P2104

Symptoms

• Engine held at idle with little or no throttle response
• decreased engine performance / limp mode with limited engine speed
• idle that may drop below normal range with rough running that can progress to stalling just after start
• shifting problems
• illuminated Check Engine Light
• illuminated ABS light on some vehicles.

Probable causes

• 1) Faulty electronic throttle body (including a throttle motor overheating or sticking from carbon buildup around the butterfly plate). 2) Accelerator pedal position (APP) sensor assembly failure
• including disagreement between the two pedal sensor signals. 3) Throttle position sensor failure. 4) Damaged wires or poor electrical connections in the ETC circuits. 5) ECM/PCM communication faults or PCM software requiring an update.

Diagnostic steps

1. Scan for all stored codes - P2104 is a fail-safe response, so diagnose any accompanying throttle actuator / APP / TPS codes first, with freeze frame data.
2. Visually inspect the ETC wiring and connectors (throttle body and accelerator pedal) for damage, corrosion, and loose pins.
3. Inspect the throttle body for carbon buildup around the throttle plate and for a sticking or binding plate; clean if the manufacturer permits.
4. Test the APP sensor signals for correlation - disagreement between pedal sensors forces idle.
5. Test the throttle position sensor outputs against specification.
6. Verify PCM communication and check for manufacturer software updates.
7. Clear codes, road test, and confirm the forced-idle condition does not return. Diagnosis and repair steps vary by vehicle - consult the model-specific repair manual.