Last Modified: 05-13-2024 6.11:8.1.0 Doc ID: RM1000000028ELA
Model Year Start: 2023 Model: Corolla Hatchback Prod Date Range: [11/2022 -           ]
Title: K120 / K121 (CVT): K120 CONTINUOUSLY VARIABLE TRANSAXLE SYSTEM: ECU Power Source Circuit; 2023 - 2025 MY Corolla Corolla Hatchback [11/2022 -        ]

ECU Power Source Circuit

DESCRIPTION

When the engine switch is turned on (IG), battery voltage is applied to terminal MREL of the ECM through the coil of the EFI-MAIN NO. 1 relay. This causes the EFI-MAIN NO. 1 relay to close, which supplies power to terminal +B of the TCM.

WIRING DIAGRAM

Refer to DTC U010087.

Click here 2023 - 2025 MY Corolla Corolla Hatchback [11/2022 -        ]; K120 / K121 (CVT): K120 CONTINUOUSLY VARIABLE TRANSAXLE SYSTEM: U010087; Lost Communication with ECM/PCM "A" Missing Message

CAUTION / NOTICE / HINT

NOTICE:

  • Inspect the fuses for circuits related to this system before performing the following procedure.
  • Perform registration and/or initialization when parts related to the continuously variable transaxle system are replaced.

    Click here 2023 - 2025 MY Corolla Corolla Hatchback [11/2022 -        ]; K120 / K121 (CVT): K120 CONTINUOUSLY VARIABLE TRANSAXLE SYSTEM: PRECAUTION

PROCEDURE

1.

CHECK HARNESS AND CONNECTOR (TCM - BODY GROUND)

(a) Disconnect the C80 TCM connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

C80-2 (E1) - Body ground

Always

Below 1 Ω

(c) Connect the C80 TCM connector.

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

2.

INSPECT ECU TERMINAL VOLTAGE (+B TERMINAL)

(a) Disconnect the C80 TCM connector.

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

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

C80-1 (+B) - Body ground

Engine switch on (IG)

11 to 14 V

(d) Connect the C80 TCM connector.

Result

Proceed to

OK

A

NG

B

A

CHECK FOR INTERMITTENT PROBLEMS

B

3.

CHECK HARNESS AND CONNECTOR (TCM - 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) Disconnect the C80 TCM connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

C80-1 (+B) - 3 (EFI-MAIN NO. 1 relay)

Always

Below 1 Ω

C80-1 (+B) or 3 (EFI-MAIN NO. 1 relay) - Body ground

Always

10 kΩ or higher

(d) Connect the C80 TCM connector.

(e) Install the EFI-MAIN NO. 1 relay to the No. 1 engine room relay block and No. 1 junction block assembly.

OK

GO TO ECM POWER SOURCE CIRCUIT (ENGINE CONTROL SYSTEM / SFI SYSTEM) 2023 MY Corolla Corolla Hatchback [11/2022 - 03/2023]; M20A-FKS (ENGINE CONTROL): SFI SYSTEM: ECM Power Source Circuit 2023 - 2025 MY Corolla Corolla Hatchback [03/2023 -        ]; M20A-FKS (ENGINE CONTROL): SFI SYSTEM: ECM Power Source Circuit

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR