Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Low or High Power Supply Voltage (C1241)

Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual / Drivetrain / Mf1a (transfer / 4wd / Awd) / Dynamic Torque Control Awd System / Low or High Power Supply Voltage (C1241)

DESCRIPTION

If a malfunction in the power source circuit occurs, or a communication malfunction with the skid control ECU (brake actuator assembly) or speed sensor occurs, the 4WD ECU assembly prohibits operation.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

C1241

Low or High Power Supply Voltage
  • When the following continues for 10 seconds or more:
    • At a vehicle speed of 3 km/h (2 mph) or more, voltage of IG1 terminal is 9.5 V or less.
  • When either of the following is detected:
    • With the IG1 terminal voltage 9.5 V or less, communication with the skid control ECU (brake actuator assembly) is not possible.
    • Vehicle speed sensor voltage is abnormally low for 60 seconds or more.
  • When the following continues for 3 seconds or more:
    • With the IG1 terminal voltage 17 V or more, communication with the skid control ECU (brake actuator assembly) is not possible.
  • Battery
  • Charging system
  • Wire harness and connector (IG1 circuit, GND circuit)
  • Vehicle stability control system
  • CAN communication system
  • 4WD ECU assembly

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • Inspect the fuses for circuits related to this system before performing the following inspection procedure.
  • When the 4WD ECU assembly is replaced with a known good one from another vehicle, it is necessary to perform calibration.

    Click here

HINT:

Check the condition of each related circuit connector before troubleshooting.

Click here

PROCEDURE

1.

CHECK FOR DTC (CAN COMMUNICATION SYSTEM AND VEHICLE STABILITY CONTROL SYSTEM)

(a) Check if CAN communication DTCs are output.

Click here

(b) Start the engine.

(c) Drive the vehicle, accelerate to a speed of 3 km/h (2 mph) or more for 60 seconds or more, and check if any DTCs related to a speed sensor are output.

Chassis > Brake/EPB > Trouble Codes

Result

Proceed to

CAN communication system DTCs and vehicle stability control system DTCs are not output

A

CAN communication DTCs are output

B

Vehicle stability control system DTCs are output

C

HINT:

If CAN communication DTCs are output, perform troubleshooting for the CAN communication system first.

B

GO TO CAN COMMUNICATION SYSTEM (HOW TO PROCEED WITH TROUBLESHOOTING)

C

REPAIR CIRCUIT INDICATED BY OUTPUT CODE (VEHICLE STABILITY CONTROL SYSTEM)

A

2.

INSPECT BATTERY

(a) Check the battery voltage.

Standard Voltage:

11 to 14 V

NG

CHECK CHARGING SYSTEM

OK

3.

CHECK HARNESS AND CONNECTOR (IG1 TERMINAL)

(a) Disconnect the R10 4WD ECU assembly connector.

(b) Turn the engine switch on (IG).

(c) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

R10-3 (IG1) - Body ground

Engine switch on (IG)

11 to 14 V
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

4.

CHECK HARNESS AND CONNECTOR (GND TERMINAL)

(a) Turn the engine switch off.

(b) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

R10-4 (GND) - Body ground

Always

Below 1 Ω
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

5.

RECONFIRM DTC

(a) Connect the R10 4WD ECU assembly connector.

(b) Clear the DTCs.

Click here

Chassis > Four Wheel Drive > Clear DTCs

(c) Start the engine.

(d) Drive the vehicle, accelerate to a speed of 3 km/h (2 mph) or more for 60 seconds or more, and check if the same DTC is output.

Click here

Chassis > Four Wheel Drive > Trouble Codes

Result

Proceed to

DTCs are output

A

DTCs are not output

B
A

REPLACE 4WD ECU ASSEMBLY

B

CHECK FOR INTERMITTENT PROBLEMS

    Linear Solenoid Power Supply System Malfunction (C120C)
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    Engine Circuit Malfunction (C1280)
    DESCRIPTION If a malfunction in the ECM circuit is detected, the 4WD ECU assembly stores this DTC. DTC No. Detection Item DTC Detection Condition Trouble Area C1280 Engine Circuit Malfu ...

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    Lexus RX (RX 350L, RX450h) 2016-{YEAR} Owners Manual

    Lexus RX (RX 350L, RX450h) 2016-{YEAR} Repair Manual

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