IG Signal Circuit [01/2019 - 09/2022]: Procedure

WARNING: This page is about a different car, the 2022 Toyota Corolla, 2021 Toyota Corolla, 2020 Toyota Corolla, and 2019 Toyota Corolla. However, it is still accessible from the selected car via links, so may be relevant.

READ VALUE USING TECHSTREAM

Connect the Techstream to the DLC3.
Turn the ignition switch to ON.
Turn the Techstream on.
Enter the following menus: Body Electrical / Main Body / Data List.

Read the Data List according to the display on the Techstream.

Body Electrical > Main Body > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
IG SW	Ignition switch ON signal	OFF or ON	OFF: Ignition switch off ON: Ignition switch ON	"OFF" is also displayed for this item when the ignition switch is ACC.

Body Electrical > Main Body > Data List

Tester Display
IG SW

Normal conditions listed above are displayed.

Result

Proceed to
OK
NG

Result:

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to PROBLEM SYMPTOMS TABLE [01/2019 - 09/2022]

Result:

See step 2

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

Disconnect the 4D and 4F instrument panel junction block assembly connectors.

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

Standard Voltage

Tester Connection	Condition	Specified Condition
4D-1 - Body ground	Always	11 to 14 V

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

Standard Resistance

Tester Connection	Condition	Specified Condition
4F-3 - Body ground	Always	Below 1 Ω

Result

Proceed to
OK
NG

Result:

REPAIR OR REPLACE HARNESS OR CONNECTOR

Result:

See step 3

CHECK HARNESS AND CONNECTOR (MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU) - BODY GROUND)

Disconnect the I86 main body ECU (multiplex network body ECU) connector.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
I86-19 (GND2) - Body ground	Always	Below 1 Ω

Result

Proceed to
OK
NG

Result:

REPAIR OR REPLACE HARNESS OR CONNECTOR

Result:

See step 4

CHECK HARNESS AND CONNECTOR (IG1-NO. 1 RELAY POWER SOURCE)

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Component with harness connected
(Instrument Panel Junction Block Assembly)

Connect the 4D and 4F instrument panel junction block assembly connectors.
Connect the I86 main body ECU (multiplex network body ECU) connector.

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

Standard Voltage

Tester Connection	Condition	Specified Condition
4E-17 - Body ground	Ignition switch ON	11 to 14 V

Result

Proceed to
OK
NG

Result:

REPAIR OR REPLACE HARNESS OR CONNECTOR

Result:

See step 5

INSPECT INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY

Component without harness connected
(Instrument Panel Junction Block Assembly)

Remove the main body ECU (multiplex network body ECU) from the instrument panel junction block assembly.
Refer to REMOVAL [01/2019 - 03/2019] , or refer to REMOVAL [03/2019 - 09/2022]

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

Standard Resistance

Tester Connection	Condition	Specified Condition
4F-3 - MB-11 (GND1)	Always	Below 1 Ω
4D-1 - MB-32 (IG)	Battery not connected to 4E-17 and 4F-3	10 kΩ or higher
4D-1 - MB-32 (IG)	Battery positive (+) → 4E-17 Battery negative (-) → 4F-3	Below 1 Ω

Result

Proceed to
OK
NG

Result:

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU). Refer to REMOVAL [01/2019 - 03/2019] , or refer to REMOVAL [03/2019 - 09/2022]

Result:

REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY. Refer to REMOVAL [01/2019 - 03/2019] , or refer to REMOVAL [03/2019 - 09/2022]