Lexus NX manuals

Lexus NX: Cooling Fan Circuit

Lexus NX Service Manual / Engine & Hybrid System / 2ar-fxe (cooling) / Cooling Fan System / Cooling Fan Circuit

DESCRIPTION

The ECM calculates an appropriate cooling fan speed based on the engine coolant temperature, air conditioning switch condition, refrigerant pressure, hybrid coolant temperature, engine speed and vehicle speed, and sends the signals to the cooling fan ECU to regulate the cooling fans. The cooling fan ECU controls the cooling fan speed based on the duty ratio signal sent from the ECM. By basing its control on the operating conditions, the ECM can control the fan speed optimally using the cooling fan ECU, achieving both high cooling performance and quietness.

WIRING DIAGRAM

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CAUTION / NOTICE / HINT

NOTICE:

Inspect the fuses for circuits related to this system before performing the following procedure.

PROCEDURE

1.

PERFORM ACTIVE TEST USING TECHSTREAM (Control the Electric Cooling Fan)

(a) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Electric Cooling Fan.

(e) Check the operation of the cooling fans while operating them using the Techstream.

Powertrain > Engine and ECT > Active Test

Tester Display

Control the Electric Cooling Fan

OK:

Tester Operation

Fan Operation

ON

Cooling fans operate

OFF

Cooling fans stop

Result

Proceed to

OK

A

NG (Cooling fans do not operate)

B

NG (Cooling fans do not stop)

C

(f) Turn the power switch off.

A

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

C

GO TO STEP 11

B

2.

CHECK COOLING FAN SYSTEM

(a) Disconnect the A35 ECM connector.

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

(c) Check the operation of the cooling fans.

OK:

Cooling fans operate.

(d) Turn the power switch off.

(e) Reconnect the A35 ECM connector.

OK

REPLACE ECM

NG

3.

INSPECT COOLING FAN MOTOR (COOLING FAN MOTOR AND NO. 2 COOLING FAN MOTOR)

(a) Inspect the cooling fan motor and No. 2 cooling fan motor.

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Result

Proceed to

OK

A

NG (Cooling fan motor)

B

NG (No. 2 cooling fan motor)

C
B

REPLACE COOLING FAN MOTOR

C

REPLACE NO. 2 COOLING FAN MOTOR

A

4.

CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT)

(a) Disconnect the q1 cooling fan ECU connector.

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

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

q1-3 (B) - q1-1 (GND)

Power switch on (IG)

11 to 14 V

*a

Front view of wire harness connector

(to Cooling Fan ECU)

(d) Turn the power switch off.

(e) Reconnect the q1 cooling fan ECU connector.

NG

GO TO STEP 6

OK

5.

CHECK HARNESS AND CONNECTOR (ECM - COOLING FAN ECU)

(a) Disconnect the A35 ECM connector.

(b) Disconnect the q1 cooling fan ECU connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A35-44 (RFC) or q1-2 (SI) - Body ground

Always

10 kΩ or higher

(d) Reconnect the q1 cooling fan ECU connector.

(e) Reconnect the A35 ECM connector.

OK

REPLACE COOLING FAN ECU
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

6.

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

(a) Disconnect the q1 cooling fan ECU connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

q1-1 (GND) - Body ground

Always

Below 1 Ω

(c) Reconnect the q1 cooling fan ECU connector.

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

7.

INSPECT FAN NO.1 RELAY

(a) Inspect the FAN NO.1 relay.

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NG

REPLACE FAN NO.1 RELAY
OK

8.

INSPECT NO. 2 ENGINE ROOM RELAY BLOCK (FAN NO.1 RELAY)

(a) Remove the FAN NO.1 relay from the No. 2 engine room relay block.

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

3 (FAN NO.1 relay holder) - Body ground

Always

11 to 14 V

*1

No. 2 Engine Room Relay Block

*2

FAN NO.1 Relay

(c) Reinstall the FAN NO.1 relay.

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

9.

CHECK HARNESS AND CONNECTOR (COOLING FAN ECU - FAN NO.1 RELAY)

(a) Disconnect the q1 cooling fan ECU connector.

(b) Remove the FAN NO.1 relay from the No. 2 engine room relay block.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

q1-3 (B) - 5 (FAN NO.1 relay holder)

Always

Below 1 Ω

q1-3 (B) or 5 (FAN NO.1 relay holder) - Body ground

Always

10 kΩ or higher

(d) Reinstall the FAN NO.1 relay.

(e) Reconnect the q1 cooling fan ECU connector.

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

10.

CHECK HARNESS AND CONNECTOR (FAN NO.1 RELAY - BODY GROUND)

(a) Remove the FAN NO.1 relay from the No. 2 engine room relay block.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

2 (FAN NO.1 relay) - Body ground

Always

Below 1 Ω

(c) Reinstall the FAN NO.1 relay.

OK

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (FAN NO.1 RELAY - BODY GROUND)

11.

CHECK HARNESS AND CONNECTOR (ECM - COOLING FAN ECU)

(a) Disconnect the A35 ECM connector.

(b) Disconnect the q1 cooling fan ECU connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A35-44 (RFC) - q1-2 (SI)

Always

Below 1 Ω

(d) Reconnect the q1 cooling fan ECU connector.

(e) Reconnect the A35 ECM connector.

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

12.

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

(a) Disconnect the z1 cooling fan motor connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

z1-1 (-) - Body ground

Always

10 kΩ or higher

*a

Component without harness connected

(Cooling Fan Motor)

(c) Reconnect the z1 cooling fan motor connector.

NG

REPLACE COOLING FAN MOTOR

OK

13.

CHECK HARNESS AND CONNECTOR (NO. 2 COOLING FAN MOTOR - BODY GROUND)

(a) Disconnect the z9 No. 2 cooling fan motor connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

z9-1 (-) - Body ground

Always

10 kΩ or higher

*a

Component without harness connected

(No. 2 Cooling Fan Motor)

(c) Reconnect the z9 No. 2 cooling fan motor connector.

OK

REPLACE COOLING FAN ECU
NG

REPLACE NO. 2 COOLING FAN MOTOR

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