What it means
The drive-by-wire throttle motor circuit is open — no current flow detected. The ECU loses authority over the throttle plate and forces a limp-home with reduced power.
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
The electronic throttle body uses an electric motor to move the throttle plate in response to accelerator and engine-control commands. The control module monitors the motor circuit for current flow; P2100 sets when it detects an open circuit and cannot drive the motor as expected.
Common causes
Most likely first.
- Throttle motor failed
- Connector loose or corroded
- Wiring break to throttle body
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 scan for related throttle and pedal codes to see what conditions accompanied the open-circuit fault.
- With the ignition off, inspect the throttle-body connector and motor wiring for a loose plug, corrosion, damaged insulation, or a broken conductor.
- Reconnect the plug securely and check whether the code returns after clearing it and running the engine under safe conditions.
- Use the wiring diagram to check continuity through the throttle-motor circuit and its connections, following the manufacturer's procedure.
- If the wiring and connections are intact, test the throttle actuator motor against the manufacturer's specification before considering a control-module fault.
Common fixes
- Reconnect or clean and secure a loose or corroded throttle-body connector.
- Repair a broken or damaged wire in the throttle-motor circuit.
- Replace a failed throttle actuator motor or throttle body, as applicable to the vehicle.
Can I keep driving?
Reduced power or limp mode can make merging and crossing traffic unsafe, so avoid high-speed or demanding driving. If throttle response is unreliable or the engine will not maintain a safe idle, stop somewhere safe and arrange recovery.
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.