Lexus RX (RX 350L, RX450h) 2016-2022 Repair Manual: Cooling Fan Circuit

DESCRIPTION

The ECM calculates an appropriate cooling fan speed based on the engine coolant temperature, air conditioning switch condition, refrigerant pressure, engine speed and vehicle speed. The cooling fan ECUs control each cooling fan speed based on the duty cycle calculated by the ECM. By optimally controlling the cooling fan speed via the cooling fan ECUs based on the conditions of the vehicle, the ECM can achieve both high cooling performance and quietness.

WIRING DIAGRAM

Refer to the System Diagram.

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CAUTION / NOTICE / HINT

NOTICE:

  • Inspect the fuses for circuits related to this system before performing the following procedure.
  • Before replacing the ECM, refer to Registration.

    Click here

PROCEDURE

1.

PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE ENGINE COOLING FAN DUTY RATIO)

(a) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine / Active Test / Control the Engine Cooling Fan Duty Ratio.

Powertrain > Engine > Active Test

Tester Display

Control the Engine Cooling Fan Duty Ratio

(e) Perform the Active Test according to the display on the Techstream.

OK:

Active Test Operation

Fan Operation

30 - 100%

Cooling fans operate

0%

Cooling fans stop

Result

Proceed to

OK

A

NG (Cooling fans do not operate)

B

NG (Cooling fans do not stop)

C

A

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

C

GO TO STEP 10

B

2.

CHECK COOLING FAN SYSTEM

(a) Disconnect the D2 ECM connector.

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

(c) Check the operation of the cooling fans.

OK:

Cooling fans operate.

OK

REPLACE ECM

NG

3.

INSPECT COOLING FAN MOTOR (COOLING FAN MOTOR LH AND COOLING FAN MOTOR RH)

(a) Inspect the cooling fan motor LH and cooling fan motor RH.

Click here

Result

Proceed to

OK

A

NG (Cooling fan motor LH)

B

NG (Cooling fan motor RH)

C

B

REPLACE COOLING FAN MOTOR LH

C

REPLACE COOLING FAN MOTOR RH

A

4.

CHECK HARNESS AND CONNECTOR (COOLING FAN ECU POWER SOURCE CIRCUIT)

(a) Disconnect the A4 cooling fan ECU connector.

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

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

A4-3 (+B1) - A4-1 (E1)

Engine switch on (IG)

11 to 14 V

*a

Front view of wire harness connector

(to Cooling Fan ECU)

NG

GO TO STEP 6

OK

5.

CHECK HARNESS AND CONNECTOR (ECM - COOLING FAN ECU)

(a) Disconnect the D2 ECM connector.

(b) Disconnect the A4 cooling fan ECU connector.

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

Standard Resistance (Check for Short):

Tester Connection

Condition

Specified Condition

D2-136 (RFC) or A4-2 (SI) - Body ground

Always

10 kΩ or higher

OK

REPLACE COOLING FAN ECU

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (ECM - COOLING FAN ECU)

6.

CHECK HARNESS AND CONNECTOR (COOLING FAN ECU - BODY GROUND)

(a) Disconnect the A4 cooling fan ECU connector.

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

Standard Resistance (Check for Open):

Tester Connection

Condition

Specified Condition

A4-1 (E1) - Body ground

Always

Below 1 Ω

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (COOLING FAN ECU - BODY GROUND)

OK

7.

INSPECT FAN RELAY

(a) Inspect the FAN relay.

Click here

NG

REPLACE FAN RELAY

OK

8.

CHECK HARNESS AND CONNECTOR (FAN RELAY POWER SOURCE CIRCUIT)

(a) Remove the FAN relay from the No. 1 engine room relay block and No. 1 junction block assembly.

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

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

1 (FAN relay) - Body ground

Engine switch on (IG)

11 to 14 V

3 (FAN relay) - Body ground

Always

11 to 14 V

*1

No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly

*2

FAN Relay

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (FAN RELAY POWER SOURCE CIRCUIT)

OK

9.

CHECK HARNESS AND CONNECTOR (COOLING FAN ECU - FAN RELAY)

(a) Disconnect the A4 cooling fan ECU connector.

(b) Remove the FAN relay from the No. 1 engine room relay block and No. 1 junction block assembly.

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

Standard Resistance (Check for Open):

Tester Connection

Condition

Specified Condition

A4-3(+B1) - 5 (FAN relay)

Always

Below 1 Ω

Standard Resistance (Check for Short):

Tester Connection

Condition

Specified Condition

A4-3 (+B1) or 5 (FAN relay) - Body ground

Always

10 kΩ or higher

OK

REPAIR OR REPLACE HARNESS OR CONNECTOR (FAN RELAY - BODY GROUND)

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (COOLING FAN ECU - FAN RELAY)

10.

CHECK HARNESS AND CONNECTOR (ECM - COOLING FAN ECU)

(a) Disconnect the D2 ECM connector.

(b) Disconnect the A4 cooling fan ECU connector.

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

Standard Resistance (Check for Open):

Tester Connection

Condition

Specified Condition

D2-136 (RFC) - A4-2 (SI)

Always

Below 1 Ω

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (ECM - COOLING FAN ECU)

OK

11.

CHECK HARNESS AND CONNECTOR (COOLING FAN MOTOR LH - BODY GROUND)

(a) Disconnect the z2 cooling fan motor LH connector.

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

Standard Resistance (Check for Short):

Tester Connection

Condition

Specified Condition

z2-1 (M-) - Body ground

Always

10 kΩ or higher

*a

Component without harness connected

(Cooling Fan Motor LH)

NG

REPLACE COOLING FAN MOTOR LH

OK

12.

CHECK HARNESS AND CONNECTOR (COOLING FAN MOTOR RH - BODY GROUND)

(a) Disconnect the z1 cooling fan motor RH connector.

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

Standard Resistance (Check for Short):

Tester Connection

Condition

Specified Condition

z1-1 (M-) - Body ground

Always

10 kΩ or higher

*a

Component without harness connected

(Cooling Fan Motor RH)

OK

REPLACE COOLING FAN ECU

NG

REPLACE COOLING FAN MOTOR RH

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