Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Check Bus 5 Line for Short to GND

Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual / Power Source & Network / Networking / Can Communication System / Check Bus 5 Line for Short to GND

DESCRIPTION

There may be a short circuit between one of the CAN bus lines and GND when there is no resistance between terminal 15 (CA5H) of the network gateway ECU and terminal 4 (CG) of the DLC3, or terminal 16 (CA5L) of the network gateway ECU and terminal 4 (CG) of the DLC3.

Symptom

Trouble Area

No resistance exists between terminal 15 (CA5H) of the network gateway ECU and terminal 4 (CG) of the DLC3, or terminal 16 (CA5L) of the network gateway ECU and terminal 4 (CG) of the DLC3.
  • Short in CAN main bus line
  • Short in CAN branch line
  • Certification ECU (smart key ECU assembly)
  • Combination meter mirror ECU (headup display) (w/ Headup Display System)
  • Headlight ECU sub-assembly LH (w/ Automatic Headlight Beam Level Control System)
  • Combination meter assembly
  • Air conditioning amplifier assembly
  • Main body ECU (multiplex network body ECU)
  • Network gateway ECU
  • No. 5 CAN junction connector

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.

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  • 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 5 km/h (3 mph) or more for 52 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.

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  • Before replacing the certification ECU (smart key ECU assembly), refer to the smart access system with push-button start (for Start Function) Precaution.

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  • If the main body ECU (multiplex network body ECU) is replaced, refer to Registration.

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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 SHORT TO GND IN CAN BUS LINE (NETWORK GATEWAY ECU)

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

(b) Disconnect the J75 network gateway ECU connector.

*A

for DLC3 Connector Type A

*B

for DLC3 Connector Type B

*1

DLC3

-

-

*a

Front view of wire harness connector

(to Network Gateway ECU)

-

-

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

Standard Resistance:

for DLC3 Connector Type A

Tester Connection

Condition

Specified Condition

J75-15 (CA5H) - J12-4 (CG)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

J75-16 (CA5L) - J12-4 (CG)
for DLC3 Connector Type B

Tester Connection

Condition

Specified Condition

J75-15 (CA5H) - J141-4 (CG)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

J75-16 (CA5L) - J141-4 (CG)
OK

REPLACE NETWORK GATEWAY ECU

NG

2.

CHECK FOR SHORT TO GND IN CAN BUS LINE (NO. 5 CAN JUNCTION CONNECTOR)

(a) Disconnect the J97 No. 5 CAN junction connector.

*A

for DLC3 Connector Type A

*B

for DLC3 Connector Type B

*1

DLC3

-

-

*a

Front view of wire harness connector

(to No. 5 CAN Junction Connector)

*b

to Network Gateway ECU

*c

to Combination Meter Mirror ECU (Headup Display)

(w/ Headup Display System)

*d

to Headlight ECU Sub-assembly LH

(w/ Automatic Headlight Beam Level Control System)

*e

to Main Body ECU (Multiplex Network Body ECU)

*f

to Air Conditioning Amplifier Assembly

*g

to Combination Meter Assembly

*h

to Certification ECU (Smart Key ECU Assembly)

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

Standard Resistance:

for DLC3 Connector Type A

Tester Connection

Condition

Specified Condition

Connected to
*1: w/ Headup Display System

*2: w/ Automatic Headlight Beam Level Control System

J97-1 (CANH) - J12-4 (CG)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Network gateway ECU

J97-12 (CANL) - J12-4 (CG)

J97-2 (CANH) - J12-4 (CG)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Combination meter mirror ECU (headup display)*1

J97-13 (CANL) - J12-4 (CG)

J97-3 (CANH) - J12-4 (CG)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Headlight ECU sub-assembly LH*2

J97-14 (CANL) - J12-4 (CG)

J97-4 (CANH) - J12-4 (CG)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Main body ECU (multiplex network body ECU)

J97-15 (CANL) - J12-4 (CG)

J97-5 (CANH) - J12-4 (CG)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Air conditioning amplifier assembly

J97-16 (CANL) - J12-4 (CG)

J97-6 (CANH) - J12-4 (CG)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Combination meter assembly

J97-17 (CANL) - J12-4 (CG)

J97-7 (CANH) - J12-4 (CG)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Certification ECU (smart key ECU assembly)

J97-18 (CANL) - J12-4 (CG)
for DLC3 Connector Type B

Tester Connection

Condition

Specified Condition

Connected to
*1: w/ Headup Display System

*2: w/ Automatic Headlight Beam Level Control System

J97-1 (CANH) - J141-4 (CG)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Network gateway ECU

J97-12 (CANL) - J141-4 (CG)

J97-2 (CANH) - J141-4 (CG)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Combination meter mirror ECU (headup display)*1

J97-13 (CANL) - J141-4 (CG)

J97-3 (CANH) - J141-4 (CG)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Headlight ECU sub-assembly LH*2

J97-14 (CANL) - J141-4 (CG)

J97-4 (CANH) - J141-4 (CG)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Main body ECU (multiplex network body ECU)

J97-15 (CANL) - J141-4 (CG)

J97-5 (CANH) - J141-4 (CG)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Air conditioning amplifier assembly

J97-16 (CANL) - J141-4 (CG)

J97-6 (CANH) - J141-4 (CG)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Combination meter assembly

J97-17 (CANL) - J141-4 (CG)

J97-7 (CANH) - J141-4 (CG)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Certification ECU (smart key ECU assembly)

J97-18 (CANL) - J141-4 (CG)

Result

Proceed to

OK

A

NG (Network gateway ECU bus line)

B

NG (ECU or sensor bus line)

C
A

REPLACE NO. 5 CAN JUNCTION CONNECTOR
B

REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (NETWORK GATEWAY ECU - NO. 5 CAN JUNCTION CONNECTOR)
C

3.

CHECK FOR SHORT TO GND IN CAN BUS LINE (ECU, SENSOR)

(a) Reconnect all wire harness connectors.

(b) Disconnect the connector that includes terminals CANH and CANL from the ECU or sensor to which the bus line shorted to GND is connected.

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

*A

for DLC3 Connector Type A

*B

for DLC3 Connector Type B

*1

DLC3

-

-

*a

Component with harness connected

(Network Gateway ECU)

-

-

Standard Resistance:

for DLC3 Connector Type A

Tester Connection

Condition

Specified Condition

J75-15 (CA5H) - J12-4 (CG)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

J75-16 (CA5L) - J12-4 (CG)
for DLC3 Connector Type B

Tester Connection

Condition

Specified Condition

J75-15 (CA5H) - J141-4 (CG)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

J75-16 (CA5L) - J141-4 (CG)

HINT:

If the resistance changes to 200 Ω or higher when the connector is disconnected from the ECU or sensor, there may be a short in the ECU or sensor.

OK

REPLACE CORRESPONDING ECU OR SENSOR
NG

REPAIR OR REPLACE CORRESPONDING ECU OR SENSOR CAN BUS LINE OR CONNECTOR
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