P1125

Code

LEXUS P — Powertrain

Throttle Control Motor Circuit Malfunction

Brand: LEXUS

Type: P — Powertrain

Views: UK: 20 EN: 70 RU: 37

AI status

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Page language: EN

Causes

Blown fuse or fusible link for throttle actuator circuit
Low battery or poor battery connections/charging system
Corroded, loose, damaged or disconnected wiring/connectors to the throttle actuator motor
Open or shorted motor windings in the throttle control motor
Poor or missing ground at the throttle body or ECM
Faulty throttle body assembly (actuator motor) or ECM/software fault

Symptoms

Check Engine Light (MIL) illuminated
Engine may go into limp mode or have reduced throttle response
Delayed or unresponsive accelerator/pedal input
Erratic idle or stalling possible
Stored throttle-related fault codes and limited performance

What to check

Read and record all stored DTCs and freeze frame data with a scan tool
Verify battery voltage and charging system health (battery >= 12.4 V at rest)
Inspect fuses and relays related to throttle/ECM power
Visually inspect throttle body connector and wiring for damage, corrosion, or loose pins
Backprobe connector to monitor motor supply, ground, and control signals while observing vehicle behavior
Check for related codes (pedal position sensors, ECM communication) that may affect diagnosis

Signal parameters

Key On Engine Off (KOEO): throttle actuator supply should have battery voltage at the power feed (approx. 12 V)
Motor control lines: PWM/duty or driven outputs from ECM—variable duty cycle when commanded, often 0–100% range
Motor winding resistance: low ohms expected (motor should not be open circuit); exact value is model-specific—look for open/short
Current draw: actuator may draw up to a few amps under movement; excessive or no current indicates problem
Connector pin voltages should be stable; intermittent or noisy signals suggest poor connection or harness damage

Diagnostic algorithm

Retrieve all codes and freeze frame data; clear codes and attempt to reproduce to confirm persistence.
Verify battery voltage and charging; charge or replace battery if low and retest.
Inspect fuses/relays related to throttle actuator and replace if blown.
Visually inspect throttle body harness and connector for corrosion, bent pins, or damage; repair as needed.
With connector connected, backprobe power and ground circuits at the throttle body. Confirm KOEO battery voltage on power feed and good ground.
Using a scan tool, command the throttle actuator while monitoring actuator control signal, motor response, and current draw. Observe for proper movement and signals.
If no movement or improper signals, isolate by disconnecting connector and measure motor winding resistance for open/short. If motor is open/shorted, replace throttle body.
Perform wiggle test on wiring harness while monitoring signals for intermittent faults. Repair broken wires or damaged pins.
If wiring and motor check good, check continuity between throttle connector and ECM pins. Repair any high resistance or opens.
If circuit and motor are good but fault persists, consider ECM output driver failure; consult manufacturer service information and consider ECM testing/replacement as last resort.
After repairs, clear codes and perform a functional relearn/idle/ETC learning procedure per manufacturer, then road test and recheck for codes.

Likely causes

Damaged or disconnected harness connector at the throttle body
Open or short in the actuator motor circuit (wiring or motor)
Blown fuse or poor battery/ground affecting actuator supply
Failed throttle control motor (mechanical/electrical)
Intermittent connection due to corrosion or pin damage

Fault status

⚠️ Status

Throttle Control Motor Circuit Malfunction — ECM detected abnormal electrical condition in the throttle actuator motor circuit (open, short, high resistance, or intermittent).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours

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P1125 — Throttle Control Motor Circuit Malfunction