Code
P2100
MERCEDES-BENZ
P — Powertrain
Throttle Actuator Control Motor Circuit/Open
Views:
UK: 16
EN: 27
RU: 41
AI status
Completed
Completed
100%
Causes
- Broken or disconnected wiring in throttle actuator motor circuit
- Corroded/loose connector at throttle actuator
- Failed throttle actuator (motor) or internal open winding
- Blown fuse or fusible link supplying throttle actuator circuit
- Poor ground or power supply to throttle actuator/ECM
- Faulty engine control module (less common)
Symptoms
- Check Engine Light / MIL illuminated
- Reduced engine power or limp-home mode
- Poor throttle response or no throttle control input
- Engine may idle poorly or not respond to accelerator
- Stored/active throttle-related DTCs (P21xx / P21xx series)
What to check
- Read freeze frame data and all stored/related DTCs with a scan tool
- Visually inspect throttle body connector, wiring harness and routing for damage, corrosion or pinch points
- Verify battery voltage is within normal range and battery is secure
- Check fuses and fusible links related to throttle/ECM power
- Back-probe throttle actuator connector pins and measure supply and ground with ignition ON and engine OFF
- Measure continuity and resistance of motor windings and wiring to ECM with connectors disconnected
Signal parameters
- Power supply: battery voltage present at throttle actuator power feed with ignition ON (approx. 11–14 V)
- Ground: solid reference/ground continuity to chassis/ECM ground
- Motor winding resistance: typically low ohms; expected non-infinite resistance (often in the 1–20 Ω range depending on design) — open/infinite indicates winding open
- ECM drive: PWM/H-bridge output — back-probed drive may show switching; voltage should change when actuator is commanded
- No high resistance: voltage drop between supply and actuator ground should be minimal under static load
Diagnostic algorithm
- Connect a scan tool, record freeze frame and note related codes. Clear codes and attempt to reproduce to confirm persistence.
- Visually inspect throttle body, connector, and wiring harness for damage, corrosion, loose pins, or signs of overheating or water entry.
- Check related fuses and relays; replace if blown and retest. Verify battery voltage is good.
- With ignition ON (engine OFF), back-probe the throttle actuator connector: check battery feed pin for ~12 V and ground/reference pin for continuity to chassis ground/ECM.
- Measure motor winding resistance at the throttle body connector with connector disconnected. Infinite or very high resistance indicates open winding — replace throttle actuator.
- Perform continuity/insulation checks on wiring between throttle actuator connector and ECM connector. Repair any open circuits or high-resistance sections.
- Command the throttle actuator using a scan tool (actuator calibration/drive test) while monitoring voltages and current if supported. Observe for correct movement and driver outputs from ECM.
- If wiring and actuator check OK, inspect ECM drive outputs at the ECU harness. If outputs are absent or shorted, consider ECM fault — consult manufacturer procedures before replacement.
- After repair, clear codes, perform throttle relearn/calibration as required by manufacturer, and perform road test to confirm fault is resolved.
Likely causes
- Open or high-resistance motor windings in the throttle actuator
- Damaged connector pins or corrosion at throttle body plug
- Broken wire or chafed harness between ECM and throttle body
- Blown fuse or interrupted power/ground feed to the actuator
- Water ingress or contamination at connector causing open circuit
Fault status
Status
Throttle actuator control motor circuit/open — open circuit in throttle motor drive; check wiring, connector and actuator motor.
Repair difficulty: Medium
Diagnostic time: 0.5-3.0 hours
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