Lexus NX: IG Signal Circuit

DESCRIPTION

This circuit detects whether the power switch is on (IG) or off, and sends this information to the main body ECU (multiplex network body ECU).

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • Inspect the fuses for circuits related to this system before performing the following procedure.
  • Recognition code registration is necessary when replacing the main body ECU (multiplex network body ECU).
  • If the main body ECU (multiplex network body ECU) is replaced, refer to Registration.

PROCEDURE

1.

READ VALUE USING TECHSTREAM (IG SW)

(a) Using the Techstream, read the Data List.

Click here

Body Electrical > Main Body > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

IG SW

Power switch on (IG) signal

ON or OFF

ON: Power switch on (IG)

OFF: Power switch off

"OFF" is also displayed for this item when the power switch is on (ACC).

Body Electrical > Main Body > Data List

Tester Display

IG SW

OK:

The display is as specified in the normal condition column.

OK

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

NG

2.

CHECK HARNESS AND CONNECTOR (INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY - BATTERY AND BODY GROUND)

(a) Disconnect the instrument panel junction block assembly connectors.

*a

Front view of wire harness connector

(to Instrument Panel Junction Block Assembly)

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

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

4F-1 - Body ground

Power switch off

11 to 14 V

4C-44 - Body ground

Power switch on (IG)

11 to 14 V

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

4D-9 - Body ground

Always

Below 1 Ω

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

3.

CHECK HARNESS AND CONNECTOR (INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY CIRCUIT)

(a) Disconnect the 4C and 4D instrument panel junction block assembly connectors.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

4C-41 - 4D-43

Always

Below 1 Ω

4C-41 or 4D-43 - Body ground

Always

10 kΩ or higher

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

4.

INSPECT INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY

(a) Remove the instrument panel junction block assembly.

Click here

*a

Component without harness connected

(Instrument Panel Junction Block Assembly)

(b) Remove the main body ECU (multiplex network body ECU) from the instrument panel junction block assembly.

Click here

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A-32 (IG) - 4D-43

Always

Below 1 Ω

4F-1 - 4C-41

Not connected

10 kΩ or higher

4F-1 - 4C-41

Battery positive (+) → 4C-44

Battery negative (-) → 4D-9

Below 1 Ω

OK

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

NG

REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY

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