Lexus NX: Electric Parking Brake ECU Communication Stop Mode

Lexus NX Service Manual / Power Source & Network / Networking / Can Communication System / Electric Parking Brake ECU Communication Stop Mode

DESCRIPTION

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

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 (PARKING BRAKE ECU ASSEMBLY BRANCH WIRE)

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

(b) Disconnect the parking brake ECU assembly connector.

*a	Front view of wire harness connector (to Parking Brake ECU Assembly)

Standard Resistance:

Tester Connection	Condition	Specified Condition
Q24-11 (CANH) - Q24-1 (CANL)	Cable disconnected from negative (-) auxiliary battery terminal	54 to 69 Ω

REPAIR OR REPLACE CAN BRANCH WIRE OR CONNECTOR

2.	CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT)

(a) Disconnect the parking brake ECU assembly connector.

*a	Front view of wire harness connector (to Parking Brake ECU Assembly)

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
Q25-9 (GND1) - 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	Switch Condition	Specified Condition
Q25-7 (+B) - Body ground	Power switch off	11 to 14 V
Q25-12(+B2) - Body ground	Power switch off	11 to 14 V
Q24-3(BECU) - Body ground	Power switch on (IG)	11 to 14 V
Q24-3(BECU) - Body ground	Power switch off	Below 1 V
Q24-5 (IG) - Body ground	Power switch on (IG)	11 to 14 V
Q24-5 (IG) - Body ground	Power switch off	Below 1 V

REPLACE PARKING BRAKE ECU ASSEMBLY

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)

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