Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Extension Module Disconnected 2 (B1543)

DESCRIPTION

If the radio receiver assembly cannot detect the navigation ECU for a certain period of time (90 seconds) after the engine switch is turned on (ACC) and the radio receiver assembly confirms that the information is missing by checking past navigation ECU recognition information (registered information), this DTC will be stored.

HINT:

The Navigation system uses USB communication between devices. If an open, short, short to +B or short to ground occurs in the USB circuit, communication is interrupted and the Navigation system will not operate normally.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area
B1543	Extension Module Disconnected 2	Navigation ECU disconnected	Navigation ECU Radio receiver assembly No. 1 navigation wire Harness or connector

HINT:

This DTC may be stored due to environmental reasons such as electrical noise or interference.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

PROCEDURE

1.	CHECK MAP SCREEN

(a) Turn the engine switch on (ACC) and wait for 90 seconds.

(b) Press the "MAP" switch and check that the map screen is displayed normally.

Result	Proceed to
Map screen is displayed normally	A
Map screen is not displayed normally	B

A

USE SIMULATION METHOD TO CHECK

B

2.

CHECK DTC

(a) Clear the DTCs.

Body Electrical > Navigation System > Clear DTCs

(b) Turn the engine switch off.

(c) Turn the engine switch on (IG) and wait for 90 seconds.

(d) Recheck for DTCs and check that no DTCs are output.

Body Electrical > Navigation System > Trouble Codes

OK:

No DTCs are output.

OK

USE SIMULATION METHOD TO CHECK

NG

3.	CHECK HARNESS AND CONNECTOR (NAVIGATION ECU POWER SOURCE)

(a) Disconnect the J153 navigation ECU connector.

*a Front view of wire harness connector (to Navigation ECU)

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
J153-23 (GND) - Body ground	Always	Below 1 Ω

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
J153-10 (+B) - Body ground	Always	11 to 14 V

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

4.	CHECK NO. 1 NAVIGATION WIRE (RADIO RECEIVER ASSEMBLY - NAVIGATION ECU)

(a) Disconnect the z31 radio receiver assembly connector.

*a Front view of wire harness connector (to Navigation ECU) *b Front view of wire harness connector (to Radio Receiver Assembly)

(b) Disconnect the z32 navigation ECU connector.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
z31-4 (US4+) - z32-4 (US4+)	Always	Below 1 Ω
z31-5 (US4-) - z32-5 (US4-)	Always	Below 1 Ω
z31-6 (UGD4) - z32-6 (UGD4)	Always	Below 1 Ω

NG

REPLACE NO. 1 NAVIGATION WIRE

OK

5.	REPLACE NAVIGATION ECU

(a) Replace the navigation ECU with a new or known good one.

Click here

NEXT

6.

CHECK DTC

(a) Clear the DTCs.

Body Electrical > Navigation System > Clear DTCs

(b) Turn the engine switch off.

(c) Turn the engine switch on (IG) and wait for 90 seconds.

(d) Recheck for DTCs and check that no DTCs are output.

Body Electrical > Navigation System > Trouble Codes

OK:

No DTCs are output.

OK

END (NAVIGATION ECU IS DEFECTIVE)

NG

REPLACE RADIO RECEIVER ASSEMBLY