Last Modified: 12-11-2024 6.11:8.1.0 Doc ID: RM100000002PY82
Model Year Start: 2025 Model: GR Corolla Prod Date Range: [09/2024 -           ]
Title: G16E-GTS (ENGINE CONTROL): SFI SYSTEM: ECM Power Source Circuit; 2025 MY GR Corolla [09/2024 -        ]

ECM Power Source Circuit

DESCRIPTION

When the ignition switch is turned on (IG), the battery voltage is applied to IGSW of the ECM. When the transistor in the MREL circuit operates, current flows from the battery to ground through the drive circuit of the EFI MAIN NO. 1 relay, thus operating the relay which supplies power to the +B and +B2 terminals of the ECM.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

Inspect the fuses for circuits related to this system before performing the following procedure.

PROCEDURE

1.

CHECK HARNESS AND CONNECTOR (ECM - BODY GROUND)

(a) Disconnect the ECM connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A139-10(E1) - Body ground

Always

Below 1 Ω
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

2.

CHECK TERMINAL VOLTAGE (IGP TERMINAL VOLTAGE)

(a) Disconnect the ECM connector.

(b) Turn the ignition switch to ON.

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

A139-2(IGP) - Body ground

Ignition switch ON

11 to 14 V

*a

Front view of wire harness connector

(to ECM)
NG

GO TO STEP 6

OK

3.

INSPECT EFI MAIN NO. 1 RELAY

Click here 2023 - 2025 MY GR Corolla [09/2022 -        ]; G16E-GTS (ENGINE CONTROL): RELAY: ON-VEHICLE INSPECTION

NG

REPLACE EFI MAIN NO. 1 RELAY
OK

4.

CHECK HARNESS AND CONNECTOR (EFI MAIN NO. 1 RELAY - ECM)

(a) Remove the EFI MAIN NO. 1 relay, EFI-MAIN NO. 2 relay, EFI-MAIN NO. 3 relay and EDU relay from the No. 1 engine room relay block and No. 1 junction block assembly.

HINT:

Remove the EFI MAIN NO. 1 relay, EFI-MAIN NO. 2 relay, EFI-MAIN NO. 3 relay and EDU relay connected between the checked terminals as the coil inside the relay influences the measurement value.

(b) Disconnect the ECM connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

1 (EFI MAIN NO. 1 relay) - A139-15 (MREL)

Always

Below 1 Ω

5 (EFI MAIN NO. 1 relay) - A139-9 (+B)

Always

Below 1 Ω

5 (EFI MAIN NO. 1 relay) - A139-35 (+B2)

Always

Below 1 Ω

1 (EFI MAIN NO. 1 relay) or A139-15 (MREL) - Body ground and other terminals

Always

10 kΩ or higher

5 (EFI MAIN NO. 1 relay), A139-9 (+B) or A139-35 (+B2) - Body ground and other terminals

Always

10 kΩ or higher
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

5.

CHECK TERMINAL VOLTAGE (POWER SOURCE OF EFI MAIN NO. 1 RELAY)

(a) Remove the EFI MAIN NO. 1 relay from the No. 1 engine room relay block and No. 1 junction block assembly.

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

3 (EFI MAIN NO. 1 relay) - Body ground

Always

11 to 14 V

2 (EFI MAIN NO. 1 relay) - Body ground

Always

11 to 14 V

*1

No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly

*2

EFI MAIN NO. 1 Relay
OK

REPLACE ECM

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - EFI MAIN NO. 1 RELAY)

6.

INSPECT NO. 1 INTEGRATION RELAY (IG2 NO.1 RELAY)

Click here 2023 - 2025 MY Corolla Corolla Hatchback Corolla HV GR Corolla [11/2022 -        ]; POWER DISTRIBUTION: INTEGRATION RELAY: INSPECTION

NG

REPLACE NO. 1 INTEGRATION RELAY
OK

7.

CHECK HARNESS AND CONNECTOR (NO. 1 INTEGRATION RELAY - ECM)

(a) Disconnect the No. 1 integration relay connector.

(b) Disconnect the ECM connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

9A-9 - A139-2(IGP)

Always

Below 1 Ω

9A-9 or A139-2(IGP) - Body ground and other terminals

Always

10 kΩ or higher
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

8.

CHECK HARNESS AND CONNECTOR (POWER SOURCE VOLTAGE OF NO. 1 INTEGRATION RELAY)

*a

Front view of wire harness connector

(to No. 1 Integration Relay)

(a) Disconnect the No. 1 integration relay connector.

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

9A-10 - Body ground

Always

11 to 14 V
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - NO. 1 INTEGRATION RELAY)
OK

9.

CHECK HARNESS AND CONNECTOR (NO. 1 INTEGRATION RELAY - BODY GROUND)

(a) Disconnect the No. 1 integration relay connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

9A-8 - Body ground

Always

Below 1 Ω
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

10.

CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU - NO. 1 INTEGRATION RELAY)

(a) Disconnect the certification ECU (smart key ECU assembly) connector.

(b) Disconnect the No. 1 integration relay connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

O175-22(IGPD) - 9A-7

Always

Below 1 Ω

O175-22(IGPD) or 9A-7 - Body ground and other terminals

Always

10 kΩ or higher
OK

GO TO SMART KEY SYSTEM (FOR START FUNCTION)

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR