Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Check Bus 5 Lines for Short Circuit

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

DESCRIPTION

There may be a short circuit between the bus 5 main lines and/or bus 5 branch lines when the resistance between terminals 15 (CA5H) and 16 (CA5L) of the network gateway ECU is below 54 Ω.

Symptom

Trouble Area

Resistance between terminals 15 (CA5H) and 16 (CA5L) of network gateway ECU is below 54 Ω.
  • 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 IN CAN BUS LINES (NETWORK GATEWAY ECU)

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

(b) Disconnect the J75 network gateway ECU connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

J75-15 (CA5H) - J75-16 (CA5L)

Cable disconnected from negative (-) battery terminal

108 to 132 Ω

*a

Front view of wire harness connector

(to Network Gateway ECU)
OK

REPLACE NETWORK GATEWAY ECU

NG

2.

CHECK FOR SHORT IN CAN BUS LINES (COMBINATION METER ASSEMBLY)

(a) Reconnect the J75 network gateway ECU connector.

(b) Disconnect the J10 combination meter assembly connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

J10-29 (CANH) - J10-30 (CANL)

Cable disconnected from negative (-) battery terminal

108 to 132 Ω

*a

Front view of wire harness connector

(to Combination Meter Assembly)
OK

REPLACE COMBINATION METER ASSEMBLY

NG

3.

CHECK FOR SHORT IN CAN BUS LINES (NO. 5 CAN JUNCTION CONNECTOR)

(a) Reconnect the J10 combination meter assembly connector.

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

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

Connected to
*1: w/ Headup Display System

*2: w/ Automatic Headlight Beam Level Control System

J97-1 (CANH) - J97-12 (CANL)

Cable disconnected from negative (-) battery terminal

108 to 132 Ω

Network gateway ECU

J97-2 (CANH) - J97-13 (CANL)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Combination meter mirror ECU (headup display)*1

J97-3 (CANH) - J97-14 (CANL)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Headlight ECU sub-assembly LH*2

J97-4 (CANH) - J97-15 (CANL)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Main body ECU (multiplex network body ECU)

J97-5 (CANH) - J97-16 (CANL)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Air conditioning amplifier assembly

J97-6 (CANH) - J97-17 (CANL)

Cable disconnected from negative (-) battery terminal

108 to 132 Ω

Combination meter assembly

J97-7 (CANH) - J97-18 (CANL)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Certification ECU (smart key ECU assembly)

*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)

Result

Proceed to

OK

A

NG (Network gateway ECU main lines)

B

NG (ECU or sensor branch lines)

C

NG (Combination meter assembly main lines)

D
A

REPLACE NO. 5 CAN JUNCTION CONNECTOR
B

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

REPAIR OR REPLACE CAN MAIN BUS LINES OR CONNECTOR (COMBINATION METER ASSEMBLY - NO. 5 CAN JUNCTION CONNECTOR)
C

4.

CHECK FOR SHORT IN CAN BUS LINES (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 short circuited branch line is connected.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

J75-15 (CA5H) - J75-16 (CA5L)

Cable disconnected from negative (-) battery terminal

54 to 69 Ω

HINT:

If the resistance becomes normal (between 54 and 69 Ω) when the connector is disconnected from the ECU or sensor, there may be a short in the ECU or sensor.

*a

Component with harness connected

(Network Gateway ECU)
OK

REPLACE CORRESPONDING ECU OR SENSOR
NG

REPAIR OR REPLACE CORRESPONDING ECU OR SENSOR BRANCH LINES OR CONNECTOR
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