P1127

Code

SCION P — Powertrain

ETCS actuator power source circuit

Brand: SCION

Type: P — Powertrain

Views: UK: 1 EN: 3 RU: 4

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Page language: EN

Causes

Blown fuse or faulty power relay for ETCS/throttle actuator
Open, shorted or corroded wiring in power or ground circuit to throttle actuator
Loose, corroded or damaged connector at the throttle body
Failed throttle actuator/motor inside the throttle body
Faulty engine control module (ECM) or driver transistor
Low battery voltage or poor battery/charging system condition

Symptoms

Check Engine MIL illuminated
Reduced engine power / limp mode
Poor or no throttle response; hesitation on acceleration
Rough idle or stalling in some cases
Stored DTCs related to throttle control (additional ETCS codes)
Possible failure to start if actuator not powered

What to check

Read and record all stored codes and freeze-frame data with a scan tool
Check battery voltage (engine off and cranking) and charging system health
Inspect ETCS/throttle body fuse(s) and relay(s); check continuity and operation
Visually inspect throttle body connector and wiring for damage, corrosion, pin push-out
Backprobe throttle actuator power and ground pins with ignition ON; measure voltage and continuity
Wiggle wiring harness while monitoring voltage and scan tool for code changes

Signal parameters

Ignition-switched supply voltage to actuator: typically ~10–14 V with ignition ON (engine may be off)
Ground: near 0 V (low resistance to chassis ground); check continuity to battery negative
Control signals from ECU may be PWM; amplitude can approach battery voltage — refer to manufacturer data
Actuator/motor coil resistance: typically low (approx. 0.5–5 Ω) — consult service manual for exact value
Open or short condition: supply absent (

Diagnostic algorithm

Connect an OBD-II scanner, record P1127 and any related ETCS/throttle codes and freeze-frame data.
Check battery state-of-charge and charging system; ensure battery >=12.4 V at rest and >=10 V while cranking.
Inspect and test ETCS/throttle fuse(s) and relay(s). Replace any blown fuse and retest.
Visually inspect the throttle body connector and wiring harness for damage, corrosion, chafing or water intrusion. Repair damaged wiring or connector pins.
Backprobe the throttle actuator power feed and ground with ignition ON (engine OFF). Verify supply voltage (~10–14 V) and good ground. If supply is missing, trace upstream to fuse/relay/ignition switch.
With the connector disconnected, check continuity between the power source fuse output and the throttle connector power pin; check continuity from throttle ground pin to chassis/battery negative.
If supply and ground are present, measure actuator motor coil resistance per service spec. A very high/OL or very low/near-zero reading indicates internal actuator fault.
If wiring and actuator check good, test for shorts to battery or ground using an ammeter in-line or insulation tester where appropriate.
If wiring and actuator appear good but intermittent behavior persists, wiggle test harness while monitoring live data; repair any intermittent wiring faults.
If all wiring and actuator tests pass and replacement parts are available, consider replacing the throttle body/actuator. Replace ECM only after confirming actuator and wiring are good and per manufacturer diagnostic flow.
After repairs, clear codes, perform throttle relearn/calibration if required, then verify repair with road/test drive and re-scan for codes.

Likely causes

Blown fuse or bad ETCS relay
Damaged power feed wire between battery/ignition-switched source and throttle body
High resistance ground or broken ground strap
Internal short or open in throttle actuator motor
Corroded/loose throttle body connector pins
Faulty ECM driver stage (less common)

Fault status

⚠️ Status

ETCS actuator power source circuit — the ECM detected abnormal or missing power/ground to the electronic throttle actuator (open/short/high resistance).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.5 hours

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P1127 — ETCS actuator power source circuit