P2102 Code: Throttle Actuator Control Motor Circuit Low

What the P2102 code means

With an electronic throttle (drive by wire), there is no cable between the pedal and the throttle. The computer reads the pedal, works out how far the throttle should open and moves it with a small electric motor. Two position sensors on the throttle and two more on the pedal confirm that everything agrees. If it sees a mismatch, it goes into a limp mode that limits power to avoid unwanted acceleration.

The computer watches the control circuit from its own driver transistor. The P2102 code is stored when it sees low voltage in that circuit, which means a short to ground or a loss of power. Before you replace the part, check the fuse, relay, connector and wiring, because those are the most common causes.

The motor is run by a transistor bridge inside the computer, which can reverse polarity to open or close the throttle.

To confirm it, unplug the component with the key on and see what happens to the reading or the code. If the value jumps to the opposite extreme, the wiring is fine and the component is the one pulling the signal to ground. If nothing changes, look for the short in the wire, starting where the harness rubs against the engine, the chassis or the exhaust.

P2102 code symptoms

• Check engine light or another warning light on.
• Limp mode with limited power.
• High or unstable idle.

Likely causes of the P2102 code

1. Control wire shorted to ground. The component can end up stuck on, or the computer shuts off the command to protect itself.
2. Interrupted power supply. A blown fuse, a bad relay or a cut wire.
3. Shorted component. Its resistance is much lower than the specification.
4. Connector with moisture. It creates a path to ground.

How to diagnose the P2102 code step by step

1. Activate the component with the scan tool and check whether it responds.
2. Check the fuse and relay. Measure voltage on both sides of the fuse and swap the relay with an identical one.
3. Measure the supply at the connector. You should see battery voltage with the key on or when the component is activated.
4. Measure the component resistance and compare it with the manual. Also check its insulation to ground.
5. Check the control wire for continuity back to the computer and for any short circuit.

How to fix the P2102 code

• Repair the connector, the wiring or the power supply.
• Replace the electronic throttle motor if it does not respond when it gets correct power and a correct command.
• Clear the codes and verify the repair.

Technical reference data

• Throttle motor: typical resistance of 1 to 5 ohms, driven by PWM with reversible polarity.
• Position sensors: two signals, often one rising and one falling, that must add up to a constant value.
• After cleaning or replacing the throttle body, the idle position usually has to be relearned.
• These are general reference values, so check the manufacturer data for your vehicle.

Brand-specific notes

This system is everywhere. Chevrolet, Ford, Nissan, Toyota, Hyundai, Kia, Volkswagen and Renault use it on almost all of their current gasoline engines. Dirt in the throttle body is the most repeated cause on these vehicles.

If the throttle body looks dirty, clean it and run the relearn procedure, but do not skip the electrical tests, because a dirty throttle and a shorted circuit are different problems.

Frequently asked questions about P2102