Lexus ES: Engine Coolant Pump Actuator Stuck (P26CB71)

Lexus ES (XZ10) Service Manual / Engine & Hybrid System / A25a-fxs (engine Control) / Sfi System / Engine Coolant Pump Actuator Stuck (P26CB71)

DESCRIPTION

Refer to DTC P26CA12.

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DTC No.	Detection Item	DTC Detection Condition	Trouble Area	MIL	Memory	Note
P26CB71	Engine Coolant Pump Actuator Stuck	Even though an operation request signal is being output, the water inlet housing with water pump sub-assembly does not rotate* (1 trip detection logic).	Lack of engine coolant Engine coolant leak Water inlet housing with water pump sub-assembly ECM	Comes on	DTC stored	SAE Code: P26CB

*: As the frequency signal (WPI) is 4 Hz when the water inlet housing with water pump sub-assembly is stopped to enable the ECM to detect an open or short in the signal line, the water inlet housing with water pump sub-assembly speed will be displayed as approximately 160 rpm even when the pump is stopped. If there is an open in the WPI circuit, the water inlet housing with water pump sub-assembly speed will be displayed as 0 rpm.

Related Data List

DTC No.	Data List
P26CB71	Coolant Temperature Electric Water Pump Target Speed Electric Water Pump Speed

MONITOR DESCRIPTION

The ECM receives a frequency signal (WPI) from the water inlet housing with water pump sub-assembly and calculates the speed of the water inlet housing with water pump sub-assembly. The ECM outputs an operation duty signal (WPO) to steplessly control the speed of the water inlet housing with water pump sub-assembly. If the duty signal (WPI) indicates that the water inlet housing with water pump sub-assembly is stopped even though the ECM is outputting an operation duty signal (WPO), the ECM judges that the water inlet housing with water pump sub-assembly is stuck and stores this DTC.

As the frequency signal (WPI) is 4 Hz when the water inlet housing with water pump sub-assembly is stopped to enable the ECM to detect an open or short in the signal line, the water inlet housing with water pump sub-assembly speed will be displayed as approximately 160 rpm even when the pump is stopped.

MONITOR STRATEGY

Related DTCs	P26CB: Engine water pump motor lock
Required Sensors/Components (Main)	Water inlet housing with water pump sub-assembly
Required Sensors/Components (Related)	-
Frequency of Operation	Continuous
Duration	Less than 65 seconds
MIL Operation	Immediate
Sequence of Operation	None

TYPICAL ENABLING CONDITIONS

All of the following conditions are met	-
Engine coolant temperature	-10°C (-50°F) or higher
Engine water pump output duty ratio	30 to 85%
Auxiliary battery voltage	Higher than 8 V
Engine coolant temperature sensor malfunction (P0117, P0118)	Not detected
Engine water pump (IN) malfunction (P26CA)	Not detected
Engine water pump (OUT) malfunction (P26CC, P26CD)	Not detected

TYPICAL MALFUNCTION THRESHOLDS

All of the following conditions are met	15 seconds or more
(a) Out of step reset operation*	Activated
(b) Engine water pump (IN) motor speed	100 rpm or higher
(c) Engine water pump (IN) motor speed	Less than 170 rpm
*: Out step reset operation when following conditions are met	-
Engine water pump command duty ratio	30 to 85%
Engine water pump (IN) motor speed	Less than 170 rpm

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.
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When clearing the permanent DTCs, refer to the "CLEAR PERMANENT DTC" procedure.
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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) [A].
Turn the Techstream on.
Put the engine in Inspection Mode (Maintenance Mode).
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Start the engine and maintain the engine speed at 2500 rpm or more for at least 75 seconds [B].
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: P26CB71.

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 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 P26CA12.

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CAUTION / NOTICE / HINT

NOTICE:

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

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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.
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HINT:

As the frequency signal (WPI) is 4 Hz when the water inlet housing with water pump sub-assembly is stopped to enable the ECM to detect an open or short in the signal line, the water inlet housing with water pump sub-assembly speed will be displayed as approximately 160 rpm even when the pump is stopped.
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.	CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P26CB71)

(a) Connect the Techstream to the DLC3.

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

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

(e) Read the DTCs.

Powertrain > Engine > Trouble Codes

Result	Proceed to
DTC P26CB71 is output	A
DTC P26CB71 and P26CE37 are output	A
DTC P26CB71 and other DTCs are output	B

HINT:

If any DTCs other than P26CB71 are output, troubleshoot those DTCs first.

GO TO DTC CHART

2.	CHECK ENGINE COOLANT LEVEL IN RESERVOIR TANK

(a) Check that the engine coolant level is between the FULL and LOW lines.

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Result	Proceed to
Engine coolant level is above the LOW line	A
Engine coolant level is below the LOW line	B

GO TO STEP 6

3.	CHECK FOR ENGINE COOLANT LEAKS

(a) Check the areas around the engine and heater for engine coolant leaks.

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HINT:

If the engine oil is cloudy during the engine oil level gauge check, it means that engine coolant has entered the engine lubrication system.

OK:

No leaks.

GO TO STEP 5

4.	ADD ENGINE COOLANT

(a) Fill the reservoir tank up to the FULL line with engine coolant.

NOTICE:

Make sure not to add engine coolant when the engine is hot.

GO TO STEP 6

5.	REPAIR OR REPLACE MALFUNCTIONING PARTS, COMPONENT AND AREA

(a) Repair any engine coolant leaks.

HINT:

Add engine coolant and perform air bleeding after repair.

6.	PERFORM ACTIVE TEST USING TECHSTREAM (ACTIVATE THE ELECTRIC WATER PUMP)

(a) Connect the Techstream to the DLC3.

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

(d) Enter the following menus: Powertrain / Engine / Active Test / Activate the Electric Water Pump / Data List / Electric Water Pump Speed.

Powertrain > Engine > Active Test

Active Test Display
Activate the Electric Water Pump

Data List Display
Electric Water Pump Speed

(e) According to the display on the Techstream, read the Data List while performing the Active Test.

Standard:

Active Test Operation	Electric Water Pump Speed
3000 rpm	2000 rpm or higher

GO TO STEP 8

7.	INSPECT ECM (INTERNAL CIRCUIT)

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

(a) Disconnect the water inlet housing with water pump sub-assembly connector.

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

Standard:

Tester Connection	Condition	Specified Condition
C66-2 (SWP) - Body ground	Power switch on (IG)	Resistance fluctuates*

HINT:

*: When the connector of the water inlet housing with water pump sub-assembly is disconnected, the ECM will enter fail-safe mode. When the ECM is in fail-safe mode, a continuous duty signal will be output and the resistance will fluctuate as the transistor inside the ECM is turned on an off.
If the resistance fluctuates while the ECM is in fail-safe mode after the connector of the water inlet housing with water pump sub-assembly is disconnected, it can be determined that the transistor is operating.
If the transistor is not operating, the ECM may be malfunctioning.
If the resistance fluctuates after turning the power switch on (IG), it can be determined that the ECM is in fail-safe mode.

REPLACE ECM

8.	REPLACE WATER INLET HOUSING WITH WATER PUMP SUB-ASSEMBLY

(a) Replace the water inlet housing with water pump sub-assembly.

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HINT:

When replacing any cooling system parts, if excessive deposits of rust or scale exist or the concentration of the engine coolant is abnormal, replace the engine coolant.

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.

10.	CHECK WHETHER DTC OUTPUT RECURS (DTC P26CB71)

(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

HINT:

If no DTC is output, the repair has been successfully completed.

END

SEE MORE:

High Voltage Power Resource Circuit Short during Pre-Charge (P300449)

DTC SUMMARY MALFUNCTION DESCRIPTION The hybrid vehicle control ECU monitors the high-voltage wiring between the HV battery and inverter with converter assembly and detects an open circuit malfunction. The cause of this malfunction may be one of the following: Inverter voltage sensor (VH) internal c

Dtc Check / Clear

DTC CHECK / CLEAR CHECK DTC (a) Connect the Techstream to the DLC3. (b) Turn the engine switch on (IG). (c) Turn the Techstream on. (d) Enter the following menus: Body Electrical / (desired system) / Trouble Codes. Body Electrical > Master Switch > Trouble Codes Body Electrical > D-Door Mot

Lexus ES: Engine Coolant Pump Actuator Stuck (P26CB71)

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SEE MORE:

High Voltage Power Resource Circuit Short during Pre-Charge (P300449)

Dtc Check / Clear