What it means
The TPS signal voltage exceeds the upper acceptable threshold. As with P0122, limp-home mode is typical until the fault clears.
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
Throttle or pedal position sensor A sends a position signal to the module, which checks that signal against its expected operating range. P0123 sets when the A signal rises above the accepted upper limit, often because the signal is shorted to a supply or the sensor ground is open.
Common causes
Most likely first.
- Signal wire shorted to supply voltage
- Sensor ground broken
- TPS internally failed
Symptoms
- Check engine light on
- Reduced throttle response, possible limp mode
- Hesitation or surging
- Idle too high or too low
How to diagnose it
- Record freeze-frame data and check live sensor A input to confirm it is unusually high while the fault is present.
- Inspect the sensor A connector and wiring for a signal wire touching a supply, corrosion, broken insulation, or loose terminals.
- Check the sensor ground for an open or high-resistance connection using the manufacturer's wiring information.
- Test the signal circuit for a short to voltage and verify sensor ground and response against the manufacturer's specification.
- Compare other sensors on a shared reference circuit to determine whether the high reading is isolated to sensor A.
Common fixes
- Repair a signal wire shorted to supply voltage.
- Restore the sensor ground connection if it is broken or poor.
- Clean or repair a corroded or loose sensor connector.
- Replace throttle or pedal position sensor A if it fails testing.
Can I keep driving?
Throttle response may be restricted or unpredictable, and limp mode may activate. Avoid high-speed or heavy-traffic driving; stop if the vehicle no longer responds reliably to the pedal.
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.