What it means
Drive voltage to the throttle motor is below the lower limit. Typically a short to ground or a failed driver stage in the ECU.
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 motor is driven by a controlled electrical circuit that moves the throttle plate. P2102 sets when the control module detects the motor-drive circuit voltage below its expected lower limit, which can result from a short to ground, a motor fault, or poor connections.
Common causes
Most likely first.
- Drive line shorted to ground
- Throttle motor internal short
- Connector pins corroded - high contact resistance
Symptoms
- Check engine light on
- Reduced throttle response, possible limp mode
- Hesitation or surging
- Idle too high or too low
How to diagnose it
- Capture freeze-frame data and check for companion throttle codes before clearing anything, since they may help identify a shared power or wiring problem.
- Inspect the throttle-motor connector and harness for corrosion, pin damage, chafing, or wiring contacting ground.
- Check connector pin fit and terminal condition; corrosion or weak contact can create enough resistance to pull the drive circuit low.
- Following the wiring diagram and manufacturer's procedure, test the motor-drive circuit for a short to ground and verify its connections.
- If the harness checks out, test the throttle motor and control-module driver circuit against the manufacturer's specification.
Common fixes
- Clean and secure corroded or poorly seated throttle-motor connector terminals.
- Repair wiring shorted to ground or damaged insulation in the motor-drive circuit.
- Replace a throttle actuator motor that fails the specified test.
- Repair or replace a control module only if its driver is confirmed faulty after circuit checks.
Can I keep driving?
The vehicle may enter reduced-power mode, so avoid traffic situations that require quick acceleration. If the engine idles unpredictably or throttle control is unreliable, stop driving and arrange assistance.
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.