Lexus NX manuals

Lexus NX: Check Bus 5 Lines for Short Circuit

Lexus NX Service 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 CAN main bus lines and/or CAN branch lines when the resistance between terminals 15 (CA5H) and 16 (CA5L) of the central gateway ECU (network gateway ECU) is below 54 Ω.

Symptom

Trouble Area
*1: w/ Pre-collision System

*2: w/ Intuitive Parking Assist System

*3: w/ Panoramic View Monitor System

*4: w/ Blind Spot Monitor System

*5: w/ Adaptive Variable Suspension System

Resistance between terminals 15 (CA5H) and 16 (CA5L) of central gateway ECU (network gateway ECU) is below 54 Ω.
  • Short in CAN main bus wire
  • Short in CAN branch wire
  • Forward recognition camera*1
  • Clearance warning ECU assembly*2
  • Millimeter wave radar sensor assembly*1
  • Central gateway ECU (network gateway ECU)
  • Parking assist ECU*3
  • Blind spot monitor sensor LH*4
  • Rear television camera assembly
  • Hybrid vehicle control ECU
  • Absorber control ECU*5
  • Vehicle approaching speaker controller
  • No. 4 CAN junction connector
  • No. 7 CAN junction connector

WIRING DIAGRAM

CAUTION / NOTICE / HINT

CAUTION:

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

NOTICE:

  • Inspect the fuses for circuits related to this system before performing the following procedure.
  • Before measuring the resistance of the CAN bus, turn the power 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 (-) auxiliary battery terminal and leave the vehicle for 1 minute or more before measuring the resistance.
  • After turning the power switch off, waiting time may be required before disconnecting the cable from the negative (-) auxiliary battery terminal.

    Click here

  • When disconnecting and reconnecting the auxiliary battery.

    Click here

    HINT:

    When disconnecting and reconnecting the auxiliary battery, there is an automatic learning function that completes learning when the respective system is used.

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  • Some parts must be initialized and set when replacing or removing and installing parts.

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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: Turn the power 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 as normal.

    Click here

HINT:

  • Operating the power switch, any switches or any doors triggers related ECU and sensor communication with the CAN, which causes resistance variation.
  • 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 WIRES (NO. 4 CAN JUNCTION CONNECTOR)

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

(b) Disconnect the No. 4 CAN junction connector.

*a

Front view of wire harness connector

(to No. 4 CAN Junction Connector)

*b

to Vehicle Approaching Speaker Controller

*c

to Central Gateway ECU (Network Gateway ECU)

*d

to Millimeter Wave Radar Sensor Assembly (w/ Pre-collision System)

*e

to Clearance Warning ECU Assembly (w/ Intuitive Parking Assist System)

*f

to Forward Recognition Camera (w/ Pre-collision System)

*g

to No. 7 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/ Pre-collision System

*2: w/ Intuitive Parking Assist System

I95-2 (CANH) - I95-12 (CANL)

Cable disconnected from negative (-) auxiliary battery terminal

200 Ω or higher

Vehicle approaching speaker controller

I95-3 (CANH) - I95-13 (CANL)

Cable disconnected from negative (-) auxiliary battery terminal

108 to 132 Ω

Central gateway ECU (network gateway ECU)

I95-4 (CANH) - I95-14 (CANL)

Cable disconnected from negative (-) auxiliary battery terminal

200 Ω or higher

Millimeter wave radar sensor assembly*1

I95-6 (CANH) - I95-16 (CANL)

Cable disconnected from negative (-) auxiliary battery terminal

200 Ω or higher

Clearance warning ECU assembly*2

I95-8 (CANH) - I95-18 (CANL)

Cable disconnected from negative (-) auxiliary battery terminal

200 Ω or higher

Forward recognition camera*1

I95-9 (CANH) - I95-19 (CANL)

Cable disconnected from negative (-) auxiliary battery terminal

108 to 132 Ω

No. 7 CAN junction connector

Result

Proceed to

OK

A

NG (No. 7 CAN junction connector CAN main wire)

B

NG (Central gateway ECU [network gateway ECU] CAN main wire)

C

NG (Wire to ECU or sensor)

D
A

REPLACE NO. 4 CAN JUNCTION CONNECTOR
C

GO TO STEP 6

D

GO TO STEP 8

B

2.

CONNECT CONNECTOR

(a) Reconnect the I95 No. 4 CAN junction connector.

NEXT

3.

CHECK FOR SHORT IN CAN BUS WIRES (NO. 7 CAN JUNCTION CONNECTOR)

(a) Disconnect the No. 7 CAN junction connector.

*a

Front view of wire harness connector

(to No. 7 CAN Junction Connector)

*b

to Parking Assist ECU (w/ Panoramic View Monitor System)

*c

to Blind Spot Monitor Sensor LH (w/ Blind Spot Monitor System)

*d

to Hybrid Vehicle Control ECU

*e

to No. 4 CAN Junction Connector

*f

to Absorber Control ECU (w/ Adaptive Variable Suspension System)

*g

to Rear Television Camera Assembly

-

-

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

Connected to
*1: w/ Panoramic View Monitor System

*2: w/ Blind Spot Monitor System

*3: w/ Adaptive Variable Suspension System

Q32-2 (CANH) - Q32-12 (CANL)

Cable disconnected from negative (-) auxiliary battery terminal

200 Ω or higher

Parking assist ECU*1

Q32-3 (CANH) - Q32-13 (CANL)

Cable disconnected from negative (-) auxiliary battery terminal

200 Ω or higher

Blind spot monitor sensor LH*2

Q32-4 (CANH) - Q32-14 (CANL)

Cable disconnected from negative (-) auxiliary battery terminal

108 to 132 Ω

Hybrid vehicle control ECU

Q32-5 (CANH) - Q32-15 (CANL)

Cable disconnected from negative (-) auxiliary battery terminal

200 Ω or higher

No. 4 CAN junction connector

Q32-7 (CANH) - Q32-17 (CANL)

Cable disconnected from negative (-) auxiliary battery terminal

200 Ω or higher

Absorber control ECU*3

Q32-8 (CANH) - Q32-18 (CANL)

Cable disconnected from negative (-) auxiliary battery terminal

200 Ω or higher

Rear television camera assembly

Result

Proceed to

OK

A

NG (Hybrid vehicle control ECU CAN main wire)

B

NG (No. 4 CAN junction connector CAN main wire)

C

NG (Wire to ECU or sensor)

D
A

REPLACE NO. 7 CAN JUNCTION CONNECTOR
C

REPAIR OR REPLACE CAN MAIN WIRE OR CONNECTOR (NO. 7 CAN JUNCTION CONNECTOR - NO. 4 CAN JUNCTION CONNECTOR)
D

GO TO STEP 8

B

4.

CONNECT CONNECTOR

(a) Reconnect the Q32 No. 7 CAN junction connector.

NEXT

5.

CHECK FOR SHORT IN CAN BUS WIRES (HYBRID VEHICLE CONTROL ECU - NO. 7 CAN JUNCTION CONNECTOR)

(a) Disconnect the hybrid vehicle control ECU connector.

*a

Front view of wire harness connector

(to Hybrid Vehicle Control ECU)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

I115-34(CA2H) - I115-35(CA2L)

Cable disconnected from negative (-) auxiliary battery terminal

108 to 132 Ω
OK

REPLACE HYBRID VEHICLE CONTROL ECU

NG

REPAIR OR REPLACE CAN MAIN WIRE OR CONNECTOR (HYBRID VEHICLE CONTROL ECU - NO. 7 CAN JUNCTION CONNECTOR)

6.

CONNECT CONNECTOR

(a) Reconnect the I95 No. 4 CAN junction connector.

NEXT

7.

CHECK FOR SHORT IN CAN BUS WIRES (CENTRAL GATEWAY ECU [NETWORK GATEWAY ECU] - NO. 4 CAN JUNCTION CONNECTOR)

(a) Disconnect the central gateway ECU (network gateway ECU) connector.

*a

Front view of wire harness connector

(to Central Gateway ECU [Network Gateway ECU])

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

I160-15 (CA5H) - I160-16 (CA5L)

Cable disconnected from negative (-) auxiliary battery terminal

108 to 132 Ω
OK

REPLACE CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU)

NG

REPAIR OR REPLACE CAN MAIN WIRE OR CONNECTOR (CENTRAL GATEWAY ECU [NETWORK GATEWAY ECU] - NO. 4 CAN JUNCTION CONNECTOR)

8.

CHECK FOR SHORT IN CAN BUS WIRES (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

I160-15 (CA5H) - I160-16 (CA5L)

Cable disconnected from negative (-) auxiliary 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

(Central Gateway ECU [Network Gateway ECU])
OK

REPLACE ECU OR SENSOR
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

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