Throttle Actuator Control Motor Circuit Low
Diagnostic trouble code P2102 indicates that the Powertrain Control Module (PCM) has detected a voltage signal from the Throttle Actuator Control (TAC) motor circuit that falls below the expected threshold. This low voltage condition typically points to an open circuit, a short to ground, or an internal failure within the electronic throttle body motor.
This code is highly urgent because a failure in the electronic throttle control system will typically force the vehicle into a reduced power 'limp mode'. Driving in this condition can be unsafe, and the vehicle may stall or fail to accelerate.
Common symptoms
- Illuminated Check Engine Light
- Vehicle enters reduced power or 'limp' mode
- Little to no response when pressing the accelerator pedal
- Rough or erratic engine idle
- Engine stalling or hesitation
Likely causes
- Faulty throttle actuator control motor (internal throttle body failure)
- Damaged, corroded, or loose electrical connector at the throttle body
- Wiring harness open circuit or short to ground in the TAC motor circuit
- Binding or carbon buildup preventing the throttle valve from moving
- Faulty Powertrain Control Module (PCM) (rare)
What to check before replacing parts
Visually inspect the throttle body electrical connector and wiring harness.
Look for: Look for pushed-out pins, severe corrosion, frayed wires, or signs of melting that could cause an open circuit or short to ground.
Use a scan tool to monitor commanded versus actual throttle position.
Look for: If the actual throttle position does not change when the accelerator is pressed or when commanded by the scanner, the motor or circuit is unresponsive.
Measure the internal resistance of the throttle actuator control motor using a multimeter.
Look for: Compare the resistance reading to the manufacturer's specifications; an infinite reading (OL) indicates an internal open circuit, while a near-zero reading indicates an internal short.
Check for proper voltage and ground signals at the TAC motor connector while the key is ON.
Look for: A lack of voltage or a missing ground indicates a wiring issue between the PCM and the throttle body, rather than a failed motor.
Inspect the throttle plate for physical binding or excessive carbon buildup.
Look for: With the engine off, gently push the throttle plate to ensure it moves freely and springs back; heavy resistance or sticking can overload the motor circuit.
This page explains the generic P2102 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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