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DTC P1127: ELECTRONIC THROTTLE CONTROL SYSTEM (ETCS) ACTUATOR POWER SOURCE CIRCUIT MALFUNCTION Lexus LS III

CAUTIONIf ECM replacement is instructed in following testing, always ensure ECM harness connector and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction. If ECM is replaced, ECM must be programmed with proper ignition key code for engine immobilizer system. For programming procedures, see COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION.

Circuit Description

After ignition is turned off, battery voltage is still supplied to ECM for electronic throttle control system. If DTC P1127 is set, ECM shuts down power to throttle control motor and electromagnetic clutch. DTC P1127 is set when open in ETCS actuator power source circuit is detected. Possible causes are

  1. Open in ETCS actuator power source circuit.
  2. Faulty ECM.

Diagnostic Aids

Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.