Toyota Corolla Cross: Backup Boost Converter "A" (P323A00,P323A16,P323B14,P323B29,P323B38)

Toyota Corolla Cross (2022-2024) Service Manual / Engine & Hybrid System / Stop And Start / Stop And Start System / Backup Boost Converter "A" (P323A00,P323A16,P323B14,P323B29,P323B38)

DESCRIPTION

A backup boost converter is built into the engine stop and start ECU.

The backup boost converter helps maintain auxiliary battery voltage to prevent various functions from failing if power source voltage supplied from the backup boost converter drops due to the high electrical load when the engine is restarted by stop and start control.

The backup boost converter helps maintain the power source voltage if the auxiliary battery voltage drops due to the high electrical load when the engine is restarted by stop and start control.

HINT:

A relay function and fuse function are provided in the backup boost converter.

If there is a malfunction in any of the electrical system circuits connected to the backup boost converter, the fuse and relay functions shut off the malfunctioning circuit to protect other circuits (remains shut off until next trip).

When the electrical system circuit is shut off, power to the circuit is cut off, causing any systems connected to the circuit to be disabled.

The fuse function is reset* when the ignition switch is turned off. If the malfunction still exists in the electrical system circuit that has been shut off by the relay function, it will be shut off again by the relay and fuse functions the next time the ignition switch is turned to ON.

*: A semiconductor fuse self resets according to electric signal.

The backup boost converter supplies power to:

Meter / gauge system
Power steering system
Audio and visual system
Tire pressure warning system
Toyota Safety Sense
Parking support brake system

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	MIL	Warning Indicate	Note
P323A00	Backup Boost Converter "A"	The following conditions is met for 1 second or more (1 trip detection logic): Backup boost converter malfunction is detected.	Wire harness or connector Auxiliary battery BBC NO. 1 fuse BBC NO. 2 fuse Engine stop and start ECU	Comes on (For Mexico Models: Does not come on)	Does not come on (For Mexico Models: Blinks)	SAE Code: P323A
P323A16	Backup Boost Converter "A" Circuit Voltage Below Threshold	One of the following conditions is met for 2 second or more (1 trip detection logic): IG41 voltage is 6.0 V or less and backup boost converter output overcurrent is not detected. B41 or B42 voltage is 6.0 V or less, backup boost converter is not overheating and backup boost converter output overcurrent is not detected.	Wire harness or connector Auxiliary battery BBC NO. 1 fuse BBC NO. 2 fuse Engine stop and start ECU	Does not come on	Does not come on (For Mexico Models: Blinks)	SAE Code: P323A
P323B14	Backup Boost Converter "A" Control Circuit Circuit Short to Ground or Open	The following conditions is met for 1 second or more (1 trip detection logic): Backup boost converter malfunction is detected.	Wire harness or connector Auxiliary battery BBC NO. 1 fuse BBC NO. 2 fuse Engine stop and start ECU	Comes on (For Mexico Models: Does not come on)	Does not come on (For Mexico Models: Blinks)	SAE Code: P323D
P323B29	Backup Boost Converter "A" Control Circuit Signal Invalid	The following conditions is met for 1 second or more (1 trip detection logic): Backup boost converter malfunction is detected.	Wire harness or connector Auxiliary battery BBC NO. 1 fuse BBC NO. 2 fuse Engine stop and start ECU	Comes on (For Mexico Models: Does not come on)	Does not come on (For Mexico Models: Blinks)	SAE Code: P323C
P323B38	Backup Boost Converter "A" Control Circuit Signal Cycle Invalid	The following conditions is met for 1 second or more (1 trip detection logic): Backup boost converter malfunction is detected.	Wire harness or connector Auxiliary battery BBC NO. 1 fuse BBC NO. 2 fuse Engine stop and start ECU	Comes on (For Mexico Models: Does not come on)	Does not come on (For Mexico Models: Blinks)	SAE Code: P323C

MONITOR STRATEGY

Related DTCs	P323A, P323D, P323C: Starter / generator control module internal back up boost converter performance
Required Sensors/Components (Main)	Engine stop and start ECU
Required Sensors/Components (Related)	-
Frequency of Operation	Continuous
Duration	1 second
MIL Operation	Immediate
Sequence of Operation	None

TYPICAL ENABLING CONDITIONS

P323A, P323C (Case1), P323D

All of the following conditions are met	-
Battery voltage	8 V or higher
Write Inhibit	permit
Time after Write status forbiddance to permit	0.5 seconds or more
Ignition switch	ON
Time after ignition switch is off to ON	0.5 seconds or more
Starter	OFF
Time after starter on to off	0.5 seconds or more
Engine stop and start ECU internal back up boost converter fail (P323C)	Not detected

P323C (Case2)

Monitor runs whenever the following DTCs are not stored	None
All of the following conditions are met	-
Time after engine stop and start ECU power ON	0.1 seconds or more
Back up boost converter control IC status signal frequency	Less than 50 Hz

TYPICAL MALFUNCTION THRESHOLDS

P323A (Case 1)

The following condition is met	2 times or more
Back up boost converter control IC power supply voltage	Higher than 5.8 V

P323A (Case 2)

Both of the following conditions are met	20 times or more
Back up boost converter boosted voltage	17 V or higher
Time after Engine restart by engine stop and start ECU	Less than 1 second

P323A (Case 3)

Both of the following conditions are met	13 times or more
Back up boost converter boosted voltage	9 V or less
Time after Engine restart by engine stop and start ECU	Less than 1 second

P323A (Case 4)

Both of the following conditions are met	13 times or more
Back up boost converter feedback control voltage	2.7 V or higher
Time after Engine restart by engine stop and start ECU	Less than 1 second

P323A (Case 5)

Both of the following conditions are met	2 times or more
Back up boost converter boosted voltage	3 V or less
Battery voltage detected by back up boost converter control IC	4.6 V or higher

P323A (Case 6)

Both of the following conditions are met	98 times or more
Back up boost converter circuit negative power supply voltage	Higher than -1.8 V
Back up boost converter control IC power supply voltage	4.2 V or higher

P323A (Case 7)

The following condition is met	2 times or more
Difference between positive voltage and negative voltages (Back up boost converter output current sensor circuit)	Higher than 0.085 V

P323A (Case 8)

The following condition is met	8 times or more
Back up boost converter output current sensor circuit resistance	More than 450000 Ω

P323C

One of the following conditions (a), (b), (c), (d), (e), (f), (g) or (h) is met	-
(a) Number of back up boost converter control IC status signal pulse	Less than 3 times
(b) Back up boost converter control IC status signal frequency	Less than 90.91 Hz
(c) Back up boost converter control IC status signal frequency	Higher than 111.11 Hz
(d) Back up boost converter control IC status signal duty cycle	Higher than 0%, and less than 7.5%
(e) Back up boost converter control IC status signal duty cycle	Higher than 17.5%, and less than 32.5%
(f) Back up boost converter control IC status signal duty cycle	Higher than 42.5%, and less than 57.5%
(g) Back up boost converter control IC status signal duty cycle	Higher than 67.5%, and less than 82.5%
(h) Back up boost converter control IC status signal duty cycle	Higher than 92.5%, and less than 100%

P323D

Back up boost converter control IC power supply voltage

Less than 3 V

CONFIRMATION DRIVING PATTERN

HINT:

If the cable is disconnected from the auxiliary battery terminal, stop and start control is prohibited until refresh charge is completed.
In this case, let the vehicle idle to complete the refresh charge. The refresh charge is complete when the Data List item Status of Battery Charge Control changes from "Refresh Charge Mode". (Usually, by idling the engine for 5 to 60 minutes with the auxiliary battery fluid temperature at 11°C (52°F) or higher, the refresh charge will be completed.)
If the GTS is not available and the Data List item Status of Battery Charge Control cannot be checked, charge the auxiliary battery by idling the engine for approximately 5 to 60 minutes or driving the vehicle, and then drive the vehicle and check that stop and start control operates.
If the engine is started with the hood open, the system determines that a jump start has occurred. Therefore, make sure that the hood is closed before starting the engine and driving the vehicle.
After the refresh charge completes, turn the ignition switch off, wait for at least 30 seconds, and then start the engine again. If the vehicle enters refresh charge mode again while the engine is idling, the initial refresh charge did not properly complete, so wait for the refresh charge to complete.
Allow the engine to idle for 3 minutes after it is warmed up and check that the engine idle speed is within 50 rpm of the target idle speed.
When clearing the permanent DTCs, refer to the "CLEAR PERMANENT DTC" procedure (except Mexico Models).
Click here
When clearing the permanent DTCs, do not disconnect the cable from the battery terminal or attempt to clear the DTCs during this procedure, as doing so will clear the universal trip and normal judgment histories (except Mexico Models).

CONFIRMATION AFTER TROUBLESHOOTING

(a) Clear the DTCs.

Powertrain > Stop and Start > Clear DTCs

(b) Start the engine and warm it up.

CAUTION:

When performing Confirmation Driving Pattern, obey all speed limits and traffic laws.

(d) Depress the brake pedal and stop the vehicle.

(e) Keep the engine stopped by stop and start control for 1 second or more. (Keep the shift lever in D.)

(f) Release the brake pedal with the shift lever in D to start the engine.

HINT:

If the engine cranks slowly when the engine is restarted, it can be determined that the auxiliary battery voltage is low.

(g) Check that DTCs are not output.

Powertrain > Stop and Start > Trouble Codes

STOP AND START SYSTEM OPERATION CHECK

Click here

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

Before replacing the engine stop and start ECU, read the number of starter operations and write it into a new engine stop and start ECU.
Click here
After replacing the engine stop and start ECU, perform learning of the external backup boost converter (eco run vehicle converter assembly).
Click here
After replacing the engine stop and start ECU or air conditioning amplifier assembly, reset and perform learning of the air conditioning information in the engine stop and start ECU.
Click here
When the engine stop and start ECU or oil pump with motor assembly is replaced, check the oil pump with motor assembly.
Click here
Inspect the fuses for circuits related to this system before performing the following procedure.

HINT:

Using the GTS, read the freeze frame data before troubleshooting. System condition information is recorded as freeze frame data the moment a DTC is stored. This information can be useful when troubleshooting.
Click here
For wire harness and connector inspection procedures and precautions, refer to " "
DTCs for the stop and start system are not cleared even if the malfunction has been repaired. After repairing the malfunction, be sure to clear the DTCs.

PROCEDURE

1.	CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - BBC NO.1 FUSE AND BBC NO. 2 FUSE)

(a) Disconnect the A168 engine stop and start ECU connector.

(b) Remove the BBC NO. 1 fuse and BBC NO. 2 fuse from the No. 1 engine room relay block.

Standard Resistance:

Tester Connection	Condition	Specified Condition
A168-1 (BIN2) - 2 (BBC NO. 2 fuse holder)	Always	Below 1 Ω
A168-3 (BIN1) - 2 (BBC NO. 1 fuse holder)	Always	Below 1 Ω
A168-1 (BIN2) - Body ground and other terminals	Always	10 kΩ or higher
2 (BBC NO. 2 fuse holder) - Body ground and other terminals	Always	10 kΩ or higher
A168-3 (BIN1) - Body ground and other terminals	Always	10 kΩ or higher
2 (BBC NO. 1 fuse holder) - Body ground and other terminals	Always	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

2.	CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU POWER SOURCE CIRCUIT)

(a) Disconnect the A168 and I230 engine stop and start ECU connectors.

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
A168-1 (BIN2) - Body ground	Always	9.5 to 14 V
A168-3 (BIN1) - Body ground	Always	9.5 to 14 V

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
I230-18 (IGP) - Body ground	Always	9.5 to 14 V

REPAIR OR REPLACE HARNESS OR CONNECTOR

3.	CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - BODY GROUND)

(a) Disconnect the A168 and A169 engine stop and start ECU connectors.

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
A168-8 (GND1) - Body ground	Always	9.5 to 14 V
A168-2 (GND2) - Body ground	Always	9.5 to 14 V
A169-6 (DGND) - Body ground	Always	9.5 to 14 V

REPAIR OR REPLACE HARNESS OR CONNECTOR

4.	CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - EACH ECU OR SENSOR)

(a) Disconnect the I230 engine stop and start ECU connector.

(b) Disconnect the I4 combination meter assembly connector.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
I230-10 (IG12) - I4-6 (IG+)	Always	Below 1 Ω
I230-23 (IG31) - I21-1 (IG)	Always	Below 1 Ω
I230-10 (IG12) - Body ground and other terminals	Always	10 kΩ or higher
I230-23 (IG31) - Body ground and other terminals	Always	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

5.	CHECK VEHICLE SPECIFICATION

(a) Check the vehicle specification

Result	Proceed to
w/ Smart Key System	A
w/o Smart Key System	B

GO TO STEP 8

6.	CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - EACH ECU OR SENSOR)

(a) Disconnect the I230 engine stop and start ECU connector.

(b) Disconnect the O209 tire pressure warning ECU and receiver connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
I230-2 (B41) - O209-7 (+B)	Always	Below 1 Ω
I230-2 (B41) - Body ground and other terminals	Always	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

7.	CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - EACH ECU OR SENSOR)

(a) Disconnect the I230 engine stop and start ECU connector.

(b) Disconnect the I24 clearance warning ECU assembly connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
I230-3 (IG41) - I24-1 (IG)	Always	Below 1 Ω
I230-3 (IG41) - Body ground and other terminals	Always	10 kΩ or higher

REPLACE ENGINE STOP AND START ECU

REPAIR OR REPLACE HARNESS OR CONNECTOR

8.	CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - EACH ECU OR SENSOR)

(a) Disconnect the I230 engine stop and start ECU connector.

(b) Disconnect the O221 tire pressure warning ECU and receiver connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
I230-2 (B41) - O221-7 (+B)	Always	Below 1 Ω
I230-2 (B41) - Body ground and other terminals	Always	10 kΩ or higher

GO TO STEP 7

REPAIR OR REPLACE HARNESS OR CONNECTOR

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