OBD-II trouble code
P2102: Throttle Actuator 'A' Control Motor Circuit Low
Voltage on the electronic throttle motor's control circuit is being dragged low — most often a wire shorted to ground or a shorted motor winding. The ECM cuts throttle control and puts the vehicle into reduced power mode.
Quick facts
- System
- Powertrain
- Category
- Fuel & Air Metering
- Severity
- High severity
- Drivable
- No — stop driving until repaired
- Repair cost range
- $80 – $900
- DIY difficulty
- Intermediate DIY
What does P2102 mean?
The electronic throttle body contains a small DC motor that the engine control module (ECM) drives to open and close the throttle plate. The ECM doesn't just command that motor — it monitors the circuit while doing so, watching voltage and current to confirm the motor is responding the way it should. P2102 sets when the ECM sees voltage on the throttle actuator control circuit that is below the expected range.
A low reading on a driven circuit means something is pulling it toward ground. The classic cause is a chafed wire in the harness touching the engine block, a bracket, or the throttle body housing itself. The second most common cause is a shorted winding inside the throttle motor: as the insulation between windings breaks down, the motor draws far more current than it should and the driver circuit sags. Corroded connectors and water intrusion sit behind both of those as contributors, particularly on vehicles that have had a coolant leak or an engine bay wash.
There's a useful field test for separating harness faults from motor faults. Unplug the throttle body connector and clear the code, then key on. If the code changes to P2100 — an open circuit — the ECM is now seeing exactly what it should with nothing connected, which means the short was inside the throttle body. If P2102 persists with the throttle body disconnected, the throttle motor is out of the circuit and the short has to be in the harness between the ECM and the connector.
Because throttle authority is safety-relevant, the ECM's response is aggressive. It typically de-energizes the throttle motor entirely and lets the plate return to its spring-loaded default position, producing a hard reduced-power or limp mode with an accompanying warning light. The engine will idle and the vehicle will creep, but acceleration is essentially gone. That makes P2102 a stop-driving code in practice, even though nothing has mechanically failed in the engine. After any repair, perform the manufacturer's throttle relearn — skipping it leaves the ECM with stale closed-throttle values and often re-sets a code.
Common causes
- Chafed throttle motor wire shorted to ground against the block, a bracket, or the throttle body
- Shorted winding inside the electronic throttle body motor
- Water or coolant intrusion into the throttle body connector bridging pins to ground
- Corroded terminals creating an unintended ground path
- Damaged harness section from rodent chewing or a previous repair
- Aftermarket wiring, alarm, or remote start installation tapped into the wrong circuit
- Carbon-seized throttle plate forcing excessive motor current draw
- Failed ECM throttle driver (rare — confirm the harness and motor first)
Symptoms
- Check engine light with a throttle or reduced-power warning
- Severe power loss — the engine idles but will not accelerate normally
- Vehicle stuck in limp mode with limited RPM
- Rough, hunting, or unusually high idle at the throttle's default position
- Stalling, particularly on deceleration or at a stop
- Cruise control disabled
- Companion throttle codes such as P2100, P2101, or P2110 stored at the same time
Diagnostic steps
- 1.Record all codes and freeze frame data before clearing anything — note whether the fault appears at cold start or after warm-up.
- 2.Inspect the throttle body connector for coolant staining, water, corrosion, and burnt or backed-out terminals.
- 3.Unplug the throttle body, clear the code, and key on. A code that switches to P2100 points inside the throttle body; a P2102 that persists points at the harness.
- 4.With the connector unplugged and the key off, measure resistance from each motor circuit to a good chassis ground. A low reading confirms a short to ground.
- 5.Measure the motor's own resistance across its two pins and compare to specification. A reading well below spec indicates shorted windings.
- 6.Trace the harness from the ECM to the throttle body looking for chafe points, especially anywhere the loom crosses a metal edge or bracket.
- 7.Remove the throttle body and check that the plate moves freely by hand. A carbon-seized plate makes the motor draw excessive current.
- 8.After repair, perform the throttle relearn and verify in live data that commanded throttle position tracks actual position smoothly through the full range.
Repair cost
$80 – $900
A cleaning and relearn resolves the minority of cases where a seized plate was driving current draw, at $80-$200. Harness repair for a short to ground typically runs $150-$450 depending on how much loom has to be opened. Electronic throttle body replacement runs $300-$800 installed including the relearn, since the motor is integral to the assembly on nearly all vehicles.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with throttle body replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.