DTC P26CA-12: Engine Coolant Pump Circuit Short to Battery [03/2023 - ]: Procedure

WARNING: This page is about a different car, the 2025 Lexus NX 250, 2024 Lexus NX 250, 2023 Lexus NX 250, and 2022 Lexus NX 250. However, it is still accessible from the selected car via links, so may be relevant.

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

Disconnect the engine water pump assembly (water inlet housing) connector.
Turn the ignition switch to ON.

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

Standard Voltage

Tester Connection	Condition	Specified Condition
B31-2 (SWP) - Body ground	Ignition switch ON	Below 1 V

Result

Proceed to
OK
NG

Result:

See step 3

Result:

See step 2

INSPECT ECM (INTERNAL CIRCUIT)

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

Measure the resistance while maintaining at 3000 rpm.

Powertrain > Engine > Active Test

Active Test Display
Activate the Electric Water Pump

Data List Display
Electric Water Pump

Standard

Tester Connection	Condition	Specified Condition
B31-2 (SWP) - Body ground	During Active Test	Resistance fluctuates*

HINT:

*: Using the Active Test, duty control of the transistors in the ECM will be performed. Due to the duty control, resistance of the SWP terminal will be unstable during the Active Test. If the resistance fluctuates while performing the Active Test, it can be determined that the transistor is operating. If the transistor does not operate during the Active Test, the ECM may be malfunctioning.

Result

Proceed to
OK
NG

Result:

REPLACE ENGINE WATER PUMP ASSEMBLY (WATER INLET HOUSING). Refer to REMOVAL [11/2021 - ]

Result:

REPLACE ECM. Refer to REMOVAL [11/2021 - ]

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

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

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

Standard Resistance (for TMMC Made)

Tester Connection	Condition	Specified Condition
B31-2 (SWP) or B94-50 (WPO) - Other terminals	Always	10 kΩ or higher

Standard Resistance (for TMC Made)

Tester Connection	Condition	Specified Condition
B31-2 (SWP) or B50-50 (WPO) - Other terminals	Always	10 kΩ or higher

Result

Proceed to
OK
NG

Result:

REPLACE ECM. Refer to REMOVAL [11/2021 - ]

Result:

REPAIR OR REPLACE HARNESS OR CONNECTOR