Lexus NX: Bus Buffer ECU Communication Stop Mode

Lexus NX Service Manual / Power Source & Network / Networking / Can Communication System / Bus Buffer ECU Communication Stop Mode

DESCRIPTION

Detection Item	Symptom	Trouble Area
Bus Buffer ECU Communication Stop Mode	Any of the following conditions are met: Communication stop for "Accessory Gateway" is indicated on the "Communication Bus Check" screen of the Techstream. Click here Communication system DTCs (DTCs that start with U) that correspond to "Bus Buffer ECU Communication Stop Mode" in "DTC Combination Table" are output. Click here	Option connector (bus buffer ECU) branch wire or connector Option connector (bus buffer ECU)

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.

Click here
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 OPTIONS

(a) Check whether dealer installed options that support CAN communication are installed.

Result	Proceed to
Installed	A
Not installed	B

GO TO STEP 3

2.	CHECK FOR OPEN IN CAN BUS WIRE (OPTION CONNECTOR [BUS BUFFER ECU] BRANCH WIRE)

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

(b) Disconnect the option connector (bus buffer ECU).*

*: When a dealer-installed option is installed

*a	Front view of wire harness connector (to Option Connector [Bus Buffer ECU])

Standard Resistance:

Tester Connection	Condition	Specified Condition
I130-4 (CAN+) - I130-8 (CAN-)	Cable disconnected from negative (-) auxiliary battery terminal	54 to 69 Ω

CHECK DEALER-INSTALLED OPTION

REPAIR OR REPLACE CAN BRANCH WIRE OR CONNECTOR

3.	CHECK FOR DTC

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

*: When a dealer-installed option is installed

(d) Enter the following menus: Body Electrical / Central Gateway / Utility / Initialization.

Body Electrical > Central Gateway > Utility

Tester Display
Initialization

(e) Enter the following menus: Body Electrical / Main Body / Utility / Initialization.

Body Electrical > Main Body > Utility

Tester Display
Initialization

(f) Enter the following menus: Body Electrical / Main Body / Clear DTCs.

Body Electrical > Main Body > Clear DTCs

(g) Enter the following menus: Body Electrical / Main Body / Clear DTCs.

Body Electrical > Main Body > Trouble Codes

(h) Enter the following menus: Body Electrical / Main Body / Trouble Codes.

Body Electrical > Main Body > Trouble Codes

Result	Proceed to
DTC U1117 is not output from main body ECU (multiplex network body ECU)	A
DTC U1117 is output from main body ECU (multiplex network body ECU)	B

END

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

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