What it means
The PCM detected an intermittent signal from the throttle/pedal position sensor or switch C circuit. The code does not identify a specific wiring cause.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
- The engine or gearbox may go into limp mode
How it works
Sensor or switch C supplies one of the position signals the PCM uses to interpret throttle or accelerator-pedal movement. P0229 sets when the C-circuit signal drops in and out of its expected behavior rather than remaining consistently high or low; a loose connection or vibration-sensitive harness can cause this pattern.
Common causes
Most likely first.
- Connector loose or corroded
- Connector with intermittent contact under vibration
- Harness routed against vibrating component
Symptoms
- Check engine light on
- Reduced throttle response, possible limp mode
- Hesitation or surging
- Idle too high or too low
How to diagnose it
- Read freeze-frame data and check for related throttle or pedal codes to identify the conditions when the C signal became intermittent.
- Inspect the C connector for looseness, corrosion, damaged locks, or terminals that may lose contact when moved.
- Check the C-circuit harness where it passes near vibrating or moving parts for rubbing, tension, or a loose support.
- Graph the C position signal alongside the other position readings while operating the pedal and gently moving the connector and harness.
- If the dropout persists, test C-circuit continuity and connections using the wiring diagram and manufacturer's specification.
Common fixes
- Secure a loose C-circuit connector or harness support.
- Clean or replace corroded or damaged connector terminals.
- Repair chafed or broken wiring in the C circuit.
- Replace a position sensor assembly only if testing confirms an internal intermittent fault.
Can I keep driving?
Because the intermittent signal can suddenly reduce throttle response or trigger limp mode, avoid busy traffic, high speeds, and hard acceleration until the fault is repaired. Stop driving if throttle response becomes erratic or the engine surges.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.