OBD-II reference

All 9.533 generic OBD-II codes, explained in detail.

Causes, inspection steps and sources — a comprehensive DIY archive. Created and maintained with love for the detail. Good luck and have fun!

Powertrain generic / SAE

P2104

Throttle Actuator Control System — Forced Idle

The ECU has detected a fault severe enough that it forces the throttle actuator to the idle stop. The driver loses pedal authority — only idle is available until the underlying TAC fault clears.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number1 / 04

Possible causes

  • Severe upstream TAC fault high
  • Throttle position signal invalid medium

Symptoms

  • Check engine light on
  • Reduced throttle response, possible limp mode
  • Hesitation or surging
  • Idle too high or too low

Inspection / repair

  • Difficulty: hard
  • DIY: shop recommended
  • Estimated cost: 120–900 €
  • Estimated time: 1–4 h
  • Component: throttle actuator control
  • Component: ecm
  • MIL / check engine light
  • emissions-relevant
  • drive cycle required
  • limp mode possible

Sources

References

How to read OBD-II codes

The first letter names the vehicle system, the second digit distinguishes generic from manufacturer-specific, the remaining digits group fault area and number.

PPowertrain: engine, transmission, emissions
BBody: chassis trim, comfort, interior
CChassis: suspension, brakes, steering
UNetwork: CAN, control modules, communication