Possible Causes

WARNING: This page is about a different car, the 2003 Infiniti G35. However, it is still accessible from the selected car via links, so may be relevant.

Malfunction is detected when:

Electric throttle control actuator does not function properly due to return spring malfunction.
Throttle valve opening angle in fail-safe mode is not in specified range.
ECM detect the throttle valve is stuck open. This self-diagnosis has the one trip detection logic.

ECM enters fail-safe mode when malfunction is detected. When malfunction "A" is detected, ECM controls electric throttle actuator by regulating throttle opening around idle position. The engine speed will not rise more than 2000 RPM.

When malfunction "B" is detected, ECM controls electric throttle control actuator by regulating throttle opening to 20 degrees or less.

When malfunction "C" is detected, the following occurs:

While vehicle is driving, it slows down gradually by fuel cut.
After vehicle stops, engine stalls.
The engine can restart in Park or Neutral, and engine speed will not exceed 1000 RPM.

NOTE: Perform following DTC confirmation tests in order.