Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual: Check Bus 1 Lines for Short Circuit

Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual / Power Source & Network / Networking / Can Communication System / Check Bus 1 Lines for Short Circuit

DESCRIPTION

There may be a short circuit between the bus 1 main lines and/or bus 1 branch lines when the resistance between terminals 23 (CA1H) and 8 (CA1L) of the network gateway ECU is below 54 Ω.

Symptom

Trouble Area

Resistance between terminals 23 (CA1H) and 8 (CA1L) of network gateway ECU is below 54 Ω.
  • Short in CAN main bus line
  • Short in CAN branch line
  • Clearance warning ECU assembly (w/ Intuitive Parking Assist System)
  • Parking assist ECU (w/ Panoramic View Monitor System)
  • Forward recognition camera
  • Millimeter wave radar sensor assembly
  • Rear television camera assembly
  • Blind spot monitor sensor LH (w/ Blind Spot Monitor System)
  • Network gateway ECU
  • No. 3 CAN junction connector
  • No. 10 CAN junction connector

WIRING DIAGRAM

CAUTION / NOTICE / HINT

CAUTION:

When performing the confirmation driving pattern, obey all speed limits and traffic laws.

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.

    Click here

  • 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: Turn the engine switch on (IG) and wait for 1 minute or more. Then operate the suspected malfunctioning system and drive the vehicle at 60 km/h (37 mph) or more for 5 minutes 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

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 (NO. 3 CAN JUNCTION CONNECTOR)

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

(b) Disconnect the J95 No. 3 CAN junction connector.

*a

Front view of wire harness connector

(to No. 3 CAN Junction Connector)

*b

to Network Gateway ECU

*c

to Parking Assist ECU

(w/ Panoramic View Monitor System)

*d

to Clearance Warning ECU Assembly

(w/ Intuitive Parking Assist System)

*e

to Millimeter Wave Radar Sensor Assembly

*f

to Forward Recognition Camera

*g

to No. 10 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

J95-1 (CANH) - J95-11 (CANL)

Cable disconnected from negative (-) battery terminal

108 to 132 Ω

Network gateway ECU

J95-2 (CANH) - J95-12 (CANL)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Parking assist ECU*1

J95-3 (CANH) - J95-13 (CANL)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Clearance warning ECU assembly*2

J95-5 (CANH) - J95-15 (CANL)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Millimeter wave radar sensor assembly

J95-8 (CANH) - J95-18 (CANL)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Forward recognition camera

J95-10 (CANH) - J95-20 (CANL)

Cable disconnected from negative (-) battery terminal

108 to 132 Ω

No. 10 CAN junction connector
  • *1: w/ Panoramic View Monitor System
  • *2: w/ Intuitive Parking Assist System

Result

Proceed to

OK

A

NG (Network gateway ECU main lines)

B

NG (No. 10 CAN junction connector main lines)

C

NG (ECU or sensor branch lines)

D
A

REPLACE NO. 3 CAN JUNCTION CONNECTOR
C

GO TO STEP 3

D

GO TO STEP 4

B

2.

CHECK FOR SHORT IN CAN BUS LINES (NETWORK GATEWAY ECU - NO. 3 CAN JUNCTION CONNECTOR)

(a) Disconnect the J75 network gateway ECU connector.

*a

Front view of wire harness connector

(to Network Gateway ECU)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

J75-9 (CAXH) - J75-24 (CAXL)

Cable disconnected from negative (-) battery terminal

1 MΩ or higher
OK

REPLACE NETWORK GATEWAY ECU

NG

REPAIR OR REPLACE CAN MAIN BUS LINES OR CONNECTOR (NETWORK GATEWAY ECU - NO. 3 CAN JUNCTION CONNECTOR)

3.

CHECK FOR SHORT IN CAN BUS LINES (NO. 10 CAN JUNCTION CONNECTOR)

(a) Reconnect the J95 No. 3 CAN junction connector.

(b) Disconnect the S56, S57, S58 and S59 No. 10 CAN junction connectors.

HINT:

  • Connectors that connect to the CAN junction connector can be distinguished by the color of their CAN bus lines.
  • Before disconnecting the connectors, make a note of where they are connected.
  • Reconnecting the connectors to non-original positions on the CAN junction connector does not affect system performance. However, it is preferred to reconnect the connectors to their original positions to avoid negative effects on the wiring such as tension on the wiring harnesses, and to make future maintenance easier.

*a

Rear view of wire harness connector

(to No. 10 CAN Junction Connector)

*b

to Network Gateway ECU

*c

to No. 3 CAN Junction Connector

*d

to Blind Spot Monitor Sensor LH

(w/ Blind Spot Monitor System)

*e

to Rear Television Camera Assembly

-

-
Wiring Color:

Code

Color (CANH Side)

Color (CANL Side)

Connected to

S56

G

W

Network gateway ECU

S57

LG

W

No. 3 CAN junction connector

S58

V

W

Blind spot monitor sensor LH

S59

P

W

Rear television camera assembly

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

Connected to

S56-1 (CANH) - S56-2 (CANL)

Cable disconnected from negative (-) battery terminal

108 to 132 Ω

Network gateway ECU

S57-1 (CANH) - S57-2 (CANL)

Cable disconnected from negative (-) battery terminal

108 to 132 Ω

No. 3 CAN junction connector

S58-1 (CANH) - S58-2 (CANL)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Blind spot monitor sensor LH*

S59-1 (CANH) - S59-2 (CANL)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Rear television camera assembly
  • *: w/ Blind Spot Monitor System

Result

Proceed to

OK

A

NG (No. 3 CAN junction connector main lines)

B

NG (ECU or sensor branch lines)

C

NG (Network gateway ECU main lines)

D
A

REPLACE NO. 10 CAN JUNCTION CONNECTOR
B

REPAIR OR REPLACE CAN MAIN BUS LINES OR CONNECTOR (NO. 3 CAN JUNCTION CONNECTOR - NO. 10 CAN JUNCTION CONNECTOR)
D

GO TO STEP 5

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.

Click here

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

J75-23 (CA1H) - J75-8 (CA1L)

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

5.

CHECK FOR SHORT IN CAN BUS LINES (NETWORK GATEWAY ECU - NO. 10 CAN JUNCTION CONNECTOR)

(a) Disconnect the J75 network gateway ECU connector.

*a

Front view of wire harness connector

(to Network Gateway ECU)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

J75-23 (CA1H) - J75-8 (CA1L)

Cable disconnected from negative (-) battery terminal

1 MΩ or higher
OK

REPLACE NETWORK GATEWAY ECU

NG

REPAIR OR REPLACE CAN MAIN BUS LINES OR CONNECTOR (NETWORK GATEWAY ECU - NO. 10 CAN JUNCTION CONNECTOR)
    Open in Bus 1 Main Bus Line
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