Toyota Corolla Cross Owners & Service Manuals

Toyota Corolla Cross: ECU Power Source Circuit

Toyota Corolla Cross (2022-2024) Service Manual / Engine & Hybrid System / Hybrid / Battery Control / Hybrid Control System / ECU Power Source Circuit

DESCRIPTION

If the ignition switch is ON, the hybrid vehicle control ECU applies current to the MREL terminal to turn the IGCT relay on. This supplies power to the +B1 terminal.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • After the ignition switch is turned off, there may be a waiting time before disconnecting the negative (-) auxiliary battery terminal.

    Click here

  • When disconnecting and reconnecting the auxiliary battery

    HINT:

    When disconnecting and reconnecting the auxiliary battery, there is an automatic learning function that completes learning when the respective system is used.

    Click here

PROCEDURE

1.

CHECK HYBRID VEHICLE CONTROL ECU (+B1 VOLTAGE)

(a) Turn the ignition switch to ON.

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

*a

Component with harness connected

(Hybrid Vehicle Control ECU)

-

-

Standard Voltage:

Tester Connection

Condition

Specified Condition

I249-8 (+B1) - Body ground

Ignition switch ON

11 to 14 V

(c) Turn the ignition switch off.

NG

GO TO STEP 3

OK

2.

CHECK HARNESS AND CONNECTOR (HYBRID VEHICLE CONTROL ECU - BODY GROUND)

(a) Disconnect the hybrid vehicle control ECU connectors.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A192-12 (E01) - Body ground

Always

Below 1 Ω

A192-24 (E12) - Body ground

Always

Below 1 Ω

I249-1 (E1) - Body ground

Always

Below 1 Ω

(c) Reconnect the hybrid vehicle control ECU connectors.

OK

GO TO PROBLEM SYMPTOMS TABLE

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

3.

CHECK HYBRID VEHICLE CONTROL ECU (MREL TERMINAL VOLTAGE)

(a) Turn the ignition switch to ON.

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

*a

Component with harness connected

(Hybrid Vehicle Control ECU)

-

-

Standard Voltage:

Tester Connection

Condition

Specified Condition

I249-10 (MREL) - Body ground

Ignition switch ON

11 to 14 V

(c) Turn the Ignition switch off.

NG

REPLACE HYBRID VEHICLE CONTROL ECU

OK

4.

CHECK FUSE (PM-IGCT)

(a) Remove the PM-IGCT fuse from the No. 1 engine room relay block and No. 1 junction block assembly.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

PM-IGCT fuse

Always

Below 1 Ω

(c) Install the PM-IGCT fuse.

NG

GO TO STEP 11

OK

5.

CHECK FUSE (IGCT-MAIN NO. 1)

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

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

IGCT-MAIN NO. 1 fuse

Always

Below 1 Ω

(c) Install the IGCT-MAIN NO. 1 fuse.

NG

GO TO STEP 12

OK

6.

INSPECT RELAY (IGCT-MAIN NO. 1)

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

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

3 - 5

Auxiliary battery voltage not applied between terminals 1 and 2

10 kΩ or higher

Auxiliary battery voltage applied between terminals 1 and 2

Below 1 Ω

*1

IGCT-MAIN NO. 1 Relay

(c) Install the IGCT-MAIN NO. 1 relay.

NG

REPLACE RELAY (IGCT-MAIN NO. 1)
OK

7.

CHECK HARNESS AND CONNECTOR (HYBRID VEHICLE CONTROL ECU - NO. 1 ENGINE ROOM RELAY BLOCK AND NO. 1 JUNCTION BLOCK ASSEMBLY)

(a) Disconnect the hybrid vehicle control ECU connector.

(b) Remove the PM-IGCT fuse from the No. 1 engine room relay block and No. 1 junction block assembly.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

I249-8 (+B1) - 2 (PM-IGCT fuse holder)

Always

Below 1 Ω

(d) Install the PM-IGCT fuse.

(e) Reconnect the hybrid vehicle control ECU connector.

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

8.

CHECK HARNESS AND CONNECTOR (NO. 1 ENGINE ROOM RELAY BLOCK AND NO. 1 JUNCTION BLOCK ASSEMBLY)

(a) Remove the IGCT-MAIN NO. 1 fuse, PM-IGCT fuse and IGCT-MAIN NO. 1 relay from the No. 1 engine room relay block and No. 1 junction block assembly.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

5 (IGCT-MAIN NO. 1 relay holder) - 2 (IGCT-MAIN NO. 1 fuse holder)

Always

Below 1 Ω

3 (IGCT-MAIN NO. 1 relay holder) - 1 (PM-IGCT fuse holder)

Always

Below 1 Ω

(c) Install the IGCT-MAIN NO. 1 fuse, PM-IGCT fuse and IGCT-MAIN NO. 1 relay.

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

9.

CHECK HARNESS AND CONNECTOR (HYBRID VEHICLE CONTROL ECU - NO. 1 ENGINE ROOM RELAY BLOCK AND NO. 1 JUNCTION BLOCK ASSEMBLY)

(a) Disconnect the hybrid vehicle control ECU connector.

(b) Remove the IGCT-MAIN NO. 1 relay from the No. 1 engine room relay block and No. 1 junction block assembly.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

I249-10 (MREL) - 1 (IGCT-MAIN NO. 1 relay holder)

Always

Below 1 Ω

I249-10 (MREL) or 1 (IGCT-MAIN NO. 1 relay holder) - Body ground and other terminals

Always

10 kΩ or higher

(d) Install the IGCT-MAIN NO. 1 relay.

(e) Reconnect the hybrid vehicle control ECU connector.

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

10.

CHECK HARNESS AND CONNECTOR (NO. 1 ENGINE ROOM RELAY BLOCK AND NO. 1 JUNCTION BLOCK ASSEMBLY - BODY GROUND)

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

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

2 (IGCT-MAIN NO. 1 relay holder) - Body ground

Always

Below 1 Ω

(c) Install the IGCT-MAIN NO. 1 relay.

OK

CHECK FOR INTERMITTENT PROBLEMS

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

11.

CHECK HARNESS AND CONNECTOR (HYBRID VEHICLE CONTROL ECU - NO. 1 ENGINE ROOM RELAY BLOCK AND NO. 1 JUNCTION BLOCK ASSEMBLY)

(a) Remove the PM-IGCT fuse from the No. 1 engine room relay block and No. 1 junction block assembly.

(b) Disconnect the hybrid vehicle control ECU connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

I249-8 (+B1) or 2 (PM-IGCT fuse holder) - Body ground and other terminals

Always

10 kΩ or higher

(d) Reconnect the hybrid vehicle control ECU connector.

(e) Install the PM-IGCT fuse.

OK

REPLACE FUSE (IGCT SCENE)
NG

GO TO STEP 13

12.

CHECK HARNESS AND CONNECTOR (NO. 1 ENGINE ROOM RELAY BLOCK AND NO. 1 JUNCTION BLOCK ASSEMBLY)

(a) Remove the IGCT-MAIN NO. 1 fuse, PM-IGCT fuse and IGCT-MAIN NO. 1 relay from the No. 1 engine room relay block and No. 1 junction block assembly.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

5 (IGCT-MAIN NO. 1 relay holder) or 2 (IGCT-MAIN NO. 1 fuse holder) - Body ground and other terminals

Always

10 kΩ or higher

3 (IGCT-MAIN NO. 1 relay holder) or 1 (PM-IGCT fuse holder) - Body ground and other terminals

Always

10 kΩ or higher

(c) Install the IGCT-MAIN NO. 1 fuse, PM-IGCT fuse and IGCT-MAIN NO. 1 relay.

OK

REPLACE FUSE (IGCT-MAIN NO. 1)
NG

GO TO STEP 14

13.

REPAIR OR REPLACE HARNESS OR CONNECTOR
NEXT

REPLACE FUSE (IGCT-MAIN NO. 1)

14.

REPAIR OR REPLACE HARNESS OR CONNECTOR
NEXT

REPLACE FUSE (IGCT-MAIN NO. 1)

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