Lexus NX: ECM Communication Stop Mode

Lexus NX Service Manual / Power Source & Network / Networking / Can Communication System / ECM Communication Stop Mode

DESCRIPTION

Detection Item	Symptom	Trouble Area
ECM Communication Stop Mode	Any of the following conditions are met: Communication stop for "Engine" is indicated on the "Communication Bus Check" screen of the Techstream. Click here Communication system DTCs (DTCs that start with U) that correspond to "ECM Communication Stop Mode" in "DTC Combination Table" are output. Click here	ECM main wire or connector Power source circuit of ECM ECM ground circuit ECM

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.
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When disconnecting and reconnecting the auxiliary battery.
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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.
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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 OPEN IN CAN BUS WIRE (ECM MAIN WIRE)

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

(b) Disconnect the ECM connector.

*a	Front view of wire harness connector (to ECM)

Standard Resistance:

Tester Connection	Condition	Specified Condition
A35-13 (CANH) - A35-26 (CANL)	Cable disconnected from negative (-) auxiliary battery terminal	108 to 132 Ω

REPAIR OR REPLACE CAN MAIN WIRE OR CONNECTOR

2.	CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT)

(a) Disconnect the ECM connector.

Front view of wire harness connector

(to ECM)

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
C48-16 (E1) - Body ground	Cable disconnected from negative (-) auxiliary battery terminal	Below 1 Ω
C48-49 (E02) - Body ground	Cable disconnected from negative (-) auxiliary battery terminal	Below 1 Ω
C48-50 (E01) - Body ground	Cable disconnected from negative (-) auxiliary battery terminal	Below 1 Ω
C48-58 (ME01) - Body ground	Cable disconnected from negative (-) auxiliary battery terminal	Below 1 Ω
C48-53 (E04) - Body ground	Cable disconnected from negative (-) auxiliary battery terminal	Below 1 Ω

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
A35-1 (BATT) - Body ground	Power switch off	11 to 14 V
A35-2 (+B) - Body ground	Auxiliary battery voltage applied to terminal A35-46 (MREL)	11 to 14 V
A35-3 (+B2) - Body ground	Auxiliary battery voltage applied to terminal A35-46 (MREL)	11 to 14 V
A35-37 (IGSW) - Body ground	Power switch on (IG)	11 to 14 V
A35-37 (IGSW) - Body ground	Power switch off	Below 1 V

REPLACE ECM

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)

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Fail-safe Chart

FAIL-SAFE CHART FAIL-SAFE FUNCTION (a) When a malfunction occurs in the pre-collision system, a message will be displayed on the multi-information display and the pre-collision system will be disabled depending on the malfunction. Warning Message Cause DTC/RoB Conditions to Return to Normal

Light bulbs

You may replace the following bulbs by yourself. The difficulty level of replacement varies depending on the bulb. If necessary bulb replacement seems difficult to perform, contact your Lexus dealer. For more information about replacing other light bulbs, contact your Lexus dealer. Bul

Lexus NX: ECM Communication Stop Mode

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Fail-safe Chart

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