HYBRID / BATTERY CONTROL: HYBRID CONTROL SYSTEM (for NICKEL METAL HYDRIDE BATTERY): ECU Power Source Circuit; 2020 - 2022 MY Corolla Corolla HV [01/2019

Last Modified: 07-31-2024	6.11:8.1.0	Doc ID: RM100000001GCMO
Model Year Start: 2020	Model: Corolla	Prod Date Range: [01/2019 - 09/2022]
Title: HYBRID / BATTERY CONTROL: HYBRID CONTROL SYSTEM (for NICKEL METAL HYDRIDE BATTERY): ECU Power Source Circuit; 2020 - 2022 MY Corolla Corolla HV [01/2019 - 09/2022]

ECU Power Source Circuit

DESCRIPTION

If the power switch is on (IG), the hybrid vehicle control ECU applies current to the MREL terminal to turn the IGCT relay on. This supplies power to the +B1 and +B2 terminals.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

After turning the power switch off, waiting time may be required before disconnecting the cable from the negative (-) auxiliary battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) auxiliary battery terminal notices before proceeding with work.

Click here

PROCEDURE

1.	CHECK HYBRID VEHICLE CONTROL ECU (+B1, +B2 VOLTAGE)

(a) Turn the power switch on (IG).

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

Component with harness connected

(Hybrid Vehicle Control ECU)

Standard Voltage:

Tester Connection	Condition	Specified Condition
A57-11 (+B1) - Body ground	Power switch on (IG)	11 to 14 V
I3-1 (+B2) - Body ground	Power switch on (IG)	11 to 14 V

GO TO STEP 3

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

(a) Disconnect the I2 and I3 hybrid vehicle control ECU connectors.

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

Front view of wire harness connector

(to Hybrid Vehicle Control ECU)

Standard Resistance:

Tester Connection	Condition	Specified Condition
I3-3 (E1) - Body ground	Always	Below 1 Ω
I2-12 (E01) - Body ground	Always	Below 1 Ω
I2-11 (E02) - Body ground	Always	Below 1 Ω
I2-34 (E12) - Body ground	Always	Below 1 Ω

GO TO PROBLEM SYMPTOMS TABLE

REPAIR OR REPLACE HARNESS OR CONNECTOR

3.	CHECK HYBRID VEHICLE CONTROL ECU (MREL VOLTAGE)

(a) Turn the power switch on (IG).

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

Component with harness connected

(Hybrid Vehicle Control ECU)

Standard Voltage:

Tester Connection	Condition	Specified Condition
A57-5 (MREL) - Body ground	Power switch on (IG)	11 to 14 V

REPLACE HYBRID VEHICLE CONTROL ECU

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.

*1	No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly
*2	PM-IGCT Fuse

(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

GO TO STEP 11

5.	CHECK FUSE (IGCT-IG)

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

*1	No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly
*2	IGCT-IG Fuse

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
IGCT-IG fuse	Always	Below 1 Ω

GO TO STEP 12

6.	INSPECT RELAY (IGCT)

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

*1	No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly
*2	IGCT Relay

(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
3 - 5	Auxiliary battery voltage applied between terminals 1 and 2	Below 1 Ω

*1	IGCT Relay

REPLACE RELAY (IGCT)

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

(a) Disconnect the A57 and I3 hybrid vehicle control ECU connectors.

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

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

PM-IGCT Fuse Holder

Front view of wire harness connector

(to Hybrid Vehicle Control ECU)

Standard Resistance:

Tester Connection	Condition	Specified Condition
A57-11 (+B1) - 2 (PM-IGCT fuse holder)	Always	Below 1 Ω
I3-1 (+B2) - 2 (PM-IGCT fuse holder)	Always	Below 1 Ω

(d) Install the PM-IGCT fuse.

(e) Reconnect the A57 and I3 hybrid vehicle control ECU connectors.

REPAIR OR REPLACE HARNESS OR CONNECTOR

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

(a) Remove the IGCT-IG fuse, PM-IGCT fuse and IGCT 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 (IGCT relay holder) - 2 (IGCT-IG fuse holder)	Always	Below 1 Ω
5 (IGCT relay holder) - 1 (PM-IGCT fuse holder)	Always	Below 1 Ω

*1	No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly
*2	PM-IGCT Fuse Holder
*3	IGCT-IG Fuse Holder
*4	IGCT Relay Holder

REPAIR OR REPLACE HARNESS OR CONNECTOR

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

(a) Disconnect the A57 hybrid vehicle control ECU connector.

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

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

IGCT Relay Holder

Front view of wire harness connector

(to Hybrid Vehicle Control ECU)

Standard Resistance:

Tester Connection	Condition	Specified Condition
A57-5 (MREL) - 1 (IGCT relay holder)	Always	Below 1 Ω
A57-5 (MREL) or 1 (IGCT relay holder) - Body ground and other terminals	Always	10 kΩ or higher

(d) Install the IGCT relay.

(e) Reconnect the A57 hybrid vehicle control ECU connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR

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

(a) Remove the IGCT 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 relay holder) - Body ground	Always	Below 1 Ω

*1	No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly
*2	IGCT Relay Holder

CHECK FOR INTERMITTENT PROBLEMS

REPAIR OR REPLACE HARNESS OR CONNECTOR

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

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

(b) Disconnect the A57 and I3 hybrid vehicle control ECU connectors.

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

PM-IGCT Fuse Holder

Front view of wire harness connector

(to Hybrid Vehicle Control ECU)

Standard Resistance:

Tester Connection	Condition	Specified Condition
A57-11 (+B1) or 2 (PM-IGCT fuse holder) - Body ground and other terminals	Always	10 kΩ or higher
I3-1 (+B2) or 2 (PM-IGCT fuse holder) - Body ground and other terminals	Always	10 kΩ or higher

(d) Reconnect the A57 and I3 hybrid vehicle control ECU connectors.

(e) Install the PM-IGCT fuse.

REPLACE FUSE (PM-IGCT)

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-IG fuse, PM-IGCT fuse and IGCT 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 (IGCT relay holder) or 2 (IGCT-IG fuse holder) - Body ground and other terminals	Always	10 kΩ or higher
5 (IGCT relay holder) or 1 (PM-IGCT fuse holder) - Body ground and other terminals	Always	10 kΩ or higher

*1	No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly
*2	PM-IGCT Fuse Holder
*3	IGCT-IG Fuse Holder
*4	IGCT Relay Holder

REPLACE RELAY (IGCT-IG)

GO TO STEP 14

13.	REPAIR OR REPLACE HARNESS OR CONNECTOR

REPLACE FUSE (PM-IGCT)

14.	REPAIR OR REPLACE HARNESS OR CONNECTOR

REPLACE FUSE (IGCT-IG)