Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: ECM Communication Stop Mode

Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual / Power Source & Network / Networking / Can Communication System / ECM Communication Stop Mode

DESCRIPTION

Detection Item

Symptom

Trouble Area

ECM Communication Stop Mode

Either condition is met:

  • "ECM (Engine)" is not displayed on the CAN Bus Check screen of the Techstream.

    Click here

  • Communication system DTCs (DTCs that start with U) that correspond to "ECM Communication Stop Mode" in "DTC Combination Table" are output.

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  • ECM main line or connector
  • Power source circuit of ECM
  • ECM ground circuit
  • ECM

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • Before measuring the resistance of the CAN bus, turn the engine switch off and leave the vehicle for 1 minute or more without operating the key or any switches, or opening or closing the doors. After that, disconnect the cable from the negative (-) battery terminal and leave the vehicle for 1 minute or more before measuring the resistance.
  • After turning the engine switch off, waiting time may be required before disconnecting the cable from the negative (-) battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) battery terminal notices before proceeding with work.

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  • Because the order of diagnosis is important to allow correct diagnosis, make sure to begin troubleshooting using How to Proceed with Troubleshooting when CAN communication system related DTCs are output.

    Click here

  • After performing repairs, perform the DTC check procedure and confirm that the DTCs are not output again.
  • DTC check procedure: Drive the vehicle at a speed of 60 km/h (37 mph) or more for 20 seconds or more. And drive the vehicle with the dynamic radar cruise control system operated for 4 seconds or more.
  • After the repair, perform the CAN bus check and check that all the ECUs and sensors connected to the CAN communication system are displayed.

    Click here

  • Inspect the fuses for circuits related to this system before performing the following procedure.

HINT:

  • Operating the engine switch, any other switches or a door triggers related ECU and sensor communication on the CAN. This communication will cause the resistance value to change.
  • Even after DTCs are cleared, if a DTC is stored again after driving the vehicle for a while, the malfunction may be occurring due to vibration of the vehicle. In such a case, wiggling the ECUs or wire harness while performing the inspection below may help determine the cause of the malfunction.

PROCEDURE

1.

CHECK FOR OPEN IN CAN BUS LINES (ECM MAIN LINE)

(a) Disconnect the cable from the negative (-) battery terminal.

(b) Disconnect the A37 ECM connector.

*a

Front view of wire harness connector

(to ECM)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A37-13 (CANH) - A37-26 (CANL)

Cable disconnected from negative (-) battery terminal

108 to 132 Ω
NG

REPAIR OR REPLACE CAN MAIN BUS LINES OR CONNECTOR (ECM)
OK

2.

CHECK ECM POWER SOURCE CIRCUIT

(a) Check the ECM power source circuit.

Click here

OK

REPLACE ECM

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)
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