be engaged and caused the engine to only idle. The most common cause of the code is starting the vehicle with the throttle held open during starting the engine.

Need help with a P2104 code?

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The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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