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DTC codes / P21xx · Fuel and air metering / P2104

P2104Throttle Actuator Control System - Forced Idle

P2104 means the engine computer has commanded the throttle actuator control system into a forced idle mode, where the throttle blade is held at a default idle position and driver pedal input is ignored. The computer detected a fault in the throttle actuator control circuit or its related sensors that prevents safe normal throttle operation, so it defaults to a high-idle or fixed-idle strategy to protect the engine and vehicle.

SystemPowertrain
Code typeGeneric (all makes)
SeverityHigh
Fix difficultyProfessional
AreaFuel and air metering

Symptoms you may notice

  • The engine idles at a fixed, often elevated speed and does not respond to the accelerator pedal
  • The accelerator pedal feels dead or unresponsive when pressed
  • The electronic throttle control warning light or reduced power message appears on the dash
  • The vehicle may enter limp mode and be limited to low speed
  • The engine may stall or hesitate when coming to a stop
  • Often no symptoms besides the warning light if the fault is intermittent

Common causes, most likely first

  1. Faulty throttle body assembly with a sticking or failed actuator motor
  2. Damaged or corroded wiring or connector at the throttle body or accelerator pedal sensor
  3. Failed accelerator pedal position sensor or its circuit
  4. Throttle position sensor signal out of range or intermittent
  5. Engine computer software or calibration issue requiring a reflash
  6. Poor ground connection for the throttle actuator control system
  7. Contamination or carbon buildup on the throttle plate causing binding

How to diagnose and fix it

  1. Scan all modules for stored and pending codes, and record freeze-frame data to understand when the fault occurred
  2. Inspect the throttle body, connector, and wiring for corrosion, chafing, or loose pins
  3. Check the accelerator pedal position sensor readings on a scan tool while slowly pressing and releasing the pedal
  4. Command the throttle actuator with a bidirectional scan tool and observe whether the throttle plate moves smoothly through its range
  5. Clean the throttle body and perform a throttle relearn or idle relearn procedure if contamination is found
  6. Check powers and grounds at the throttle body and engine computer, and repair any high resistance
  7. If the actuator or sensor is proven faulty, replace the throttle body assembly and perform the required calibration

Forced idle is not always a bad throttle body

  • A weak battery or poor ground can cause the throttle actuator control system to set P2104 because the actuator motor needs stable voltage to move the blade.
  • Many technicians replace the throttle body only to find a corroded connector pin or a chafed wire in the harness that was the real cause of the forced idle command.
  • The accelerator pedal sensor and the throttle body are a matched pair on many systems, so a fault in either one can trigger P2104 even though the throttle body itself is fine.
  • After any repair involving the throttle body or pedal sensor, a relearn or calibration procedure is required, or the code may return immediately.
  • P2104 can be set by a momentary voltage drop during cranking, so check for a stored history code before condemning parts.

Can I keep driving with P2104?

Do not drive the vehicle with P2104 active because the throttle may be stuck at idle or a fixed speed, making acceleration unpredictable and unsafe in traffic. Have the vehicle towed or driven only a very short distance to a safe repair location at low speed.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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