Code
P1125
SCION
P — Powertrain
Throttle control motor circuit malfunction
Views:
UK: 2
EN: 6
RU: 3
AI status
Completed
Completed
100%
Causes
- Open or shorted wiring/harness to throttle control motor
- Poor or corroded connector or pin(s) at the throttle body
- Blown fuse or faulty relay for throttle motor power supply
- Faulty throttle body actuator (motor)
- Faulty Engine Control Module (ECM) or internal driver circuitry
- Intermittent connection due to vibration or damaged insulation
Symptoms
- Check Engine light (MIL) illuminated
- Reduced engine power / limp-home mode
- Throttle unresponsive to accelerator input or delayed response
- Erratic idle or stalling
- Possible stored multiple throttle-related DTCs
What to check
- Read and record all stored DTCs and freeze frame data with a scan tool
- Verify battery voltage is stable (12.4–14.5 V) with ignition on and engine running
- Visually inspect throttle body connector, wiring harness, and ground points for damage, corrosion or looseness
- Check for blown fuses/relays related to throttle control circuit
- Attempt an ECU-controlled throttle actuator test using a manufacturer scan tool (observe response)
- Check for other related codes (pedal position sensors, throttle position sensors)
Signal parameters
- Supply voltage to throttle motor: ~12 V (key ON); should be present and stable
- Ground continuity: near 0 ohms to chassis ground from motor ground circuit
- Actuator command: PWM duty or variable voltage from ECM (0–100% duty range depending on command)
- Throttle position feedback (TPS) sensor voltage: typically 0.5–4.5 V range across travel — should change smoothly with throttle movement
- Motor current draw: should be within expected range (typically low amps; high current suggests mechanical binding or short)
- Connector pin continuity: near 0 ohms for power/ground, open/very high resistance indicates break
Diagnostic algorithm
- Connect a professional scan tool, capture and record P1125 and any additional DTCs and freeze frame data. Attempt to replicate while monitoring live data (throttle command vs. throttle position).
- Verify battery/charging system: measure voltage at battery and at ECM/throttle connector with engine off and key on. Repair low voltage issues first.
- Visually inspect wiring and connector at the throttle body for damage, bent pins, corrosion, water intrusion or loose terminals. Repair or replace as needed.
- Check relevant fuses and relays for the throttle motor power circuit. Replace any blown fuses and re-test.
- With ignition ON (engine off), measure voltage at the throttle motor power terminal and check continuity to battery positive; measure continuity from motor ground terminal to chassis ground. Repair wiring faults.
- Backprobing: with scan tool commanding actuator (if supported), observe command signal and motor/feedback response. If command present but motor does not move, suspect motor or mechanical binding.
- Measure throttle motor resistance and compare to manufacturer specification; a shorted/open winding indicates motor failure. Also check for abnormal current draw when actuated.
- Clean throttle body if binding or contamination is present (follow manufacturer procedure).
- If wiring, fuses and motor check good but fault persists, consider replacement of throttle body assembly. After repair, clear codes and perform relearn/idle/ETC adaptations per manufacturer procedure and road test to confirm.
- If fault remains after replacing throttle body, test/replace ECM only after exhaustive verification of wiring and components.
Likely causes
- Damaged/corroded connector pins at throttle body
- Broken/disconnected power or ground wire to throttle motor
- Failed throttle actuator motor (no/erratic movement)
- Blown fuse supplying throttle motor
- Contamination or carbon buildup causing throttle sticking
Fault status
Status
ECM detected malfunction in the throttle control motor circuit (P1125). The condition may trigger reduced power mode and requires inspection of power/ground/command wiring, connectors, throttle actuator, and related fuses or ECM outputs.
Repair difficulty: Medium
Diagnostic time: 1.0-3.0 hours
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