Refer to Engine Controls Schematic
Cell 20: Cooling Fan Controls
Circuit Description:
The engine cooling fans receive power from two spearate 30 amp maxifuses located in the Underhood Electrical Center.
During low speed operation, the PCM supplies a ground path for the Cool Fan 1 relay through the Low Speed Fans Control circuit. This energizes the relay coil, closes the Fan 1 relay contacts, and supplies current to engine cooling fan #1 motor. The ground path for engine cooling fan #1 motor is through the series/parallel cooling fan relay (Cool Fan 2 relay) and engine cooling fan #2 motor. The result is a series circuit with both fans running at low speed.
To command high speed cooling fan operation the PCM first supplies a ground path for the Cool Fan 1 relay through the Low Speed Fans control circuit. After a 3 second delay, the PCM supplies a ground path for the Cool Fan 2 (series/parallel) and Cool Fan 3 relays through the High Speed Fans Control circuit. During high speed operation, both engine cooling fan motors are supplied current through their respective maxifuse and each fan has its own ground path.
The PCM will command Low Speed Cooling Fans operation under any of the following conditions:
VIN K
| • | When A/C is requested and ambient temperature is greater than 50°C (122°F). |
| • | When engine coolant temperature exceeds 106°C (223°F). |
| • | When A/C refrigerant pressure is greater than 190 psi (2 volts). |
| • | When the ignition is off and engine coolant temperature is greater than 140°C (284°F). |
VIN 1
| • | When A/C is requested and ambient temperature is greater than 40°C (104°F). |
| • | When engine coolant temperature exceeds 100°C (212°F). |
| • | When A/C refrigerant pressure is greater than 190 psi (2 volts). |
| • | When the ignition is off and engine coolant temperature is greater than 140°C (284°F). |
The PCM will command High Speed Cooling Fans operation under any of the following conditions:
VIN K
| • | When engine coolant temperature exceeds 110°C (230°F). |
| • | When A/C refrigerant pressure is greater than 240 psi (2.5 volts). |
VIN 1
| • | When engine coolant temperature exceeds 108°C (226°F). |
| • | When A/C refrigerant pressure is greater than 240 psi (2.5 volts). |
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.
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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.
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Ambient temperature must be above 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.
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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.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On--Board Diagnostic (OBD) System Check performed? | -- | ||||||||
Are any PCM DTCs stored? | -- | Go to Applicable DTCs | ||||||||
3 |
Are the cooling fans running? | -- | ||||||||
4 |
Are both cooling fans running at low speed? | -- | ||||||||
5 |
Are both fans running at high speed? | -- | ||||||||
|
Important: Ambient temperature must be above 9°C (48°F).
Are the cooling fans ON? | -- | Go to Diagnostic Aids | ||||||||
7 | View A/C Request on the scan tool. Does A/C Request on the scan tool display Yes? | -- | Go to Powertrain Control Module Controlled Air Conditioning (A/C) Circuit Diagnosis | |||||||
8 | Is either cooling fan running? | -- | ||||||||
9 | Is the left cooling fan running? | -- | ||||||||
10 |
Is the engine cooling fan 1 running? | -- | ||||||||
11 | Remove the engine Cool Fan 2 from the Underhood Electrical Center. Is the engine cooling fan 1 running? | -- | ||||||||
12 | Locate and repair short to ground in CKT 532. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||
13 |
Was a problem found? | -- | ||||||||
14 |
Is the engine cooling fan 2 running? | -- | ||||||||
15 | Locate and repair the short to battery positive in circuit 532 or circuit 504. Is action complete? | -- | -- | |||||||
16 |
Is the test lamp On? | -- | ||||||||
17 | Locate and repair the open in the Cool Fan 1 relay battery positive feed to cavity 30. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||
18 | Probe Cool Fan 1 relay cavity 85 with a test lamp connected to ground. Is the test lamp On? | -- | ||||||||
19 | Locate and repair open in the battery positive feed to cavity 85 in the Cool Fan 1 relay connector. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||
20 |
Is the test lamp ON? | -- | ||||||||
21 |
Is the test lamp ON? | -- | ||||||||
22 |
Are both cooling fans running? | -- | ||||||||
23 |
Was a problem found? | -- | ||||||||
24 |
Was a problem found? | -- | ||||||||
25 |
Is the test lamp ON? | -- | ||||||||
26 | Locate and repair open in the Low Speed Fans control circuit between the PCM and Cool Fan 1 relay cavity 86. Is action complete? | -- | -- | |||||||
27 |
Is the test lamp On? | -- | ||||||||
28 | Connect a test lamp between Cool Fan 2 cavities 30 and 87A in the Underhood Electrical Center. Is the test lamp ON? | -- | ||||||||
29 |
Was a problem found? | -- | ||||||||
30 |
Was a problem found? | -- | ||||||||
31 |
Was a problem found? | -- | ||||||||
32 | Using scan tool, view A/C Request. Does the scan tool display Yes? | -- | Go to Powertrain Control Module Controlled Air Conditioning (A/C) Circuit Diagnosis | |||||||
33 | Are both cooling fans running at low speed? | -- | ||||||||
34 | Remove Cool Fan 1 relay from the Underhood Relay Center. Are the cooling fans running? | -- | ||||||||
35 | Locate and repair short to voltage in KT 504. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||
36 | Using a test lamp connected to battery positive, probe Cool Fan 1 relay cavity 86. Is the test lamp On? | -- | ||||||||
37 | Replace Cool Fan 1 relay. Is action complete? | -- | -- | |||||||
38 |
Is the test lamp On? | -- | ||||||||
39 | Locate and repair short to ground in the Low Speed Fans control circuit. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||
40 | Are both cooling fans running at high speed? | -- | ||||||||
41 | View A/C Pressure on the scan tool. Does the scan tool display voltage less than the specified value? | 1.5V | ||||||||
42 |
Is the engine cooling fan 2 running at high speed? | -- | ||||||||
43 |
Was a problem found? | -- | ||||||||
44 |
Does the scan tool display voltage near the specified value? | 0V | ||||||||
45 | Probe the A/C refrigerant pressure signal circuit with a digital multimeter (DMM). Does the DMM display voltage near the specified value? | 0V | ||||||||
46 | Probe the A/C refrigerant pressure sensor ground with an unpowered test lamp to battery positive voltage. Is the test lamp on? | -- | ||||||||
47 | Probe the A/C refrigerant pressure sensor 5 volt reference B circuit with a DMM. Does the DMM display voltage near the specified value? | 5V | ||||||||
48 | Replace the A/C refrigerant pressure sensor. Refer to On-Vehicle Service in Heater, Ventilation, and Air Conditioning. Is action complete? | -- | -- | |||||||
49 | Locate and repair open or short to voltage in the A/C refrigerant pressure sensor ground circuit. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||
50 | Locate and repair open or short to ground in the A/C refrigerant pressure sensor 5 volt reference B circuit. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||
51 | Locate and repair short to voltage in the A/C refrigerant pressure signal circuit. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||
52 |
Is the engine cooling fan 2 running at high speed? | -- | ||||||||
53 | Remove the Cool Fan 2 from the Underhood Electrical Center. Is the engine cooling fan 2 running at high speed? | -- | ||||||||
54 | Locate and repair short to battery positive voltage in CKT 409. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||
55 | Locate and repair short to battery positive voltage in CKT 532. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||
56 |
Was a problem found? | -- | ||||||||
57 |
Was a problem found? | -- | ||||||||
58 |
Is the test lamp on? | -- | ||||||||
59 |
Is the test lamp ON? | -- | ||||||||
60 |
Was a problem found? | -- | ||||||||
61 |
Is the test lamp on? | -- | ||||||||
62 | Probe terminal A at the engine cooling fan 1 connector with a test lamp to battery positive. Is the test lamp on? | -- | ||||||||
63 |
Is action complete? | -- | -- | |||||||
64 |
Is the test lamp on? | -- | ||||||||
65 |
Is action complete? | -- | -- | |||||||
66 | Probe Cool Fan 3 relay cavity 30 with a test lamp connected to ground. Is the test lamp on? | -- | ||||||||
67 | Locate and repair open in battery positive voltage circuit to Cool Fan 3 relay cavity 30. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||
68 |
Was a problem found? | -- | ||||||||
69 |
Was a problem found? | -- | ||||||||
70 | Replace Cool Fan 3 relay. Is action complete? | -- | -- | |||||||
71 |
Is the test lamp on? | -- | ||||||||
72 | Locate and repair open in battery positive voltage circuit to Cool Fan 2 cavity 85. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||
73 | Probe Cool Fan 2 cavity 87 in the Underhood Electrical Center with a test lamp to battery positive. Is the test lamp on? | -- | ||||||||
74 | Locate and repair open in circuit between Cool Fan 2 cavity 87 in the Underhood Electrical Center and ground. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||
75 |
Was a problem found? | -- | ||||||||
76 | Replace the Cool Fan 2 in the Underhood Electrical Center. Is action complete? | -- | -- | |||||||
|
Important:: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is action complete? | -- | -- | ||||||||
78 | Repair open in the Cool Fan 3 Relay control circuit . Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||
79 | Replace the engine cooling fan 1 motor. Refer to On-Vehicle Service in Cooling and Radiator. Is action complete? | -- | -- | |||||||
80 | Replace the engine cooling fan 2 motor. Refer to On-Vehicle Service in Cooling and Radiator. Is action complete? | -- | -- | |||||||
81 |
Are the cooling fans running? | -- | ||||||||
82 |
Are both cooling fans running at low speed? | -- | ||||||||
83 |
Are both cooling fans running at high speed? | -- | System OK |
