CAN COMMUNICATION SYSTEM(w/ Central Gateway ECU) Check Bus 1 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 central gateway ECU and terminal 4 (CG) of the DLC3, or terminal 16 (CA5L) of the central gateway ECU and terminal 4 (CG) of the DLC3.

Symptom	Trouble Area
No resistance exists between terminal 15 (CA5H) of the central gateway ECU and terminal 4 (CG) of the DLC3, or terminal 16 (CA5L) of the central gateway ECU and terminal 4 (CG) of the DLC3.	Short to ground in bus 1 main lines Short to ground in bus 1 branch lines Central gateway ECU Forward recognition camera1 Driving support ECU assembly1 Millimeter wave radar sensor assembly1 Blind spot monitor sensor LH2 No. 4 CAN junction connector No. 5 CAN junction connector No. 2 CAN junction terminal

*1: w/ Lexus Safety System +
*2: w/ Blind Spot Monitor System

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: Drive the vehicle at a speed of 36 km/h (22 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 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.
Connectors that connect to the CAN junction connector can be distinguished by the color of their CAN bus lines. When the connectors have been disconnected from the CAN junction connector, 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.

PROCEDURE

CHECK FOR SHORT TO GND IN CAN BUS LINE (CENTRAL GATEWAY ECU)

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

Disconnect the H202 No. 4 CAN junction connector.

Tech Tips

Connectors that connect to the CAN junction connector can be distinguished by the color of their CAN bus lines.
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.

Text in Illustration
*a	Rear view of wire harness connector (to No. 4 CAN Junction Connector)	*b	to Central Gateway ECU

Text in Illustration
*a	Component with harness connected (Central Gateway ECU)

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

Standard Resistance

Tester Connection	Condition	Specified Condition
H193-15 (CA5H) - H193-10 (GND)	Cable disconnected from negative (-) battery terminal	200 Ω or higher
H193-16 (CA5L) - H193-10 (GND)	Cable disconnected from negative (-) battery terminal	200 Ω or higher

CHECK FOR SHORT TO GND IN CAN BUS LINE (CENTRAL GATEWAY ECU - NO. 4 CAN J/C) Click here

CHECK FOR SHORT TO GND IN CAN BUS LINE (BRANCH LINE)

Reconnect the H202 No. 4 CAN junction connector.
Text in Illustration

*a
Component with harness connected

(Central Gateway ECU)

Connect the probes of an electrical tester to terminals 15 (CA5H) and 10 (GND), or between terminals 16 (CA5L) and 10 (GND) of the H193 central gateway ECU connector.

While observing the resistance value shown on the tester, disconnect connectors (H204, H206, H205 and U26) from the No. 4 CAN junction connector or No. 5 CAN junction connector one by one until the resistance becomes normal (200 Ω or higher).

Tech Tips

Disconnect the branch line connectors other than CAN main bus line connector.
Connectors that connect to the CAN junction connector can be distinguished by the color of their CAN bus lines.
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.

Text in Illustration
*A	w/ Lexus Safety System +	*B	w/ Blind Spot Monitor System
*1	Forward Recognition Camera	*2	Driving Support ECU Assembly
*3	Millimeter Wave Radar Sensor Assembly	*4	Central Gateway ECU
*5	No. 4 CAN Junction Connector	*6	No. 2 CAN Junction Terminal
*7	Blind Spot Monitor Sensor LH	*8	No. 5 CAN Junction Connector

Text in Illustration
*a	Component without harness connected (No. 4 CAN Junction Connector)	-	-

Wiring Color
No. 4 CAN Junction Connector	Code	Color (CANH Side)	Color (CANL Side)
Millimeter wave radar sensor assembly*	H205	Y	LG
Central gateway ECU	H202	L	LG
No. 5 CAN junction connector	H203	G	LG
Forward recognition camera*	H204	R	LG
Driving support ECU assembly*	H206	B	LG

*: w/ Lexus Safety System +

Text in Illustration
*a	Component without harness connected (No. 5 CAN Junction Connector)	-	-

Wiring Color
CAN Junction Connector RH1 Side	Code	Color (CANH Side)	Color (CANL Side)
Blind spot monitor sensor LH*	U26	V	LG
No. 2 CAN junction terminal	U28	Y	LG
No. 4 CAN junction connector	U25	G	LG

*: w/ Blind Spot Monitor System

Note

Do not reconnect the disconnected connectors until this inspection is complete because there may be a short to GND in 2 or more CAN bus lines.

Result

Symptom	Proceed to
The resistance between terminals 15 (CA5H) and 10 (GND), or the resistance between 16 (CA5L) and 10 (GND) is still below 200 Ω when all the specified connectors are disconnected from the CAN junction connector. (There is a short to GND in the CAN main bus lines between the No. 4 CAN junction connector and No. 5 CAN junction connector.)	A
The resistance between terminals 15 (CA5H) and 10 (GND), or the resistance between 16 (CA5L) and 10 (GND) becomes normal (200 Ω or higher) when a connector is disconnected from the CAN junction connector. (There is a short to GND in one of the areas that relate to the disconnected bus lines.)	B

When there is a short to GND in one or more of the bus lines that connect to an ECU or sensor:
1. Reconnect all of the connectors to the CAN junction connector, except for the one that was disconnected last (the bus line that is shorted to GND). Check that the resistance shown on the tester is normal (200 Ω or higher) to confirm that there is a short to GND in the one branch line only.

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

CHECK FOR SHORT TO GND IN CAN BUS LINE (NO. 2 CAN JUNCTION TERMINAL)

Reconnect all of the connectors to the No. 4 CAN junction connector and No. 5 CAN junction connector.

Disconnect the U28 No. 5 CAN junction connector.

Tech Tips

Connectors that connect to the CAN junction connector can be distinguished by the color of their CAN bus lines.
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.

Text in Illustration
*a	Rear view of wire harness connector (to No. 5 CAN Junction Connector)	*b	to No. 2 CAN Junction Terminal

Text in Illustration
*a	Component with harness connected (Central Gateway ECU)

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

Standard Resistance

Tester Connection	Condition	Specified Condition
H193-15 (CA5H) - H193-10 (GND)	Cable disconnected from negative (-) battery terminal	200 Ω or higher
H193-16 (CA5L) - H193-10 (GND)	Cable disconnected from negative (-) battery terminal	200 Ω or higher

Result

Symptom	Proceed to
The resistance between terminals 15 (CA5H) and 10 (GND), or the resistance between 16 (CA5L) and 10 (GND) is still below 200 Ω when a connector is disconnected from the No. 5 CAN junction connector.	A
The resistance between terminals 15 (CA5H) and 10 (GND), or the resistance between 16 (CA5L) and 10 (GND) becomes normal (200 kΩ or higher) when a connector is disconnected from the No. 5 CAN junction connector.	B

CHECK FOR SHORT TO GND IN CAN BUS LINE (NO. 2 CAN JUNCTION TERMINAL - NO. 5 CAN J/C) Click here

CHECK FOR SHORT TO GND IN CAN BUS LINE (NO. 4 CAN J/C)

Reconnect the U28 No. 5 CAN junction connector.

Disconnect the H203 No. 4 CAN junction connector.

Tech Tips

Connectors that connect to the CAN junction connector can be distinguished by the color of their CAN bus lines.
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.

Text in Illustration
*a	Rear view of wire harness connector (to No. 4 CAN Junction Connector)	*b	to No. 5 CAN Junction Connector

Text in Illustration
*a	Component with harness connected (Central Gateway ECU)

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

Standard Resistance

Tester Connection	Condition	Specified Condition
H193-15 (CA5H) - H193-10 (GND)	Cable disconnected from negative (-) battery terminal	200 Ω or higher
H193-16 (CA5L) - H193-10 (GND)	Cable disconnected from negative (-) battery terminal	200 Ω or higher

REPLACE NO. 4 CAN JUNCTION CONNECTOR

CHECK FOR SHORT TO GND IN CAN BUS LINE (NO. 4 CAN J/C - NO. 5 CAN J/C)

Reconnect the H203 No. 4 CAN junction connector.

Disconnect the U25 No. 5 CAN junction connector.

Tech Tips

Connectors that connect to the CAN junction connector can be distinguished by the color of their CAN bus lines.
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.

Text in Illustration
*a	Rear view of wire harness connector (to No. 5 CAN Junction Connector)	*b	to No. 4 CAN Junction Connector

Text in Illustration
*a	Component with harness connected (Central Gateway ECU)

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

Standard Resistance

Tester Connection	Condition	Specified Condition
H193-15 (CA5H) - H193-10 (GND)	Cable disconnected from negative (-) battery terminal	200 Ω or higher
H193-16 (CA5L) - H193-10 (GND)	Cable disconnected from negative (-) battery terminal	200 Ω or higher

REPLACE NO. 5 CAN JUNCTION CONNECTOR

REPAIR OR REPLACE CAN MAIN BUS LINE (NO. 4 CAN J/C - NO. 5 CAN J/C)

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

Reconnect the connector of the branch line that is shorted to GND to the CAN junction connector (the connector that caused the bus line resistance to change to 200 Ω or higher when it was disconnected).
Disconnect the connector that includes terminals CANH and CANL from the ECU or sensor to which the bus line shorted to GND is connected Click here.

Text in Illustration
*a	Component with harness connected (Central Gateway ECU)

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

Standard Resistance

Tester Connection	Condition	Specified Condition
H193-15 (CA5H) - H193-10 (GND)	Cable disconnected from negative (-) battery terminal	200 Ω or higher
H193-16 (CA5L) - H193-10 (GND)	Cable disconnected from negative (-) battery terminal	200 Ω or higher

Tech Tips

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.

REPLACE CORRESPONDING ECU OR SENSOR

REPAIR OR REPLACE CORRESPONDING ECU OR SENSOR BRANCH LINE OR CONNECTOR

CHECK FOR SHORT TO GND IN CAN BUS LINE (NO. 2 CAN JUNCTION TERMINAL - NO. 5 CAN J/C)

Reconnect the U28 No. 5 CAN junction connector
Disconnect the U19 No. 2 CAN junction terminal.

Text in Illustration
*a	Component with harness connected (Central Gateway ECU)

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

Standard Resistance

Tester Connection	Condition	Specified Condition
H193-15 (CA5H) - H193-10 (GND)	Cable disconnected from negative (-) battery terminal	200 Ω or higher
H193-16 (CA5L) - H193-10 (GND)	Cable disconnected from negative (-) battery terminal	200 Ω or higher

REPLACE NO. 2 CAN JUNCTION TERMINAL

REPAIR OR REPLACE CAN MAIN BUS LINE (NO. 2 CAN JUNCTION TERMINAL MAIN LINE)

CHECK FOR SHORT TO GND IN CAN BUS LINE (CENTRAL GATEWAY ECU - NO. 4 CAN J/C)

Reconnect the H202 No. 4 CAN junction connector.

Text in Illustration
*a	Front view of wire harness connector (to Central Gateway ECU)

Disconnect the H193 central gateway ECU connector.

Standard Resistance

Tester Connection	Condition	Specified Condition
H193-15 (CA5H) - H193-10 (GND)	Cable disconnected from negative (-) battery terminal	200 Ω or higher
H193-16 (CA5L) - H193-10 (GND)	Cable disconnected from negative (-) battery terminal	200 Ω or higher

REPLACE CENTRAL GATEWAY ECU Click here

REPAIR OR REPLACE CAN MAIN BUS LINE (CENTRAL GATEWAY ECU MAIN LINE)