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.

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.
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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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Removal

REMOVAL PROCEDURE 1. REMOVE FRONT WHEEL RH Click here 2. REMOVE FRONT FENDER MOULDING SUB-ASSEMBLY RH HINT: Use the same procedure described for the LH side. Click here 3. REMOVE NO. 1 MOULDING TAPE HINT: Use the same procedure described for the LH side. Click here 4. REMOVE NO. 2 MOULDING TAP

Removal

REMOVAL PROCEDURE 1. REMOVE NO. 1 ENGINE UNDER COVER ASSEMBLY Click here 2. REMOVE INVERTER WITH CONVERTER ASSEMBLY Click here 3. REMOVE INVERTER WATER PUMP WITH MOTOR ASSEMBLY Click here 4. REMOVE INVERTER BRACKET ASSEMBLY Click here 5. DISCONNECT WIRE HARNESS (a) Disconnect the 4

Lexus NX: ECM Communication Stop Mode

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Main Body ECU Communication Stop Mode

Combination Meter ECU Communication Stop Mode

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Removal

Removal