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/ LEXUS Parking Assist-sensor System) Parking assist ECU (w/ Panoramic View Monitor System) Forward recognition camera (w/ Lexus Safety System +) Millimeter wave radar sensor assembly (w/ Lexus Safety System +) Front television camera assembly (w/ Panoramic View Monitor System) Driving support ECU assembly (w/ Lexus Safety System +) Side camera RH (outer rear view mirror assembly RH) (w/ Panoramic View Monitor System) Side camera LH (outer rear view mirror assembly LH) (w/ Panoramic View Monitor System) Rear television camera assembly (w/ Panoramic View Monitor System or Parking Assist Monitor System w/o Parallel Parking Assist Function) Blind spot monitor sensor LH (w/ Blind Spot Monitor System) Network gateway ECU No. 3 CAN junction connector No. 10 CAN junction connector

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/ LEXUS Parking Assist-sensor System)
Parking assist ECU (w/ Panoramic View Monitor System)
Forward recognition camera (w/ Lexus Safety System +)
Millimeter wave radar sensor assembly (w/ Lexus Safety System +)
Front television camera assembly (w/ Panoramic View Monitor System)
Driving support ECU assembly (w/ Lexus Safety System +)
Side camera RH (outer rear view mirror assembly RH) (w/ Panoramic View Monitor System)
Side camera LH (outer rear view mirror assembly LH) (w/ Panoramic View Monitor System)
Rear television camera assembly (w/ Panoramic View Monitor System or Parking Assist Monitor System w/o Parallel Parking Assist Function)
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

Note

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), wait for at least 20 seconds, and then drive the vehicle at a speed of 36 km/h (22 mph) or more for 32 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

Tech Tips

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

CHECK FOR SHORT IN CAN BUS LINES (NO. 3 CAN JUNCTION CONNECTOR)

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

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/ LEXUS Parking Assist-sensor System)
*e	to Millimeter Wave Radar Sensor Assembly (w/ Lexus Safety System +)	*f	to Front Television Camera Assembly (w/ Panoramic View Monitor System )
*g	to Driving Support ECU Assembly (w/ Lexus Safety System +)	*h	to Forward Recognition Camera (w/ Lexus Safety System +)
*i	to Side Camera RH (Outer Rear View Mirror Assembly RH) (w/ Panoramic View Monitor System)	*j	to No. 10 CAN Junction Connector

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*3
J95-5 (CANH) - J95-15 (CANL)	Cable disconnected from negative (-) battery terminal	200 Ω or higher	Millimeter wave radar sensor assembly*2
J95-6 (CANH) - J95-16 (CANL)	Cable disconnected from negative (-) battery terminal	200 Ω or higher	Front television camera assembly*1
J95-7 (CANH) - J95-17 (CANL)	Cable disconnected from negative (-) battery terminal	200 Ω or higher	Driving support ECU assembly*2
J95-8 (CANH) - J95-18 (CANL)	Cable disconnected from negative (-) battery terminal	200 Ω or higher	Forward recognition camera*2
J95-9 (CANH) - J95-19 (CANL)	Cable disconnected from negative (-) battery terminal	200 Ω or higher	Side camera RH (outer rear view mirror assembly RH)*1
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/ Lexus Safety System +
*3: w/ LEXUS Parking Assist-sensor System

Result

Result	Proceed to
OK	A
NG (Network gateway ECU main line)	B
NG (No. 10 CAN junction connector main line)	C
NG (ECU or sensor branch line)	D

REPLACE NO. 3 CAN JUNCTION CONNECTOR

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

GO TO STEP 4 Click here

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

*a
Front view of wire harness connector

(to Network Gateway ECU)

Disconnect the J75 network gateway ECU connector.

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

Result

Result
OK
NG

REPLACE NETWORK GATEWAY ECU Click here

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

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

Reconnect the J95 No. 3 CAN junction connector.

Disconnect the S56, S57, S58, S59 and S60 No. 10 CAN junction connectors.

Tech Tips

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.

Rear view of wire harness connector

(to No. 10 CAN Junction Connector)

to Network Gateway ECU

to No. 3 CAN Junction Connector

to Blind Spot Monitor Sensor LH

(w/ Blind Spot Monitor System)

to Rear Television Camera Assembly

(w/ Panoramic View Monitor System or Parking Assist Monitor System w/o Parallel Parking Assist Function)

to Side Camera LH (Outer Rear View Mirror Assembly LH)

(w/ Panoramic View Monitor System)

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
S60	B	W	Side camera LH (outer rear view mirror assembly LH)

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*1
S59-1 (CANH) - S59-2 (CANL)	Cable disconnected from negative (-) battery terminal	200 Ω or higher	Rear television camera assembly*2
S60-1 (CANH) - S60-2 (CANL)	Cable disconnected from negative (-) battery terminal	200 Ω or higher	Side camera LH (outer rear view mirror assembly LH)*3

*1: w/ Blind Spot Monitor System
*2: w/ Panoramic View Monitor System or Parking Assist Monitor System w/o Parallel Parking Assist Function
*3: w/ Panoramic View Monitor System

Result

Result	Proceed to
OK	A
NG (No. 3 CAN junction connector main line)	B
NG (ECU or sensor branch line)	C
NG (Network gateway ECU main line)	D

REPLACE NO. 10 CAN JUNCTION CONNECTOR

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

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

CHECK FOR SHORT IN CAN BUS LINES (ECU, SENSOR)

Reconnect all wire harness connectors.
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

*a	Component with harness connected (Network Gateway ECU)

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

Tech Tips

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.

Result

Result
OK
NG

REPLACE CORRESPONDING ECU OR SENSOR

REPAIR OR REPLACE CORRESPONDING ECU OR SENSOR BRANCH LINES OR CONNECTOR

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

*a
Front view of wire harness connector

(to Network Gateway ECU)

Disconnect the J75 network gateway ECU connector.

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

Result

Result
OK
NG

REPLACE NETWORK GATEWAY ECU Click here

REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (NETWORK GATEWAY ECU - NO. 10 CAN JUNCTION CONNECTOR)