For 1990-2009 cars

### Circuit Description:

Power for the fan motors is supplied through a fusible link at the battery junction block. The cooling fan relays are energized when current flows from the A/P fan fuse through the relay coils to ground through the PCM. The cooling fan relay #1 control circuit is grounded for low speed fans operation. The cooling fan relay #1 control circuit and the cooling fan relay #2 and #3 circuits are both grounded for high speed fans operation.

During low speed fans operation the PCM supplies a ground path for the engine cooling fan relay #1. This closes the engine cooling fan relay #1 contacts, allowing current to flow from the battery junction block through the relay contacts to the left engine cooling fan. During low speed operation, the ground path for the left cooling fan is through the engine cooling fan relay #3 and the right engine cooling fan motor. The result is a series circuit with both cooling fans running at low speed.

During high speed cooling fan operation the PCM supplies a ground path for the engine cooling fan relay #1. The PCM also supplies a ground path for engine cooling fan relay #2 and engine cooling fan relay #3. For high speed cooling fans operation, the PCM will delay control of the cooling fan #2 and #3 relays for 6 seconds. The 6 second delay ensures that the cooling fan electrical load will not exceed the capacity of the system. During high speed fans operation, both the right and the left engine cooling fans are supplied current from the battery junction block and each cooling fan has its own ground path.

### Diagnostic Aids

Check for the following conditions:

• | Poor connection at the PCM, cooling fan relays, or cooling fan motors. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

• | Damaged harness. Inspect the wiring harness for damage.

### Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. Stored diagnostic trouble codes may affect engine cooling fans operation. This diagnostic table may lead to improper diagnosis and replacement of good parts if diagnostic trouble codes are present.

2. Ambient temperature must be greater than 9°C (48°F) before the PCM will enable the cooling fans due to A/C request. The PCM will enable the cooling fans if A/C refrigerant pressure increases regardless of ambient temperature.

3. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.

#### Electric Cooling Fan Diagnosis

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to the A Powertrain On Board Diagnostic (OBD) System Check
2 | Are any PCM DTC(s) stored? | -- | Diagnose the PCM DTC(s) first. Go to Powertrain Control Module Diagnosis (Powertrain DTCs) | Go to Step 3
3 |

1. Ensure that the engine coolant temperature is less than 100°C (212°F).
2. Turn the A/C OFF.
3. Engine running.
4. Observe the cooling fans.

Are the cooling fan(s) running?

--

Go to Step 32

Go to Step 4

4 |

1. Command Fan 1 ON using the scan tool output tests function.
2. Observe the cooling fans.

Are both cooling fans running at low speed?

--

Go to Step 5

Go to Step 8

5 |

1. Command Fan 2 ON using the scan tool output tests function.
2. Wait 6 seconds.
3. Observe the cooling fans

Are both fans running at high speed?

--

Go to Step 6

Go to Step 58

6 | Important:: Ambient temperature must be greater than 9°C (48°F).

1. Exit scan tool output tests.
2. Engine running.
3. Turn the A/C ON.

Are the cooling fans running?

--

Go to Diagnostic Aids

Go to Step 7

7 | View A/C Request on the scan tool. Does A/C Request on the scan tool display Yes? | -- | Go to Step 77 | Go to PCM Controlled A/C Circuit Diagnosis
8 | Is either cooling fan running? | -- | Go to Step 9 | Go to Step 16
9 | Is the left cooling fan running? | -- | Go to Step 10 | Go to Step 14
10 |

1. Turn OFF the ignition switch.
2. Disconnect the right engine cooling fan.
3. Turn ON the ignition switch.
4. Command Fan 1 ON using the scan tool output tests function.
5. Observe the cooling fans.

Is the left engine cooling fan running?

--

Go to Step 11

Go to Step 80

11 | Remove the series/parallel engine cooling fan relay #3 from the Underhood Electrical Center. Is the left engine cooling fan running? | -- | Go to Step 12 | Go to Step 13
12 | Locate and repair short to ground in CKT 532. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | Go to Step 81 | --
13 |

1. Check CKT 504 for a short to ground.
2. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 81

Go to Step 76

14 |

1. Turn OFF the ignition switch.
2. Disconnect the left engine cooling fan.
3. Turn ON the ignition switch.
4. Command Fan 1 ON using the scan tool output tests function.
5. Observe the cooling fans.

Is the right engine cooling fan running?

--

Go to Step 15

Go to Step 79

15 | Replace the left engine cooling fan diode. Refer to Cooling Fans in Electrical Diagnosis. Is action complete? | -- | Go to Step 81 | --
16 |

1. Ignition ON, engine not running.
2. Remove the low speed engine cooling fan relay #1 from the Underhood Electrical Center.
3. Probe Underhood Electrical Center cavity D1 with a test light connected to ground.

Is the test light ON?

--

Go to Step 18

Go to Step 17

17 |

1. Identify the cause of no battery positive voltage to Underhood Electrical Center cavity D1:

• | Blown fuse link. If the fuse link is blown, locate and correct short circuit.

- | Stalled right engine or left engine cooling fan.

- | Shorted right engine or left engine cooling fan motor windings.

- | Short to ground in CKT 402, CKT 532, or CKT 504.

• | Open in CKT 402.

2. Repair the cause of no battery positive voltage to Underhood Electrical Center cavity D1. Refer to Repair Procedures in Electrical Diagnosis.

Is action complete?

--

Go to Step 81

--

18 | Probe Underhood Electrical Center cavity D5 with a test light connected to ground. Is the test light ON? | -- | Go to Step 20 | Go to Step 19
19 |

1. Identify the cause of no battery positive voltage to Underhood Electrical Center cavity D5:

• | Blown fuse. If the fuse is blown, locate short circuit.

- | CKT 1440 shorted to ground.

- | Shorted low speed engine cooling fan relay #1 coil.

- | Shorted series/parallel engine cooling fan relay #3 coil.

- | Shorted high speed engine cooling fan relay #2 coil.

- | Circuit unrelated to cooling fans. Refer to Fuse Block Details in Electrical Diagnosis.

• | CKT 1440 open.

2. Repair cause of no battery positive voltage to Underhood Electrical Center cavity D5. Refer to Repair Procedures in Electrical Diagnosis.

Is action complete?

--

Go to Step 81

--

20 |

1. Turn OFF the ignition switch.
2. Disconnect both cooling fans.
3. Connect terminals A and B together at both cooling fan connectors using fused jumpers.
4. Turn ON the ignition switch.
5. Connect a test light between Underhood Electrical Center cavities D1 and D4.

Is the test light ON?

--

Go to Step 21

Go to Step 27

21 |

1. Connect a test light between Underhood Electrical Center cavities D2 and D5.
2. Turn ON the ignition switch.
3. Command Fan 1 ON using the scan tool output tests function.
4. Observe the test light.

Is the test light ON?

--

Go to Step 22

Go to Step 25

22 |

1. Turn OFF the ignition switch
2. Remove the jumpers from the engine cooling fan connectors and reconnect the cooling fans.
3. Install a fused jumper between Underhood Electrical Center cavities D1 and D4.
4. Turn ON the ignition switch.
5. Observe the cooling fans.

Are both cooling fans running?

--

Go to Step 23

Go to Step 24

23 |

1. Check for poor low speed engine cooling fan relay #1 connections at the Underhood Electrical Center.
2. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 81

Go to Step 37

24 |

1. Check for poor connections at the cooling fan motors.
2. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 81

Go to Step 63

25 |

1. Turn OFF the ignition switch.
2. Disconnect the PCM blue connector C1.
3. Install a fused jumper between Underhood Electrical Center cavities D1 and D2.
4. Turn ON the ignition switch.
5. Probe PCM harness connector cavity C1-32 with a test light to ground.

Is the test light ON?

--

Go to Step 77

Go to Step 26

26 | Locate and repair open in the cooling fan relay #1 control circuit (CKT 335) between the PCM and Underhood Electrical Center cavity D2. Is action complete? | -- | Go to Step 81 | --
27 |

1. Turn OFF the ignition switch.
2. Remove the jumpers from the cooling fan connectors.
3. Reconnect the cooling fans.
4. Install a fused jumper between Underhood Electrical Center cavities D1 and D4.
5. Remove the series/parallel engine cooling fan relay #3 from the Underhood Electrical Center.
6. Probe Underhood Electrical Center cavity J4 with a test light connected to ground.

Is the test light ON?

--

Go to Step 28

Go to Step 31

28 | Connect a test light between Underhood Electrical Center cavities J3 and J4. Is the test light ON? | -- | Go to Step 30 | Go to Step 29
29 |

1. Check for an open in CKT 504 between Underhood Electrical Center cavity J3 and right engine cooling fan terminal B.
2. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 81

Go to Step 57

30 |

1. Check for a poor connection at Underhood Relay Center cavities J3 or J4.
2. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 81

Go to Step 76

31 |

1. Check for an open in CKT 409 between Underhood Relay Center cavity D4 and left engine cooling fan harness connector terminal B.
2. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 81

Go to Step 56

32 | Using scan tool, view A/C Request. Does the scan tool display Yes? | -- | Go to PCM Controlled A/C Circuit Diagnosis | Go to Step 33
33 | Are both cooling fan(s) running at low speed? | -- | Go to Step 34 | Go to Step 40
34 | Remove low speed engine cooling fan relay #1 from the Underhood Relay Center. Are the cooling fans running? | -- | Go to Step 35 | Go to Step 36
35 | Locate and repair short to voltage in CKT 409. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | Go to Step 81 | --
36 | Using a test light connected to B+, probe Underhood Relay Center cavity D2. Is the test light ON? | -- | Go to Step 38 | Go to Step 37
37 | Replace low speed engine cooling fan relay #1. Is action complete? | -- | Go to Step 81 | --
38 |

1. Turn OFF the ignition switch
2. Disconnect the blue PCM connector C1.
3. Probe Underhood Relay Center cavity D2 with a test light connected to B+.

Is the test light ON?

--

Go to Step 39

Go to Step 77

39 | Locate and repair short to ground in the cooling fan relay #1 control circuit (CKT 335). Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | Go to Step 81 | --
40 | Are both cooling fans running at high speed? | -- | Go to Step 41 | Go to Step 42
41 | View A/C Pressure on the scan tool. Does the scan tool display voltage less than the specified value? | 1.2V | Go to Step 77 | Go to Step 44
42 |

1. Turn OFF the ignition switch.
2. Disconnect the PCM.
3. Turn ON the ignition switch.
4. Observe the cooling fans.

Is the right engine cooling fan running at high speed?

--

Go to Step 43

Go to Step 77

43 |

1. Check for a short to ground in the cooling fan #2 and #3 control circuit (CKT 473).
2. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 81

Go to Step 52

44 |

1. Turn OFF the ignition switch.
2. Disconnect the A/C refrigerant pressure sensor electrical connector.
3. Turn ON the ignition switch.
4. View A/C Pressure on the scan tool.

Does the scan tool display voltage near the specified value?

0V

Go to Step 46

Go to Step 45

45 | Probe the A/C refrigerant pressure signal circuit with a J 39200 Digital Multimeter connected to the A/C refrigerant pressure sensor ground. Does the digital multimeter display voltage near the specified value? | 0V | Go to Step 77 | Go to Step 51
46 | Probe the A/C refrigerant pressure sensor ground with a test light to B+. Is the test light ON? | -- | Go to Step 47 | Go to Step 49
47 | Probe the A/C refrigerant pressure sensor 5 volt reference circuit B with aJ 39200 Digital Multimeter connected to the A/C refrigerant pressure sensor ground. Does the digital multimeter display voltage near the specified value? | 5V | Go to Step 48 | Go to Step 50
48 | Replace the A/C refrigerant pressure sensor. Refer to On-Vehicle Service in Heater, Ventilation, and Air Conditioning. Is action complete? | -- | Go to Step 81 | --
49 | Locate and repair open or short to voltage in the A/C refrigerant pressure sensor ground circuit. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | Go to Step 81 | --
50 | Locate and repair open or short to ground in the A/C refrigerant pressure sensor 5 volt reference B circuit. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | Go to Step 81 | --
51 | Locate and repair short to voltage in the A/C refrigerant pressure signal circuit. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | Go to Step 81 | --
52 |

1. Remove the high speed engine cooling fan relay #2 from the Underhood Electrical Center.
2. Observe the cooling fans.

Is the right engine cooling fan running at high speed?

--

Go to Step 53

Go to Step 70

53 | Remove series/parallel engine cooling fan relay #3 from the Underhood Electrical Center. Is the right engine cooling fan running at high speed? | -- | Go to Step 54 | Go to Step 55
54 | Locate and repair short to B+ in CKT 504. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | Go to Step 81 | --
55 | Locate and repair short to B+ in CKT 532. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | Go to Step 81 | --
56 |

1. Check for an open in CKT 532 between Underhood Electrical Center cavity J4 and left engine cooling fan terminal A.
2. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 81

Go to Step 79

57 |

1. Check for an open in CKT 150 between right engine cooling fan terminal A and ground.
2. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 81

Go to Step 80

58 |

1. Ignition ON, engine not running.
2. Remove the high speed engine cooling fan relay #2 from the Underhood Electrical Center.
3. Install a test light between Underhood Electrical Center cavity F2 and B+.
4. Command Fan 2 ON using the scan tool output controls function.
5. Wait 6 seconds.
6. Observe the test light.

Is the test light ON?

--

Go to Step 61

Go to Step 59

59 |

1. Remove the series/parallel engine cooling fan relay #3 from the Underhood Electrical Center.
2. Install a test light between Underhood Electrical Center cavity J2 and B+.
3. Command Fan 2 ON using the scan tool output controls function.
4. Wait 6 seconds.
5. Observe the test light.

Is the test light ON?

--

Go to Step 78

Go to Step 60

60 |

1. Turn OFF the ignition switch.
2. Disconnect the PCM.
3. Turn ON the ignition switch.
4. Check the cooling fan relay #2 and #3 control circuit (CKT 473) for an open or a short to voltage between Underhood Electrical Center cavity J2 and the PCM.
5. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 81

Go to Step 77

61 |

1. Turn OFF the ignition switch
2. Reinstall high speed engine cooling fan relay #2.
3. Disconnect both cooling fan electrical connectors.
4. Turn ON the ignition switch.
5. Command Fan 2 ON using the scan tool output controls function.
6. Wait 6 seconds.
7. Probe terminal B (CKT 504) at the right engine cooling fan connector with a test light to ground.

Is the test light ON?

--

Go to Step 62

Go to Step 64

62 | Probe terminal A (CKT 532) at the left engine cooling fan connector with a test light to B+. Is the test light ON? | -- | Go to Step 63 | Go to Step 71
63 |

1. Identify cause of inoperative cooling fan:

• | Open right engine cooling fan motor windings.

• | Open left engine cooling fan motor windings.

• | Stalled cooling fan(s).

2. Replace the affected cooling fan motor. Refer to On-Vehicle Service in Cooling and Radiator.

Is action complete?

--

Go to Step 81

--

64 |

1. Remove the high speed engine cooling fan relay #2 from the Underhood Electrical Center.
2. Turn ON the ignition switch.
3. Probe Underhood Electrical Center cavity F5 with a test light connected to ground.

Is the test light ON?

--

Go to Step 66

Go to Step 65

65 | Locate and repair open in the ignition positive voltage circuit to high speed engine cooling fan relay #2. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | Go to Step 81 | --
66 | Probe Underhood Electrical Center F4 with a test light connected to ground. Is the test light ON? | -- | Go to Step 68 | Go to Step 67
67 | Locate and repair open in battery positive voltage circuit to Underhood Electrical Center cavity F4. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | Go to Step 81 | --
68 |

1. Check CKT 504 for an open between right engine cooling fan terminal B and Underhood Electrical Center cavity F1.
2. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 81

Go to Step 69

69 |

1. Check for poor high speed engine cooling fan relay #2 terminal connections at the Underhood Electrical Center.
2. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 81

Go to Step 70

70 | Replace high speed engine cooling fan relay #2. Is action complete? | -- | Go to Step 81 | --
71 |

1. Remove the series/parallel cooling #3 fan relay from the Underhood Electrical Center.
2. Turn ON the ignition switch.
3. Probe Underhood Electrical Center cavity J5 with a test light connected to ground.

Is the test light ON?

--

Go to Step 73

Go to Step 72

72 | Locate and repair open in battery positive voltage circuit to Underhood Electrical Center cavity J5. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | Go to Step 81 | --
73 | Probe Underhood Electrical Center cavity J1 with a test light to B+. Is the test light ON? | -- | Go to Step 75 | Go to Step 74
74 | Locate and repair open in CKT 150 between Underhood Electrical Center cavity J1 and ground. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | Go to Step 81 | --
75 |

1. Check for poor series/parallel engine cooling fan relay #3 terminal connections at the Underhood Electrical Center.
2. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 81

Go to Step 76

76 | Replace the series/parallel engine cooling fan relay #3. Is action complete? | -- | Go to Step 81 | --
77 | Replace the PCM. Important:: The replacement PCM must be programmed. Refer to PCM Replacement/Programming . Is action complete? | -- | Go to Step 81 | --
78 | Repair open in the cooling fan relay #2 and #3 control circuit (CKT 473) to Underhood Electrical Center cavity F2. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | Go to Step 81 | --
79 | Replace the left engine cooling fan motor. Refer to On-Vehicle Service in Cooling and Radiator. Is action complete? | -- | Go to Step 81 | --
80 | Replace the right engine cooling fan motor. Refer to On-Vehicle Service in Cooling and Radiator. Is action complete? | -- | Go to Step 81 | --
81 |

1. Engine coolant less than 100°C (212°F).
2. Ensure that the A/C is OFF.
3. Engine running.

Observe the cooling fans.

Are the cooling fans running?

--

Go to Step 32

Go to Step 82

82 |

1. Command Fan 1 ON using the scan tool output tests function.
2. Observe the cooling fans.

Are both cooling fans running at low speed?

--

Go to Step 83

Go to Step 8

83 |

1. Command Fan 2 ON using the scan tool output tests function.
2. Wait 6 seconds.
3. Observe the cooling fans.

Are both cooling fans running at high speed?

--

System OK

Go to Step 58