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Makes 🢒 Chevrolet 🢒 2005 🢒 Aveo 🢒 Engine 🢒 Engine Cooling 🢒 Cooling Fan Circuit Diagnosis

Cooling Fan Circuit Diagnosis Single Fan

Circuit Description

The engine cooling fan circuit operates the cooling fan. The cooling fan is controlled by engine control module (ECM) based on input from the engine coolant temperature (ECT) sensor. The ECM controls the low speed cooling fan operation by providing a ground signal to the low speed fan relay. This energizes the low speed cooling fan relay and operates the cooling fan at low speed. The low speed cooling fan operation is achieved by the cooling fan resistor causing a drop in the voltage supplied to the cooling fan. The ECM controls the high speed cooling fan operation by providing a ground signal to the high speed fan relay. This energizes the high speed cooling fan relay, bypassing the radiator fan resistor. This results in high speed cooling fan operation.

Diagnostic Aids
    • If the owner complained of an overheating problem, it must be determined if the complaint was due to an actual boil over, or the engine coolant temperature gage indicated overheating. If the engine is overheating and the cooling fans are ON, the cooling system should be inspected.
    • If the I/P fuse block fuse F18 or the engine fuse block fuse EF3 or main relay fuse EF2 (1.2L only), become open, blown, immediately after installation, inspect for a short to ground in the wiring of the appropriate circuit. If the fuses become open, blown, when the cooling fan is to be turned ON by the ECM, suspect a faulty cooling fan motor.
    • The ECM will turn the cooling fans ON at low speed when the coolant temperature is 93°C (199°F). The ECM will turn the cooling fans OFF when the coolant temperature is 90°C (194°F).
    • The ECM will turn the cooling fans ON at high speed when the coolant temperature is 97°C (207°F). The ECM will change the cooling fans from high speed to low speed when the coolant temperature is 94°C (201°F).
    • The cooling fan circuit can be inspected quickly by disconnecting the ECM connector and grounding the low cooling fan control circuit. This should create low speed cooling fan operation with the ignition ON. By grounding the ECM low cooling fan relay and high cooling fan relay control circuits and turning the ignition ON, high speed cooling fan operation should be achieved.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step, along with step 5, checks for the ability of the ECM to operate the cooling fans.

    2.

  2. By directly grounding the ECM low cooling fan relay and high cooling fan relay control circuits, the cooling fan should run at high speed.

Step

Action

Yes

No

1

Did you perform the Diagnostic Starting Point - Engine Cooling?

Go to Step 2

Go to Diagnostic Starting Point - Engine Cooling

2
  1. Inspect the I/P fuse block fuse F18 for the 1.4L/1.5L application, or underhood fuse EF2 for the 1.2L.
  2. Replace the fuse as needed.

Is the fuse OK?

Go to Step 3

Go to Diagnostic Aids

3
  1. Inspect the engine fuse block fuse EF3.
  2. Replace the fuse as needed.

Is the fuse OK?

Go to Step 4

Go to Diagnostic Aids

4

  1. Turn the ignition OFF.
  2. Connect the scan tool to the data link connector (DLC).
  3. Start the engine.
  4. The cooling fan should run at low speed when the coolant temperature reaches 93°C (199°F).

Does the cooling fan run at low speed?

Go to Step 5

Go to Step 6

5
  1. Turn the ignition OFF.
  2. Connect a scan tool to the DLC.
  3. Start the engine.
  4. The cooling fan should run at high speed when the coolant temperature reaches 97°C (207°F).

Does the cooling fan run at high speed?

System OK

Go to Step 22

6
  1. Turn the ignition OFF.
  2. Disconnect the engine control module (ECM) connector.
  3. Connect a fused jumper between the ECM low cooling fan relay control circuit and ground.
  4. Turn the ignition ON.

Does the cooling fan run at low speed?

Go to Step 21

Go to Step 7

7
  1. Turn the ignition OFF.
  2. Connect a fused jumper between the ECM low cooling fan relay control circuit and ground.
  3. Disconnect the cooling fan connector.
  4. Connect a test light between the cooling fan connector terminal 2 and ground.
  5. Turn the ignition ON.

Is the test light ON?

Go to Step 8

Go to Step 9

8
  1. Turn the ignition OFF.
  2. Connect a test light between the cooling fan connector terminal 1 and battery positive.

Is the test light ON?

Go to Step 18

Go to Step 17

9
  1. Turn the ignition OFF.
  2. Remove the jumper from the ECM low cooling fan control circuit.
  3. Using a test light, connect to ground, probe the low speed relay connector terminal 86.
  4. Turn the ignition ON.

Is the test light ON?

Go to Step 10

Go to Step 13

10
  1. Turn the ignition OFF.
  2. Connect a test light between the cooling fan relay LOW connector terminal 30 and ground.

Is the test light ON?

Go to Step 11

Go to Step 14

11

Connect a test light between the cooling fan relay LOW connector terminal 87 and battery positive.

Is the test light ON?

Go to Step 12

Go to Step 16

12
  1. Connect a fused jumper between the ECM low cooling fan relay control circuit and ground.
  2. Connect a test light between the cooling fan relay LOW connector terminal 85 and battery positive.

Is the test light ON?

Go to Step 19

Go to Step 15

13

Repair the open wire between the cooling fan relay LOW connector terminal 85 and the ignition voltage supply.

Is the repair complete?

System OK

--

14

Repair the open wire between the cooling fan relay LOW connector terminal 30 and the fuse EF3.

Is the repair complete?

System OK

--

15

Repair the open wire between the cooling fan relay LOW connector terminal 86 and the ECM low cooling fan relay control circuit.

Is the repair complete?

System OK

--

16

Inspect for an open wire between the cooling fan relay LOW connector terminal 87 and the cooling fan connector terminal 2.

Is the problem found?

Go to Step 20

Go to Step 17

17

Inspect for an open wire between the cooling fan connector terminal 1 and ground.

Is the problem found?

Go to Step 20

Go to Step 18

18

Replace the cooling fan. Refer to Engine Cooling Fan Replacement .

Is the repair complete?

System OK

--

19

Replace the cooling fan relay LOW.

Is the repair complete?

System OK

--

20

Repair the wire as needed.

Is the repair complete?

System OK

--

21

Replace the ECM. Refer to the following:

    •  Engine Control Module Replacement in Engine Controls - 1.2L
    •  Engine Control Module Replacement in Engine Controls - 1.4L DOHC
    •  Engine Control Module Replacement in Engine Controls - 1.4L SOHC
    •  Engine Control Module Replacement in Engine Controls - 1.5L

Is the repair complete

System OK

--

22

  1. Turn the ignition OFF.
  2. Disconnect the ECM connector.
  3. Connect a fused jumper between the ECM low cooling fan relay control circuit and ground.
  4. Connect a fused jumper between the ECM high cooling fan relay control circuit and ground.
  5. Turn the ignition ON.

Does the cooling fan run at high speed?

Go to Step 21

Go to Step 23

23
  1. Turn the ignition OFF.
  2. Disconnect the cooling fan relay HI.
  3. Connect a test light between the cooling fan relay high connector terminal 85 and ground.
  4. Turn the ignition ON.

Is the test light ON?

Go to Step 24

Go to Step 28

24
  1. Turn the ignition OFF.
  2. Connect a test light between the cooling fan relay HI connector terminal 30 and ground.

Is the test light ON?

Go to Step 25

Go to Step 29

25

Connect a test light between the cooling fan relay HI connector terminal 87 and ground.

Is the test light ON?

Go to Step 26

Go to Step 30

26
  1. Connect a fused jumper between the ECM high cooling fan control circuit and ground.
  2. Connect a test light between the cooling fan relay HI connector terminal 86 and battery positive.

Is the test light ON?

Go to Step 27

Go to Step 31

27

Replace the cooling fan relay HI.

Is the repair complete?

System OK

--

28

Repair the open wire between the cooling fan relay HI connector terminal 85 and the ignition switch voltage supply.

Is the repair complete?

System OK

--

29

Repair the open wire between the cooling fan relay HI connector terminal 30 and the fuse EF3.

Is the repair complete?

System OK

--

30

Repair the open wire between the cooling fan relay HI connector terminal 87 and the cooling fan connector terminal 2.

Is the repair complete?

System OK

--

31

Repair the open wire between the cooling fan relay HI connector terminal 86 and the ECM relay control circuit.

Is the repair complete?

System OK

--

Cooling Fan Circuit Diagnosis Dual Fan

Circuit Description

Caution: Refer to Electric Coolant Fan Caution in the Preface section.

The engine cooling fan circuit operates the main cooling fan and the auxiliary cooling fan. The cooling fans are controlled by the engine control module (ECM) based on inputs from the engine coolant temperature (ECT) sensor and the air conditioning pressure (ACP) sensor. The ECM controls the low speed cooling fan operation by providing a ground signal to the low speed fan relay. This energizes the low speed cooling fan relay and operates the main cooling fan and the auxiliary cooling fan at low speed as the cooling fans are connected in a series circuit. The ECM controls the high speed cooling fan operation by providing a ground signal to the high speed cooling fan relay and the series/parallel relay a the same time. This energizes the low speed cooling fan relay, the high speed cooling fan relay, and the series/parallel cooling fan relay resulting in high speed fan operation as the cooling fans are now connected in a parallel circuit.

Diagnostic Aids
    • If the owner complained of an overheating problem, it must be determined if the complaint was due to an actual boil over, or the engine coolant temperature gage indicated overheating. If the engine is overheating and the cooling fans are ON, the cooling system should be inspected.
    • If the engine fuse block fuses EF3 become open, blown, immediately after installation, inspect for a short to ground in the wiring of the appropriate circuit. If the fuses become open, blown, when the cooling fans are to be turned ON by the ECM, suspect a faulty cooling fan motor.
    • The ECM will turn the cooling fans ON at low speed when the coolant temperature is 97°C (207°F). The ECM will turn the cooling fans OFF when the coolant temperature is 94°C (201°F).
    • The ECM will turn the cooling fans ON at high speed when the coolant temperature is 101°C (214°F). The ECM will change the cooling fans from high speed to low speed when the coolant temperature is 98°C (208°F).
    • The ECM will turn the cooling fans ON at low speed when the A/C system is ON. The ECM will change the cooling fans from low speed to high speed when the high side A/C pressure is 1882 kPa (273 psi), then return to low speed when the high side A/C pressure is 1448 kPa (210 psi). When the A/C system is ON, the ECM will change the cooling fans from low to high speed when the coolant temperature reaches 117°C (244°F), then return to low speed when the coolant temperature reaches 114°C (237°F).
    • The cooling fan circuit can be inspected quickly by disconnecting the ECM and ground the low speed relay control circuit. This should create low speed cooling fan operation with the ignition ON. By grounding the ECM low speed relay control circuit and the high speed relay control circuit and turning the ignition ON, high speed cooling fan operation should be achieved.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step, along with step 5, checks for the ability of the ECM to operate the cooling fans.

    2.

  2. This step, along with step 9, checks for the ability of the ECM to operate the cooling fans in response to A/C pressure readings.

    3.

  3. After confirming battery voltage and the ECM supplying a ground to the coil side of the cooling fan relay A, by jumpering connector terminals 30 and 87, it will be determined if the relay is at fault or a wiring problem is present.

    4.

  4. This step checks for the presence of battery voltage to the main cooling fan when the A/C is ON. If battery voltage is present and the cooling fans are not operating, the problem is in the ground side of the cooling fan circuit.

    5.

  5. By directly grounding the ECM low relay and high relay control circuits, the main and auxiliary cooling fans should run at high speed.

Step

Action

Yes

No

1

Did you perform the Diagnostic Starting Point - Engine Cooling?

Is the procedure completed?

Go to Step 2

Go to Diagnostic Starting Point - Engine Cooling

2
  1. Inspect the I/P engine block fuse EF3.
  2. Replace the fuse as needed.

Is the fuse OK?

Go to Step 3

Go to Diagnostic Aids

3
  1. Inspect the I/P fuse block fuse F18.
  2. Replace the fuse as needed.

Is the fuse OK?

Go to Step 4

Go to Diagnostic Aids

4

  1. Turn the ignition OFF.
  2. Turn the A/C switch OFF.
  3. Connect a scan tool to the data link connector (DLC).
  4. The cooling fans should run at low speed when the coolant temperature reaches 97°C (207°F).

Do the cooling fans run at low speed?

Go to Step 5

Go to Step 10

5
  1. Turn the ignition OFF.
  2. Turn the A/C switch OFF.
  3. Connect a scan tool to the DLC.
  4. Start the engine.
  5. The cooling fans should run at high speed when the coolant temperature reaches 101°C (214°F).

Do the cooling fans run at high speed?

Go to Step 6

Go to Step 33

6
  1. Turn the ignition OFF.
  2. Start the engine.
  3. Turn the A/C switch ON.

Does the A/C compressor clutch engage?

Go to Step 8

Go to Step 7

7
  1. Diagnose the A/C compressor clutch circuit.
  2. Repair the A/C compressor clutch circuit as needed.
  3. Start the engine.
  4. Turn the A/C switch ON.

Does the A/C compressor clutch engage?

Go to Step 8

--

8

Do the cooling fans run at low speed?

Go to Step 9

Go to Step 31

9
  1. Turn the ignition OFF.
  2. Connect the A/C pressure gages.
  3. Start the engine.
  4. Turn the A/C switch ON.
  5. The cooling fans should run at high speed when the high side A/C pressure reaches 1 882 kPa (273 psi).

Do the cooling fans run at high speed?

Go to Step 10

Go to DTC P0532 or P0533

10
  1. Turn the ignition OFF.
  2. Connect a scan tool to the DLC.
  3. The coolant temperature should be above 97°C (207°C).
  4. Disconnect the main cooling fan connector.
  5. Turn the ignition ON.
  6. Connect a test light between the main cooling fan connector terminal 2 and ground.

Is the test light ON?

Go to Step 11

Go to Step 12

11
  1. Turn the ignition OFF.
  2. Connect a scan tool to the DLC.
  3. The coolant temperature should be above 97°C (207°C).
  4. Disconnect the main cooling fan connector.
  5. Connect a test light between the main cooling fan connector terminal 1 and B+.

Is the test light ON?

Go to Step 28

Go to Step 17

12
  1. Turn the ignition OFF.
  2. Disconnect the cooling fan relay LOW.
  3. Connect a test light between the cooling fan relay LOW connector terminal 86 and ground.
  4. Turn the ignition ON.

Is the test light ON?

Go to Step 13

Go to Step 24

13
  1. Turn the ignition OFF.
  2. Connect the cooling fan relay LOW.
  3. Disconnect engine control module (ECM) white connector.
  4. Connect a fused jumper between the ECM low cooling fan relay control circuit and ground.
  5. Turn the ignition ON.

Do the cooling fans run at low speed?

Go to Step 30

Go to Step 14

14

Inspect for an open wire between the low speed cooling fan relay connector terminal 86 and the ECM low cooling fan relay control circuit.

Is the problem found?

Go to Step 25

Go to Step 15

15
  1. Turn the ignition OFF.
  2. Disconnect the cooling fan relay LOW.
  3. Connect a test light between the cooling fan relay LOW connector terminal 30 and ground.

Is the test light ON?

Go to Step 16

Go to Step 23

16

Connect a fused jumper between the cooling fan relay LOW connector terminals 30 and 87.

Do the cooling fans run at low speed?

Go to Step 26

Go to Step 17

17
  1. Disconnect the series/parallel fan series/parallel relay.
  2. Connect a fused jumper between the cooling fan relay LOW connector terminals 30 and 87.
  3. Connect a fused jumper between the cooling fan series/parallel relay connector terminals 30 and 87.

Do the cooling fans run at low speed?

Go to Step 27

Go to Step 18

18

Inspect the wire between the cooling fan relay LOW connector terminal 87 to the main cooling fan connector terminal 2 for an open.

Is the problem found?

Go to Step 22

Go to Step 19

19

Inspect the wire between the main cooling fan connector terminal 1 and the cooling fan control relay connector terminal 30 for an open.

Is the problem found?

Go to Step 22

Go to Step 20

20

Inspect the wire between the cooling fan series/parallel relay connector terminal 87A and the auxiliary cooling fan connector terminal 2 for an open.

Is the problem found?

Go to Step 22

Go to Step 21

21

Inspect for an open wire between the auxiliary cooling fan connector terminal 1 and ground.

Is the problem found?

Go to Step 22

Go to Step 29

22

Repair the open wire as needed.

Is the repair complete?

System OK

--

23

Repair the open between the cooling fan relay LOW connector terminal 30 and the fuse EF3.

Is the repair complete?

System OK

--

24

Repair the open between the cooling fan relay LOW connector terminal 85 and the ignition switch.

Is the repair complete?

System OK

--

25

Repair the open wire between the cooling fan relay LOW connector terminal 86 and the ECM low cooling fan relay control circuit.

Is the repair complete?

System OK

--

26

Replace the cooling fan relay LOW.

Is the repair complete?

System OK

--

27

Replace the cooling fan series/parallel relay.

Is the repair complete?

System OK

--

28

Replace the main cooling fan.

Is the repair complete?

System OK

--

29

Replace the auxiliary cooling fan.

Is the repair complete?

System OK

--

30

Replace the ECM. Refer to the following:

    •  Engine Control Module Replacement in Engine Controls - 1.2L
    •  Engine Control Module Replacement in Engine Controls - 1.4L DOHC
    •  Engine Control Module Replacement in Engine Controls - 1.4L SOHC
    •  Engine Control Module Replacement in Engine Controls - 1.5L
    •  Engine Control Module Replacement in Engine Controls - 1.6L (L91)

Is the repair complete?

System OK

--

31

  1. Turn the ignition OFF.
  2. Disconnect the main cooling fan connector.
  3. Connect a test light between the main cooling fan connector terminal 2 and ground.
  4. Turn the A/C switch ON.
  5. Start the engine.

Is the test light ON?

Go to Step 32

Go to Step 12

32
  1. Turn the ignition OFF.
  2. Connect a test light between the main cooling fan connector terminal 1 and battery positive.
  3. Turn the A/C switch ON.
  4. Start the engine.

Is the test light ON?

Go to Step 28

Go to Step 17

33
  1. Turn the ignition OFF.
  2. Disconnect the cooling fan relay HI.
  3. Connect a test light between the cooling fan relay HI connector terminal 85 and ground.
  4. Turn the ignition ON.

Is the test light ON?

Go to Step 34

Go to Step 44

34
  1. Turn the ignition OFF.
  2. Connect a test light between the cooling fan relay HI connector terminal 30 and ground.

Is the test light ON?

Go to Step 35

Go to Step 45

35
  1. Disconnect the cooling fan series/parallel relay.
  2. Connect a test light between the cooling fan series/parallel relay connector terminal 85 and ground.
  3. Turn the ignition ON.

Is the test light ON?

Go to Step 36

Go to Step 46

36
  1. Turn the ignition OFF.
  2. Connect a test light between the cooling fan series/parallel relay connector terminal 87 and battery positive.

Is the test light ON?

Go to Step 37

Go to Step 47

37

  1. Connect the main cooling fan connector.
  2. Connect the cooling fan relay HI.
  3. Connect the cooling fan series/parallel relay.
  4. Disconnect the ECM connector.
  5. Connect a fused jumper between the ECM low cooling fan relay control circuit and ground.
  6. Connect a fused jumper between the ECM high cooling fan relay control circuit and ground.
  7. Turn the ignition ON.

Do the cooling fans run at high speed?

Go to Step 30

Go to Step 38

38
  1. Turn the ignition OFF.
  2. Inspect for an open wire between the cooling fan relay HI connector terminal 86 and the ECM high cooling fan relay control circuit and ground.

Is the problem found?

Go to Step 22

Go to Step 39

39
  1. Disconnect the cooling fan relay HI.
  2. Connect a test light between the cooling fan relay HI connector terminal 87 and battery positive.

Is the test light ON?

Go to Step 40

Go to Step 48

40
  1. Disconnect the ECM connector.
  2. Connect a fused jumper between the ECM high cooling fan relay control circuit and ground.
  3. Disconnect the cooling fan relay HI.
  4. Connect a test light between the cooling fan control relay connector terminal 86 and battery positive.

Is the test light ON?

Go to Step 41

Go to Step 49

41
  1. Connect the cooling fan control relay.
  2. Connect a fused jumper between the ECM high cooling fan relay control circuit and ground.
  3. Disconnect the cooling fan relay HI.
  4. Connect a fused jumper between the cooling fan relay HI connector terminals 30 and 87.
  5. Disconnect the low speed cooling fan relay.
  6. Connect a fused jumper between the low speed cooling fan relay connector terminals 30 and 87.
  7. Turn the ignition ON.

Do the cooling fans run at high speed?

Go to Step 43

Go to Step 42

42
  1. Turn the ignition OFF.
  2. Connect a fused jumper between the ECM high cooling fan relay control circuit and ground.
  3. Disconnect the cooling fan series/parallel relay.
  4. Connect a fused jumper between the cooling fan series/parallel relay connector terminals 30 and 87.
  5. Connect a fused jumper between the low speed cooling fan relay connector terminals 30 and 87.
  6. Turn the ignition ON.

Do the cooling fans run at high speed?

Go to Step 27

--

43

Replace the cooling fan relay HI.

Is the repair complete?

System OK

--

44

Repair the open wire between the cooling fan relay HI connector terminal 85 and the ignition switch.

Is the repair complete?

System OK

--

45

Repair the open wire between the cooling fan relay HI connector terminal 30 and the battery.

Is the repair complete?

System OK

--

46

Repair the open wire between the cooling fan series/parallel relay connector terminal 85 and the ignition switch.

Is the repair complete?

System OK

--

47

Repair the open wire between the cooling fan series/parallel relay connector terminal 87 and ground.

Is the repair complete?

System OK

--

48

Repair the open wire between the cooling fan relay HI connector terminal 87 and the auxiliary cooling fan connector terminal 2.

Is the repair complete?

System OK

--

49

Repair the open wire between the cooling fan series/parallel relay connector terminal 85 and the ECM connector terminal K12.

Is the repair complete?

System OK

--