Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Back Door Closer Switch Malfunction (B2251)

DESCRIPTION

The multiplex network door ECU receives signals from the latch switch, position switch, pawl switch and back door courtesy switch, which are built into the back door lock assembly. Based on these signals, the latch position of the back door lock assembly is determined.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area
B2251	Back Door Closer Switch Malfunction	While the back door closer is operating, a malfunction in the position information from the back door courtesy switch is detected within a certain amount of time.	Back door lock assembly Multiplex network door ECU Wire harness or connector

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

If the multiplex network door ECU has been removed and installed or replaced, or if any of the connectors have been disconnected, initialize the power back door system.

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PROCEDURE

1.	READ VALUE USING TECHSTREAM

(a) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Back Door / Data List.

(e) Read the Data List according to the display on the Techstream.

Body Electrical > Back Door > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Half Latch SW	Half-latch switch signal	OFF or ON	OFF: Back door lock motor in full latch or half latch position ON: Back door lock motor in open latch position	-

Body Electrical > Back Door > Data List

Tester Display
Half Latch SW

OK:

The display is as specified in the normal condition column.

NG

GO TO STEP 3

OK

2.	READ VALUE USING TECHSTREAM

(a) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Back Door / Data List.

(e) Read the Data List according to the display on the Techstream.

Body Electrical > Back Door > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Courtesy SW	Latch courtesy switch signal	OFF or ON	OFF: Back door closed ON: Back door open	-

Body Electrical > Back Door > Data List

Tester Display
Courtesy SW

OK:

The display is as specified in the normal condition column.

OK

REPLACE MULTIPLEX NETWORK DOOR ECU

NG

3.	INSPECT BACK DOOR LOCK ASSEMBLY

(a) Remove the back door lock assembly.

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(b) Inspect the back door lock assembly.

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NG

REPLACE BACK DOOR LOCK ASSEMBLY

OK

4.	CHECK HARNESS AND CONNECTOR (BACK DOOR LOCK ASSEMBLY - MULTIPLEX NETWORK DOOR ECU AND BODY GROUND)

(a) Disconnect the Z16 multiplex network door ECU connector.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
Z7-3 (CLS) - Z16-9 (HAF)	Always	Below 1 Ω
Z7-8 (CTY) - Z16-11 (FUL)	Always	Below 1 Ω
Z7-7 (E) - Body ground	Always	Below 1 Ω
Z7-3 (CLS) or Z16-9 (HAF) - Body ground	Always	10 kΩ or higher
Z7-8 (CTY) or Z16-11 (FUL) - Body ground	Always	10 kΩ or higher

OK

REPLACE MULTIPLEX NETWORK DOOR ECU

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR