Circuit Description
During low speed operation, the engine coolant fans receive power from a 30 amp maxifuse. The PCM supplies a ground path for the Cool Fan 1 relay through the Coolant Fan #1 Relay Control circuit. This energizes the relay coil, closes the Fan 1 relay contacts, and supplies current to engine coolant fan motor #1. The ground path for cooling fan #1 is through the series/parallel cooling fan relay (Cool Fan 2 relay) and engine cooling fan motor #2. The result is a series circuit with both fans running at low speed.
During high speed fan operation, engine coolant fan motor #1 receives power from the 30 amp maxifuse. However, engine coolant fan motor #2 receives power from the 25 amp fan #3 fuse.
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 coolant fans have their 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
The numbers below refer to the step numbers 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 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||
Are any PCM DTCs stored? | -- | Diagnose the PCM DTCs first. | ||||||||
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 thecooling fan 1 running? | -- | ||||||||
11 | Remove the engine Cool Fan 2 from the Underhood Electrical Center. Is the cooling fan 1 running? | -- | ||||||||
12 | Locate and repair short to ground in CKT 532. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
13 |
Was a problem found? | -- | ||||||||
14 |
Is cooling fan 2 running? | -- | ||||||||
15 | Locate and repair the short to battery positive in circuit 532 or circuit 504. Did you complete the repair? | -- | -- | |||||||
16 |
Is the test lamp On? | -- | ||||||||
17 | Locate and repair the open in the Cool Fan 1 relay B+ feed to cavity 30. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
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 B+ feed to cavity 85 in the Cool Fan 1 relay connector. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
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. Did you complete the repair? | -- | -- | |||||||
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 CKT 409. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
36 | Using a test lamp connected to B+, probe Cool Fan 1 relay cavity 86. Is the test lamp On? | -- | ||||||||
37 | Replace Cool Fan 1 relay. Did you complete the repair? | -- | -- | |||||||
38 |
Is the test lamp On? | -- | ||||||||
39 | Locate and repair short to ground in the Low Speed Fans control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
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 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 DMM. Does the DMM display voltage near the specified value? | 0V | ||||||||
46 | Probe the A/C refrigerant pressure sensor ground with a 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 Condenser Replacement in HVAC Systems - Manual. Did you complete the repair? | -- | -- | |||||||
49 | Locate and repair open or short to voltage in the A/C refrigerant pressure sensor ground circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
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 in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
51 | Locate and repair short to voltage in the A/C refrigerant pressure signal circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
52 |
Is cooling fan 2 running at high speed? | -- | ||||||||
53 | Remove the Cool Fan 2 from the Underhood Electrical Center. Is cooling fan 2 running at high speed? | -- | ||||||||
54 | Locate and repair short to battery positive voltage in CKT 504. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
55 | Locate and repair short to battery positive voltage in CKT 532. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
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 cooling fan 1 connector with a test lamp to B+. Is the test lamp on? | -- | ||||||||
63 |
Did you complete the repair? | -- | -- | |||||||
64 |
Is the test lamp on? | -- | ||||||||
65 |
Did you complete the repair? | -- | -- | |||||||
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 in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
68 |
Was a problem found? | -- | ||||||||
69 |
Was a problem found? | -- | ||||||||
70 | Replace Cool Fan 3 relay. Did you complete the repair? | -- | -- | |||||||
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 in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
73 | Probe Cool Fan 2 cavity 87 in the Underhood Electrical Center with a test lamp to B+. 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 in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
75 |
Was a problem found? | -- | ||||||||
76 | Replace the Cool Fan 2 in the Underhood Electrical Center. Did you complete the repair? | -- | -- | |||||||
|
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the repair? | -- | -- | ||||||||
78 | Repair open in the Cool Fan 3 Relay control circuit . Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
79 | Replace the cooling fan 1 motor. Refer to Engine Cooling Fan Replacement in Engine Cooling. Did you complete the repair? | -- | -- | |||||||
80 | Replace the cooling fan 2 motor. Refer to Engine Cooling Fan Replacement in Engine Cooling. Did you complete the repair? | -- | -- | |||||||
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 |
