What does it mean?
OBD II fault code is defined as “Throttle/Pedal Position Sensor/Switch C Circuit Intermittent”, and set when the PCM (Powertrain Control Module) detects a signal voltage from the TPS (Throttle Position Sensor) that does not correlate with the current engine speed. On most applications, a voltage or resistance deviation of more than 10% of the specified reference value will cause a code to be stored and the CHECK ENGINE light to be illuminated.
As a rule, the PCM will recognize a closed throttle as a zero, or close to a zero voltage/resistance value, but be sure to check the actual voltage/resistance for a closed throttle against values stated in the manual. Essentially, the TPS is a type of variable resistor that is attached to the throttle body, and it alters the throttle opening as the circuit resistance/voltage changes due to movements of the accelerator pedal.
The TPS relies on signals from the PCM (derived from the pedal) to actuate the throttle, on the one hand, while at the same time, supplying the PCM with precise information on how wide the throttle is open at any given time. To complete the circuit, there is another sensor attached to the accelerator. This is most commonly a Hall Effect sensor that generates a current when a moving part is moved through a magnetic field.
This signal is used by the PCM to actuate a mechanism (which can be a motor, solenoid, or other device) in the TPS to change the position of the throttle plate. Changes in the throttle opening serve to alert the PCM to make suitable adjustments to the ignition timing, VVT/VCS timing, and injector pulse width/duration to ensure peak engine performance under any given load.
NOTE: Code P0229 is only relevant to “drive-by-wire” systems in which there are no physical connections, such as throttle cables, between the accelerator pedal and the throttle plate/body. In some applications, there may be additional sensors and devices fitted to act as back-ups should a primary component or sensor fail. The image below shows a typical Throttle Position Sensor and its location.
Note: Regardless of the code and the system affected, the word “Intermittent” refers to the fact that there is a sporadic, unpredictable, or, well, intermittent fault in that system. The most likely causes of codes that relate to intermittent faults include poor connections in both live and ground circuits, as well defective switches, relays, and sensors.
Intermittent faults can be extremely difficult to trace and fix, since code readers generally do not specify in which part of the circuit the problem lays. For instance, the fault could be an intermittent interruption of the reference voltage (power supply), or, as often happens, the problem could be an intermittent break in the signal voltage to the PCM (Powertrain Control Module) due to a failing sensor, wiring issues, or defective electrical connector(s).
Note that the word “intermittent” often means different things to different applications; some systems will set a code the first time an intermittent fault occurs, while others will only do so after several failure cycles. In some cases, it may be necessary to allow the fault to worsen before an accurate and definitive repair can be made.