Toyota Avalon (XX50): System Voltage Circuit Short to Ground or Open (P056014). Thermostat Heater Control Circuit Short to Battery (P059712). Thermostat Heater Control Circuit Short to Ground or Open (P059714)

Toyota Avalon (XX50) 2019-2022 Service & Repair Manual / Engine / A25a-fxs Engine Control / Sfi System / System Voltage Circuit Short to Ground or Open (P056014). Thermostat Heater Control Circuit Short to Battery (P059712). Thermostat Heater Control Circuit Short to Ground or Open (P059714)

System Voltage Circuit Short to Ground or Open (P056014)

MONITOR DESCRIPTION

The auxiliary battery supplies electricity to the ECM even when the power switch is off. This power allows the ECM to store data such as DTC history, Freeze Frame Data and fuel trim values. If the auxiliary battery voltage falls below a minimum level, the memory is cleared and the ECM determines that there is a malfunction in the power supply circuit. The ECM will illuminate the MIL and store this DTC.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	MIL	Memory	Note
P056014	System Voltage Circuit Short to Ground or Open	An open or short in the ECM backup power source circuit (1 trip detection logic).	Open or short in back up power source circuit Auxiliary battery Auxiliary battery terminals ECM	Comes on	DTC stored	SAE Code: P0562

MONITOR STRATEGY

Related DTCs	P0562: ECM system voltage range check (low voltage)
Required Sensors/Components (Main)	ECM
Required Sensors/Components (Related)	-
Frequency of Operation	Continuous
Duration	3 seconds
MIL Operation	Immediate
Sequence of Operation	None

TYPICAL ENABLING CONDITIONS

Monitor runs whenever the following DTCs are not stored	None
Both of the following conditions are met	-
Auxiliary battery voltage	8 V or higher
Power switch	On (IG)

TYPICAL MALFUNCTION THRESHOLDS

Continuous auxiliary battery voltage

Less than 3.5 V

CONFIRMATION DRIVING PATTERN

HINT:

After repair has been completed, clear the DTC and then check that the vehicle has returned to normal by performing the following All Readiness check procedure.
Click here
When clearing the permanent DTCs, refer to the "CLEAR PERMANENT DTC" procedure.
Click here

Connect the Techstream to the DLC3.
Turn the power switch on (IG).
Turn the Techstream on.
Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
Turn the power switch off and wait for at least 30 seconds.
Turn the power switch on (IG).
Turn the Techstream on.
Wait 5 seconds or more [A].
Enter the following menus: Powertrain / Engine / Trouble Codes [B].
Read the pending DTCs.
HINT:
- If a pending DTC is output, the system is malfunctioning.
- If a pending DTC is not output, perform the following procedure.
Enter the following menus: Powertrain / Engine / Utility / All Readiness.
Input the DTC: P056014.

Check the DTC judgment result.

Techstream Display	Description
NORMAL	DTC judgment completed System normal
ABNORMAL	DTC judgment completed System abnormal
INCOMPLETE	DTC judgment not completed Perform driving pattern after confirming DTC enabling conditions

HINT:

If the judgment result is NORMAL, the system is normal.
If the judgment result is ABNORMAL, the system is malfunctioning.
[A] to [B]: Normal judgment procedure.
The normal judgment procedure is used to complete DTC judgment and also used when clearing permanent DTCs.
When clearing the permanent DTCs, do not disconnect the cable from the auxiliary battery terminal or attempt to clear the DTCs during this procedure, as doing so will clear the universal trip and normal judgment histories.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

Inspect the fuses for circuits related to this system before performing the following procedure.
After turning 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
Vehicle Control History may be stored in the hybrid vehicle control ECU assembly if the engine is malfunctioning. Certain vehicle condition information is recorded when Vehicle Control History is stored. Reading the vehicle conditions recorded in both the Freeze Frame Data and Vehicle Control History can be useful for troubleshooting.
Click here

(Select Powertrain in Health Check and then check the time stamp data.)

Click here
If any "Engine Malfunction" Vehicle Control History item has been stored in the hybrid vehicle control ECU assembly, make sure to clear it. However, as all Vehicle Control History items are cleared simultaneously, if any Vehicle Control History items other than "Engine Malfunction" are stored, make sure to perform any troubleshooting for them before clearing Vehicle Control History.
Click here

HINT:

Read Freeze Frame Data using the Techstream. The ECM records vehicle and driving condition information as Freeze Frame Data the moment a DTC is stored. When troubleshooting, Freeze Frame Data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air fuel ratio was lean or rich, and other data from the time the malfunction occurred.

PROCEDURE

1.	INSPECT AUXILIARY BATTERY

(a) Inspect the auxiliary battery.

Click here

OK:

Auxiliary battery voltage is between 11 to 14 V.

CHARGE OR REPLACE AUXILIARY BATTERY

2.	CHECK AUXILIARY BATTERY TERMINAL

(a) Check that the auxiliary battery terminals are not loose or corroded.

Click here

OK:

Auxiliary battery terminals are not loose or corroded.

REPAIR OR REPLACE AUXILIARY BATTERY TERMINAL

3.	CHECK TERMINAL VOLTAGE (POWER SOURCE OF ECM)

*a	Front view of wire harness connector (to ECM)

(a) Disconnect the ECM connector.

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
A19-1 (BATT) - Body ground	Always	11 to 16 V

REPAIR OR REPLACE HARNESS OR CONNECTOR (AUXILIARY BATTERY - ECM)

CLEAR DTC

(a) Connect the Techstream to the DLC3.

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

(d) Clear the DTCs.

Powertrain > Engine > Clear DTCs

(e) Turn the power switch off and wait for at least 30 seconds.

5.	CHECK WHETHER DTC OUTPUT RECURS (DTC P056014)

(a) Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.

(b) Enter the following menus: Powertrain / Engine / Trouble Codes.

Powertrain > Engine > Trouble Codes

Result	Proceed to
DTCs are not output	A
DTC P056014 is output	B

CHECK FOR INTERMITTENT PROBLEMS

REPLACE ECM

Thermostat Heater Control Circuit Short to Battery (P059712)

DESCRIPTION

An electric heater is equipped to the temperature sensing portion of the thermostat. During normal driving, current does not flow to the heater and the thermostat functions as an ordinary thermostat. When the temperature of the engine increases by a large amount such as during high-load driving, control is performed to warm the heater of the temperature sensing portion, forcing the valve to open and causing a large amount of coolant to flow from the radiator.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	MIL	Memory	Note
P059712	Thermostat Heater Control Circuit Short to Battery	Short in thermostat heater circuit and power supply circuit (1 trip detection logic).	Short in thermostat heater circuit ECM	Comes on	DTC stored	SAE Code: P0599

Related Data List

DTC No.	Data List
P059712	Coolant Temperature

MONITOR DESCRIPTION

The ECM monitors the output voltage while the thermostat heater is operating.

The thermostat heater turns on and off according to ON/OFF switching of a transistor inside the ECM.

If a continuous mismatch occurs between the ECM transistor state and the output voltage, the ECM determines there is a malfunction in the thermostat heater circuit and stores a DTC.

MONITOR STRATEGY

Related DTCs	P0599: Thermostat heater range check (high voltage)
Required Sensors/Components (Main)	Thermostat heater
Required Sensors/Components (Related)	-
Frequency of Operation	Continuous
Duration	3 seconds
MIL Operation	Immediate
Sequence of Operation	None

TYPICAL ENABLING CONDITIONS

Monitor runs whenever the following DTCs are not stored	None
All of the following conditions are met	-
Either of the following conditions is met	1 or 2
1. Both of the following conditions are met	(a) and (b)
(a) Last thermostat heater output terminal voltage level	Low
(b) Current thermostat heater output terminal voltage level	Low
2. Both of the following conditions are met	(c) and (d)
(c) Last thermostat heater output terminal voltage level	High
(d) Current thermostat heater output terminal voltage level	High
Auxiliary battery voltage	8 V or higher
Command to thermostat heater	On

TYPICAL MALFUNCTION THRESHOLDS

Thermostat heater output terminal voltage level

High

CONFIRMATION DRIVING PATTERN

HINT:

After repair has been completed, clear the DTC and then check that the vehicle has returned to normal by performing the following All Readiness check procedure.
Click here
When clearing the permanent DTCs, refer to the "CLEAR PERMANENT DTC" procedure.
Click here

Connect the Techstream to the DLC3.
Turn the power switch on (IG).
Turn the Techstream on.
Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
Turn the power switch off and wait for at least 30 seconds.
Turn the power switch on (IG).
Turn the Techstream on.
Put the engine in Inspection Mode (Maintenance Mode).
Click here
Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher [A].
Enter the following menus: Powertrain / Engine / Data List / Calculate Load and Coolant Temperature.
With the engine running, drive the vehicle for at least 3 seconds at the Calculate Load of 45% or more and the Coolant Temperature of 90°C (194°F) or higher [B].
CAUTION:

When performing the confirmation driving pattern, obey all speed limits and traffic laws.

HINT:

If the engine stops, further depress the accelerator pedal to restart the engine.
Stop the vehicle.
Enter the following menus: Powertrain / Engine / Trouble Codes [C].
Read the pending DTCs.
HINT:
- If a pending DTC is output, the system is malfunctioning.
- If a pending DTC is not output, perform the following procedure.
Enter the following menus: Powertrain / Engine / Utility / All Readiness.
Input the DTC: P059712.

Check the DTC judgment result.

Techstream Display	Description
NORMAL	DTC judgment completed System normal
ABNORMAL	DTC judgment completed System abnormal
INCOMPLETE	DTC judgment not completed Perform driving pattern after confirming DTC enabling conditions

HINT:

If the judgment result is NORMAL, the system is normal.
If the judgment result is ABNORMAL, the system has a malfunction.
If the judgment result is INCOMPLETE, perform the steps [B] through [C] again.
[A] to [C]: Normal judgment procedure.
The normal judgment procedure is used to complete DTC judgment and also used when clearing permanent DTCs.
When clearing the permanent DTCs, do not disconnect the cable from the auxiliary battery terminal or attempt to clear the DTCs during this procedure, as doing so will clear the universal trip and normal judgment histories.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

Inspect the fuses for circuits related to this system before performing the following procedure.
Vehicle Control History may be stored in the hybrid vehicle control ECU assembly if the engine is malfunctioning. Certain vehicle condition information is recorded when Vehicle Control History is stored. Reading the vehicle conditions recorded in both the Freeze Frame Data and Vehicle Control History can be useful for troubleshooting.
Click here

(Select Powertrain in Health Check and then check the time stamp data.)

Click here
If any "Engine Malfunction" Vehicle Control History item has been stored in the hybrid vehicle control ECU assembly, make sure to clear it. However, as all Vehicle Control History items are cleared simultaneously, if any Vehicle Control History items other than "Engine Malfunction" are stored, make sure to perform any troubleshooting for them before clearing Vehicle Control History.
Click here

HINT:

PROCEDURE

1.	CHECK HARNESS AND CONNECTOR (THERMOSTAT HEATER (WATER INLET WITH THERMOSTAT SUB-ASSEMBLY) - ECM)

(a) Disconnect the thermostat heater (water inlet with thermostat sub-assembly) connector.

(b) Disconnect the ECM connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
U4-2 or C55-7 (HTHM) - other terminals	Always	10 kΩ or higher

REPLACE ECM

REPAIR OR REPLACE HARNESS OR CONNECTOR

Thermostat Heater Control Circuit Short to Ground or Open (P059714)

DESCRIPTION

Refer to DTC P059712.

Click here

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	MIL	Memory	Note
P059714	Thermostat Heater Control Circuit Short to Ground or Open	Open or short in thermostat heater circuit and power supply circuit (1 trip detection logic).	Open or short in thermostat heater circuit Thermostat heater (water inlet with thermostat sub-assembly) ECM	Comes on	DTC stored	SAE Code: P0598

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

MIL

Memory

Note

P059714

Thermostat Heater Control Circuit Short to Ground or Open

Open or short in thermostat heater circuit and power supply circuit

(1 trip detection logic).

Open or short in thermostat heater circuit
Thermostat heater (water inlet with thermostat sub-assembly)
ECM

Comes on

DTC stored

SAE Code: P0598

Related Data List

DTC No.	Data List
P059714	Coolant Temperature

MONITOR DESCRIPTION

The ECM monitors the output voltage while the thermostat heater is operating.

The thermostat heater turns on and off according to ON/OFF switching of a transistor inside the ECM.

If a continuous mismatch occurs between the ECM transistor state and the output voltage, the ECM determines there is a malfunction in the thermostat heater circuit and stores a DTC.

MONITOR STRATEGY

Related DTCs	P0598: Thermostat heater range check (low voltage)
Required Sensors/Components (Main)	Thermostat heater
Required Sensors/Components (Related)	-
Frequency of Operation	Continuous
Duration	3 seconds
MIL Operation	Immediate
Sequence of Operation	None

TYPICAL ENABLING CONDITIONS

Monitor runs whenever the following DTCs are not stored	None
All of the following conditions are met	-
Either of the following conditions is met	1 or 2
1. Both of the following conditions are met	(a) and (b)
(a) Last thermostat heater output terminal voltage level	Low
(b) Current thermostat heater output terminal voltage level	Low
2. Both of the following conditions are met	(c) and (d)
(c) Last thermostat heater output terminal voltage level	High
(d) Current thermostat heater output terminal voltage level	High
Auxiliary battery voltage	8 V or higher
Command to thermostat heater	Off

TYPICAL MALFUNCTION THRESHOLDS

Thermostat heater output terminal voltage level

Low

CONFIRMATION DRIVING PATTERN

HINT:

After repair has been completed, clear the DTC and then check that the vehicle has returned to normal by performing the following All Readiness check procedure.
Click here
When clearing the permanent DTCs, refer to the "CLEAR PERMANENT DTC" procedure.
Click here

Connect the Techstream to the DLC3.
Turn the power switch on (IG).
Turn the Techstream on.
Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
Turn the power switch off and wait for at least 30 seconds.
Turn the power switch on (IG).
Turn the Techstream on.
Put the engine in Inspection Mode (Maintenance Mode).
Click here
Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher [A].
Enter the following menus: Powertrain / Engine / Data List / Calculate Load and Coolant Temperature.
With the engine running, drive the vehicle for at least 3 seconds at the Calculate Load of 45% or more and the Coolant Temperature of 90°C (194°F) or higher [B].
CAUTION:

When performing the confirmation driving pattern, obey all speed limits and traffic laws.

HINT:

If the engine stops, further depress the accelerator pedal to restart the engine.
Stop the vehicle.
Enter the following menus: Powertrain / Engine / Trouble Codes [C].
Read the pending DTCs.
HINT:
- If a pending DTC is output, the system is malfunctioning.
- If a pending DTC is not output, perform the following procedure.
Enter the following menus: Powertrain / Engine / Utility / All Readiness.
Input the DTC: P059714.

Check the DTC judgment result.

Techstream Display	Description
NORMAL	DTC judgment completed System normal
ABNORMAL	DTC judgment completed System abnormal
INCOMPLETE	DTC judgment not completed Perform driving pattern after confirming DTC enabling conditions

HINT:

If the judgment result is NORMAL, the system is normal.
If the judgment result is ABNORMAL, the system has a malfunction.
If the judgment result is INCOMPLETE, perform the steps [B] through [C] again.
[A] to [C]: Normal judgment procedure.
The normal judgment procedure is used to complete DTC judgment and also used when clearing permanent DTCs.
When clearing the permanent DTCs, do not disconnect the cable from the auxiliary battery terminal or attempt to clear the DTCs during this procedure, as doing so will clear the universal trip and normal judgment histories.

WIRING DIAGRAM

Refer to DTC P059712.

Click here

CAUTION / NOTICE / HINT

NOTICE:

Inspect the fuses for circuits related to this system before performing the following procedure.
Vehicle Control History may be stored in the hybrid vehicle control ECU assembly if the engine is malfunctioning. Certain vehicle condition information is recorded when Vehicle Control History is stored. Reading the vehicle conditions recorded in both the Freeze Frame Data and Vehicle Control History can be useful for troubleshooting.
Click here

(Select Powertrain in Health Check and then check the time stamp data.)

Click here
If any "Engine Malfunction" Vehicle Control History item has been stored in the hybrid vehicle control ECU assembly, make sure to clear it. However, as all Vehicle Control History items are cleared simultaneously, if any Vehicle Control History items other than "Engine Malfunction" are stored, make sure to perform any troubleshooting for them before clearing Vehicle Control History.
Click here

HINT:

PROCEDURE

1.	CHECK TERMINAL VOLTAGE (POWER SOURCE OF THERMOSTAT HEATER (WATER INLET WITH THERMOSTAT SUB-ASSEMBLY))

*a	Front view of wire harness connector (to Thermostat Heater (Water Inlet with Thermostat Sub-assembly))

(a) Disconnect the thermostat heater (water inlet with thermostat sub-assembly) connector.

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
U4-1 - Body ground	Power switch on (IG)	11 to 14 V

GO TO STEP 4

2.	INSPECT THERMOSTAT HEATER (WATER INLET WITH THERMOSTAT SUB-ASSEMBLY)

(a) Inspect the thermostat heater (water inlet with thermostat sub-assembly).

Click here

REPLACE THERMOSTAT HEATER (WATER INLET WITH THERMOSTAT SUB-ASSEMBLY)

3.	CHECK HARNESS AND CONNECTOR (THERMOSTAT HEATER (WATER INLET WITH THERMOSTAT SUB-ASSEMBLY) - ECM)

(a) Disconnect the thermostat heater (water inlet with thermostat sub-assembly) connector.

(b) Disconnect the ECM connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
U4-2 - C55-7 (HTHM)	Always	Below 1 Ω
U4-2 or C55-7 (HTHM) - Body ground and other terminals	Always	10 kΩ or higher

REPLACE ECM

REPAIR OR REPLACE HARNESS OR CONNECTOR

4.	INSPECT EFI-MAIN NO. 2 RELAY

(a) Inspect the EFI-MAIN NO. 2 relay.

Click here

REPLACE EFI-MAIN NO. 2 RELAY

5.	CHECK TERMINAL VOLTAGE (POWER SOURCE OF EFI-MAIN NO. 2 RELAY)

*1	No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly
*2	EFI-MAIN NO. 2 Relay

(a) Remove the EFI-MAIN NO. 2 relay from the No. 1 engine room relay block and No. 1 junction block assembly.

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
3 (EFI-MAIN NO. 2 relay) - Body ground	Always	11 to 14 V

REPAIR OR REPLACE HARNESS OR CONNECTOR (AUXILIARY BATTERY - EFI-MAIN NO. 2 RELAY)

6.	CHECK HARNESS AND CONNECTOR (EFI-MAIN NO. 2 RELAY - BODY GROUND)

(a) Remove the EFI-MAIN NO. 2 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
1 (EFI-MAIN NO. 2 relay) - Body ground	Always	Below 1 Ω

REPAIR OR REPLACE HARNESS OR CONNECTOR

7.	CHECK HARNESS AND CONNECTOR (EFI-MAIN NO. 2 RELAY - THERMOSTAT HEATER (WATER INLET WITH THERMOSTAT SUB-ASSEMBLY))

(a) Remove the EFI-MAIN NO. 2 relay from the No. 1 engine room relay block and No. 1 junction block assembly.

(b) Disconnect the thermostat heater (water inlet with thermostat sub-assembly) connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
5 (EFI-MAIN NO. 2 relay) - U4-1	Always	Below 1 Ω
5 (EFI-MAIN NO. 2 relay) or U4-1 - Body ground and other terminals	Always	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR (EFI-MAIN NO. 1 RELAY - EFI-MAIN NO. 2 RELAY)

REPAIR OR REPLACE HARNESS OR CONNECTOR

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See More:

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