P2104 Code: Throttle Actuator Control System - Forced Idle
Note: We do not currently have verified model-specific diagnostic data for the Audi A4. The symptoms and fixes listed below are the standard generic OBD2 guidelines for the P2104 code. Always consult a factory service manual before replacing parts.
What does this mean?
Code P2104 relates to the electronic throttle actuator control (drive-by-wire) system. When this system fails, the vehicle typically enters reduced power or limp mode.
Diagnostic system: General powertrain circuit
On a Audi A4, the P2104 code should be diagnosed as part of the general powertrain circuit group. Related codes and live data from this same system can change the repair priority, so avoid replacing parts from the code name alone.
Most Common Causes for Audi A4
- Faulty electronic throttle actuator motor
- Dirty or faulty throttle body
- Faulty throttle position sensor (TPS)
- Damaged, chafed, or broken wiring harness
- Internal PCM/ECM failure
- PCM/ECM software needs update (TSB)
Symptoms to Watch For
- Check Engine Light is illuminated
- Vehicle enters reduced power / limp mode
- Poor acceleration or sluggish response
- Engine stalling or dying unexpectedly
- Erratic or fluctuating idle speed
- Abnormally high idle speed
Before replacing parts, check these first
- Record freeze-frame data and related codes before clearing the fault.
- Inspect wiring, connectors, vacuum lines, fluid leaks, and fuses tied to the named system.
- Use live data or a multimeter to confirm the failed circuit before replacing parts.
- Check for blown fuses, weak battery voltage, and damaged connectors before buying major parts.
How to Diagnose
Common Mistakes
Treating the code description as a parts list instead of verifying the circuit, operating conditions, and related codes. Always confirm the fault with freeze-frame data, live data, visual inspection, and circuit checks before spending money on parts.
Frequently Asked Questions
Can I drive with the P2104 code?
If the check engine light is solid, you can usually drive to a safe location or mechanic. If the light is flashing, pull over immediately to prevent catastrophic engine or catalytic converter damage.
Will the P2104 code clear itself?
Once the underlying problem is fixed, the engine computer will run its self-checks. If it passes over several drive cycles, the light will turn off automatically. You can also clear it immediately using an OBD2 scanner.
Will this code fail an emissions test?
Yes. If the Check Engine Light is on due to the P2104 code, your Audi will automatically fail an OBD2 plug-in emissions or smog test.
What should I check first for P2104?
Record freeze-frame data and related codes before clearing the fault. Inspect wiring, connectors, vacuum lines, fluid leaks, and fuses tied to the named system. Use live data or a multimeter to confirm the failed circuit before replacing parts.
Join the Discussion
Repair Estimate
Fuse, connector, wiring, cleaning, or basic inspection
Major component replacement after live data and circuit tests confirm failure
Includes parts and labor. May vary by location.
Costs vary widely; start with visual inspection and circuit confirmation to avoid unnecessary parts.
DIY Difficulty
Can usually be performed at home with basic hand tools.