| Last Modified: 06-05-2026 | 6.11:8.1.0 | Doc ID: RM1000000028ELA |
| Model Year Start: 2023 | Model: Corolla | Prod Date Range: [11/2022 - 09/2024] |
| Title: K120 / K121 (CVT): K120 CONTINUOUSLY VARIABLE TRANSAXLE SYSTEM: ECU Power Source Circuit; 2023 - 2025 MY Corolla Corolla Hatchback [11/2022 - 09/2024] | ||
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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.
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![2023 - 2025 MY Corolla Corolla Hatchback [11/2022 - 09/2024]; K120 / K121 (CVT): K120 CONTINUOUSLY VARIABLE TRANSAXLE SYSTEM: U010087; Lost Communication with ECM/PCM "A" Missing Message](/t3Portal/stylegraphics/info.gif)
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.
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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 |
|
|
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
|
Result |
Proceed to |
|---|---|
|
OK |
A |
|
NG |
B |
| A |
|
|
|
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.
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