Last Modified: 05-13-2024 6.11:8.1.0 Doc ID: RM1000000028LT2
Model Year Start: 2023 Model: Corolla Hatchback Prod Date Range: [11/2022 - 03/2023]
Title: M20A-FKS (ENGINE CONTROL): SFI SYSTEM: P26CA12; Engine Coolant Pump Circuit Short to Battery; 2023 MY Corolla Corolla Hatchback [11/2022 - 03/2023]

DTC

P26CA12

Engine Coolant Pump Circuit Short to Battery

DESCRIPTION

The ECM calculates the necessary cooling amount based on the engine coolant temperature, engine speed and vehicle speed, and controls the engine water pump assembly accordingly. The engine water pump assembly controls the speed of the engine water pump assembly steplessly and optimally based on a duty cycle signal sent by the ECM, which reduces engine warm-up time, improves fuel efficiency and reduces cooling loss.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

MIL

Memory

Note

P26CA12

Engine Coolant Pump Circuit Short to Battery

The operation duty ratio signal (WPO) of the engine water pump assembly is a certain value or more when the engine water pump assembly operation signal is being output (1 trip detection logic).

  • Short in engine water pump assembly (water inlet housing) circuit
  • Engine water pump assembly (water inlet housing)
  • ECM

Comes on

DTC stored

  • SAE Code: P26CD
  • DTC for Mexico Models: Applies

Related Data List

DTC No.

Data List

P26CA12

  • Coolant Temperature
  • Electric Water Pump Target Speed
  • Electric Water Pump Speed

MONITOR DESCRIPTION

The ECM outputs an operation duty signal (WPO) to steplessly control the speed of the engine water pump assembly. The ECM outputs an operation duty signal (WPO) to the engine water pump assembly and monitors the actual duty signal (WPO) being output. When the actual operation duty signal (WPO) exceeds a certain value when outputting an operation duty signal (WPO) to the engine water pump assembly, the ECM detects a malfunction and stores a DTC.

MONITOR STRATEGY

Related DTCs

P26CD: Engine water pump circuit range check (High voltage)

Required Sensors/Components (Main)

Engine water pump assembly

Required Sensors/Components (Related)

-

Frequency of Operation

Continuous

Duration

3 seconds

MIL Operation

Immediate

Sequence of Operation

None

TYPICAL ENABLING CONDITIONS

All of the following conditions are met

-

Battery voltage

8 V or higher

Ignition switch

ON

Time after ignition switch off to ON

0.5 seconds or more

Output duty cycle

30 to 85%

Starter

Off

Engine water pump circuit pulse input fail (P26CA)

Not detected

TYPICAL MALFUNCTION THRESHOLDS

Both of the following conditions are met

-

Engine water pump assembly output terminal voltage level

High

Engine water pump assembly output signal

No signal

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 2023 - 2025 MY Corolla Corolla Hatchback [11/2022 -        ]; M20A-FKS (ENGINE CONTROL): SFI SYSTEM: DTC CHECK / CLEAR

  • When clearing the permanent DTCs, refer to the "CLEAR PERMANENT DTC" procedure.

    Click here 2023 - 2025 MY Corolla Corolla Hatchback [11/2022 -        ]; M20A-FKS (ENGINE CONTROL): SFI SYSTEM: DTC CHECK / CLEAR

  1. Connect the Techstream to the DLC3.
  2. Turn the ignition switch to ON.
  3. Turn the Techstream on.
  4. Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
  5. Turn the ignition switch off and wait for at least 30 seconds.
  6. Turn the ignition switch to ON [A].
  7. Turn the Techstream on.
  8. Move the shift lever to P [B].
  9. Start the engine and maintain the engine speed at 2500 rpm or more for at least 40 seconds [C].
  10. Enter the following menus: Powertrain / Engine / Trouble Codes [D].
  11. 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.
  12. Enter the following menus: Powertrain / Engine / Utility / All Readiness.
  13. Input the DTC: P26CA12.
  14. 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 [D] again.
    • [A] to [D]: 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 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

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.

CHECK TERMINAL VOLTAGE (POWER SOURCE OF ENGINE WATER PUMP ASSEMBLY (WATER INLET HOUSING))

*a

Front view of wire harness connector

(to Engine Water Pump Assembly(Water Inlet Housing))

(a) Disconnect the engine water pump assembly (water inlet housing) connector.

(b) Turn the ignition switch to ON.

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

C126-3 (SWP) - Body ground

Ignition switch ON

Below 1 V

NG

GO TO STEP 3

OK

2.

INSPECT ECM (INTERNAL CIRCUIT)

*a

Front view of wire harness connector

(to Engine Water Pump Assembly(Water Inlet Housing))

(a) Disconnect the engine water pump assembly (water inlet housing) connector.

(b) Turn the ignition switch to ON.

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

Standard:

Tester Connection

Condition

Specified Condition

C126-3 (SWP) - Body ground

Ignition switch ON

Resistance fluctuates*

HINT:

  • *: When the connector of the engine water pump assembly is disconnected, the ECM will enter fail-safe mode. In this case, duty control of the transistors in the ECM will be performed and resistance fluctuates.
  • If the resistance fluctuates while the ECM is in fail-safe mode after the connector of the engine water pump assembly is disconnected, it can be determined that the transistor is operating.
  • If the transistor does not operate, the ECM may be malfunctioning.
  • If the resistance fluctuates after turning the ignition switch to ON, it can be determined that the ECM is in fail-safe mode.
OK

REPLACE ENGINE WATER PUMP ASSEMBLY (WATER INLET HOUSING)

NG

REPLACE ECM

3.

CHECK HARNESS AND CONNECTOR (ENGINE WATER PUMP ASSEMBLY (WATER INLET HOUSING) - ECM)

(a) Disconnect the engine water pump assembly (water inlet housing) connector.

(b) Disconnect the ECM connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

C126-3 (SWP) or C76-50 (WPO) - Other terminals

Always

10 kΩ or higher

OK

REPLACE ECM

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR