Circuit Description:
The engine coolant fan motor #1 receives power from a 40 amp MaxiFuse. The engine coolant fan motor #2 receives power from a 30 amp MaxiFuse. Both of the MaxiFuses are located in the underhood electrical center.
During low speed operation, the powertrain control module (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 the primary cooling fan. The ground path for the primary cooling fan is through the series/parallel cooling fan relay (cool fan 2 relay) and the secondary cooling fan 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 the primary and the secondary cooling fans are supplied current through their respective Maxifuses and each fan has a ground path.
Diagnostic Aids
Inspect for the following conditions:
| • | A faulty connection at the PCM, cooling fan relays, or cooling fan motors. Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connections. |
| • | Inspect the wiring harness for damage. |
Test Description
The 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 powertrain control module (PCM) enables the cooling fans due to A/C request. The PCM enables the cooling fans if the 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 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 powertrain control module (PCM) DTC(s) stored? | -- | Diagnose the PCM DTC(s) 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: The ambient temperature must be above 9°C (48°F).
Are the cooling fans on? | -- | Go to Diagnostic Aids | ||||||||
7 | View the A/C Request on the scan tool. Does the 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 left engine cooling fan running? | -- | ||||||||
11 | Remove the engine cool fan 2 relay from the underhood electrical center. Is the left engine cooling fan running? | -- | ||||||||
12 | Locate and repair a 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 the right engine cooling fan running? | -- | ||||||||
15 | Locate and repair the following circuit condition(s):
Did you complete the repair? | -- | -- | |||||||
16 |
Does the test lamp illuminate? | -- | ||||||||
17 | Locate and repair the open in the cool fan 1 relay battery positive feed to cavity 30. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
18 | Use a test lamp connected to ground in order to probe the cool fan 1 relay cavity 85. Does the test lamp illuminate? | -- | ||||||||
19 | Locate and repair open in the battery positive feed to cavity 85 in the cool fan 1 relay connector. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
20 |
Does the test lamp illuminate? | -- | ||||||||
21 |
Does the test lamp illuminate? | -- | ||||||||
22 |
Are both cooling fans running? | -- | ||||||||
23 |
Was a problem found? | -- | ||||||||
24 |
Was a problem found? | -- | ||||||||
25 |
Does the test lamp illuminate? | -- | ||||||||
26 | Locate and repair an open in the low speed fans control circuit between the PCM and the cool fan 1 relay cavity 86. Did you complete the repair? | -- | -- | |||||||
27 |
Does the test lamp illuminate? | -- | ||||||||
28 | Connect a test lamp between the cool fan 2 cavities 30 and 87A in the underhood electrical center. Does the test lamp illuminate? | -- | ||||||||
29 |
Was a problem found? | -- | ||||||||
30 |
Was a problem found? | -- | ||||||||
31 |
Was a problem found? | -- | ||||||||
32 | Use the scan tool in order to view the 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 the cool fan 1 relay from the underhood relay center. Are the cooling fans running? | -- | ||||||||
35 | Locate and repair a short to voltage in CKT 504. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
36 | Use a test lamp connected to battery positive voltage in order to probe the cool fan 1 relay cavity 86. Does the test lamp illuminate? | -- | ||||||||
37 | Replace the cool fan 1 relay. Did you complete the repair? | -- | -- | |||||||
38 |
Does the test lamp illuminate? | -- | ||||||||
39 | Locate and repair a 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 | Use the scan tool in order to view the A/C Pressure. Is the voltage less than the specified value? | 1.5 V | ||||||||
42 |
Is the right engine cooling fan running at high speed? | -- | ||||||||
43 |
Was a problem found? | -- | ||||||||
44 |
Is the voltage near the specified value? | 0 V | ||||||||
45 | Use a digital multimeter (DMM) in order to probe the A/C refrigerant pressure signal circuit. Is the voltage near the specified value? | 0 V | ||||||||
46 | Use a test lamp connected to B+ in order to probe the A/C refrigerant pressure sensor ground. Does the test lamp illuminate? | -- | ||||||||
47 | Use the DMM in order to probe the A/C refrigerant pressure sensor 5 volt reference B circuit. Is voltage near the specified value? | 5 V | ||||||||
48 | Replace the A/C refrigerant pressure sensor. Refer to A/C Refrigerant Pressure Sensor Replacement in HVAC System - Manual. Did you complete the repair? | -- | -- | |||||||
49 | Locate and repair an open or a 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 an open or a 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 a 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 the right engine cooling fan running at high speed? | -- | ||||||||
53 | Remove the cool fan 2 from the underhood electrical center. Is the right engine cooling fan running at high speed? | -- | ||||||||
54 | Locate and repair a short to battery positive voltage in CKT 409. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
55 | Locate and repair a 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 |
Does the test lamp illuminate? | -- | ||||||||
59 |
Does the test lamp illuminate? | -- | ||||||||
60 |
Was a problem found? | -- | ||||||||
61 |
Does the test lamp illuminate? | -- | ||||||||
62 | Use a test lamp connected to B+ in order to probe terminal A at the left engine cooling fan connector. Does the test lamp illuminate? | -- | ||||||||
63 |
Did you complete the repair? | -- | -- | |||||||
64 |
Does the test lamp illuminate? | -- | ||||||||
65 |
Did you complete the repair? | -- | -- | |||||||
66 | Use a test lamp connected to ground in order to probe the cool fan 3 relay cavity 30. Does the test lamp illuminate? | -- | ||||||||
67 | Locate and repair an open in the battery positive voltage circuit to the 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 the cool fan 3 relay. | -- | -- | |||||||
71 |
Does the test lamp illuminate? | -- | ||||||||
72 | Locate and repair an open in the B+ circuit to the cool fan 2 cavity 85. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
73 | Use a test lamp connected to B+ in order to probe the cool fan 2 cavity 87 in the underhood electrical center. Does the test lamp illuminate? | -- | ||||||||
74 | Locate and repair an open in the circuit between the 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 relay in the underhood electrical center. Did you complete the repair? | -- | -- | |||||||
|
Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming Replace the PCM. Did you complete the repair? | -- | -- | ||||||||
78 | Repair an open in the cool fan 3 relay control circuit . Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||
79 | Replace the left engine cooling fan motor. Did you complete the repair? | -- | -- | |||||||
80 | Replace the right engine cooling fan motor. 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 |
