Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

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HOMESERVICE MANUALSTOYOTA20184RUNNER SR5, 4WDREPAIR AND DIAGNOSISENGINE PERFORMANCEENGINE CONTROL SYSTEMSENGINE CONTROL SYSTEM - SERVICE INFORMATIONRELAYON-VEHICLE INSPECTION [08/2015 - 08/2019]PROCEDURE

2018 Toyota 4Runner SR5, 4WD

On-Vehicle Inspection [08/2015 - 08/2019]: Procedure

2018 Toyota 4Runner SR5, 4WDSECTION Procedure

INSPECT NO. 1 INTEGRATION RELAY (IG2)

Check the IG2 fuse.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
IG2 fuse	Always	Below 1 Ω

If the result is not as specified, replace the IG2 fuse.

Check the IG2 relay.

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

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Standard Resistance

Tester Connection	Condition	Specified Condition
1E-1 - 1C-4	Battery voltage not applied to terminals 1C-1 and 1C-3	10 kΩ or higher
1E-1 - 1C-4	Battery voltage applied to terminals 1C-1 and 1C-3	Below 1 Ω

TEXT IN ILLUSTRATION

*a	Component without harness connected (No. 1 Integration Relay)

If the result is not as specified, replace the No. 1 integration relay.

INSPECT NO. 1 INTEGRATION RELAY (EFI)

Check the EFI fuse.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
EFI fuse	Always	Below 1 Ω

If the result is not as specified, replace the EFI fuse.

Check the EFI relay.

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

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Standard Resistance

Tester Connection	Condition	Specified Condition
1E-1 - 1D-4	Battery voltage not applied to terminals 1D-2 and 1D-3	10 kΩ or higher
1E-1 - 1D-4	Battery voltage applied to terminals 1D-2 and 1D-3	Below 1 Ω

TEXT IN ILLUSTRATION

*a	Component without harness connected (No. 1 Integration Relay)

If the result is not as specified, replace the No. 1 integration relay.

INSPECT NO. 1 INTEGRATION RELAY (A/F)

Check the A/F fuse.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
A/F fuse	Always	Below 1 Ω

If the result is not as specified, replace the A/F fuse.

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

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Standard Resistance

Tester Connection	Condition	Specified Condition
1E-1 - 1D-8	Battery voltage not applied to terminals 1D-4 and 1D-7	10 kΩ or higher
1E-1 - 1D-8	Battery voltage applied to terminals 1D-4 and 1D-7	Below 1 Ω

TEXT IN ILLUSTRATION

*a	Component without harness connected (No. 1 Integration Relay)

If the result is not as specified, replace the No. 1 integration relay.

INSPECT AIR PUMP HEATER RELAY (AIR PUMP HTR)

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

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Standard Resistance

Tester Connection	Condition	Specified Condition
3 - 5	Battery voltage is not applied to terminals 1 and 2	10 kΩ or higher
3 - 5	Battery voltage is applied to terminals 1 and 2	Below 1 Ω

If the result is not as specified, replace the air pump heater relay.

INSPECT AIR INJECTION VSV RELAY (AI-VSV)

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

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Standard Resistance

Tester Connection	Condition	Specified Condition
3 - 5	Battery voltage is not applied to terminals 1 and 2	10 kΩ or higher
3 - 5	Battery voltage is applied to terminals 1 and 2	Below 1 Ω

If the result is not as specified, replace the air injection VSV relay.

INSPECT MAIN BODY ECU (DRIVER SIDE JUNCTION BLOCK)

NOTE:

The ACC relay and IG1 No. 1 relay are built into the main body ECU (driver side junction block).

Inspect the ACC relay.

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

TEXT IN ILLUSTRATION

Component without harness connected
(Main Body ECU)

Standard Resistance

Tester Connection	Condition	Specified Condition
2B-17 - 2E-1	Battery voltage not applied to terminals 2C-48 and 2B-4	10 kΩ or higher
2B-17 - 2E-1	Battery voltage applied to terminals 2C-48 and 2B-4	Below 1 Ω

If the result is not as specified, replace the main body ECU.

Inspect the IG1 No. 1 relay.

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

TEXT IN ILLUSTRATION

Component without harness connected
(Main Body ECU)

Standard Resistance

Tester Connection	Condition	Specified Condition
2C-31 - 2E-1	Battery voltage not applied to terminals 2C-52 and 2B-4	10 kΩ or higher
2C-31 - 2E-1	Battery voltage applied to terminals 2C-52 and 2B-4	Below 1 Ω

If the result is not as specified, replace the main body ECU.

RENDER: 1.0x

NO RELATED

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.