What it means
The PCM detected a high input from the throttle/pedal position sensor or switch C circuit. This indicates a signal above the diagnostic threshold, but 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 is one of the throttle or accelerator-pedal position signals the PCM uses to judge driver demand and throttle position. The PCM compares this input with its expected range and with related position signals; P0228 sets when the C input rises above its calibrated high threshold.
Common causes
Most likely first.
- Signal wire open
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Check engine light on
- Reduced throttle response, possible limp mode
- Hesitation or surging
- Idle too high or too low
How to diagnose it
- Use a scan tool to record freeze-frame data and compare the C signal with the other throttle or pedal position readings to see when the high input occurred.
- With the ignition off, inspect the C sensor or switch connector for corrosion, pushed-back pins, and a poor fit.
- Trace the C signal wire and supply wiring for breaks, chafing, or contact with a battery-positive feed.
- With a scan tool, watch the C reading while slowly operating the pedal or throttle and gently moving the harness to look for a reading that stays high or changes unexpectedly.
- Test the C signal, reference supply, and ground against the vehicle wiring diagram and manufacturer's specification before replacing a sensor or PCM.
Common fixes
- Clean and secure corroded or loose C-circuit connector terminals.
- Repair an open or damaged C signal wire.
- Repair wiring pinched against a battery-positive source.
- Replace a confirmed faulty throttle or pedal position sensor assembly.
Can I keep driving?
Reduced or unpredictable throttle response can make merging and passing unsafe, so avoid high-speed driving and hard acceleration. If the engine surges, idles abnormally, or enters limp mode, stop somewhere safe and arrange repair.
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.