What it means
Throttle/fuel inhibit A reads stuck high — short to battery voltage. ECM cannot read the inhibit state and falls back to the safe default.
At a glance
- Usually lights the check-engine light
How it works
The throttle/fuel inhibit circuit A carries a safety request that can restrict throttle or fuel delivery. The ECM sets P2555 when the input is above its expected range, often because the signal is shorted to battery voltage, leaving the inhibit state unreadable.
Common causes
Most likely first.
- Inhibit wire shorted to battery voltage
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Check-engine light
- Engine may not start or may stall
- Reduced or inconsistent throttle response
How to diagnose it
- Save freeze-frame data and check live data for inhibit A to confirm that the input remains high when no inhibit should be active.
- Inspect the inhibit A wire for contact with a battery-positive supply, pinching, damaged insulation, or a poor connector connection.
- Check the connector for corrosion, loose terminals, and pins pushed back into the housing.
- With the wiring diagram, test the signal for a short to battery voltage and check circuit continuity according to the manufacturer's specification.
- If the harness tests correctly, check the inhibit input device and the connected module's output for an unintended high signal.
Common fixes
- Repair a pinched or chafed inhibit A wire contacting a voltage source.
- Clean and secure the inhibit A connector or replace damaged terminals.
- Repair a short to battery voltage in the signal circuit.
- Replace a faulty inhibit input device if it continues to produce a high reading with sound wiring.
- Repair the connected module if its output remains high when the inhibit request is inactive.
Can I keep driving?
If the engine stalls, will not start, or loses throttle response, do not drive it where a sudden loss of power could create danger. The ECM may be unable to determine whether the safety inhibit is active.
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.