Circuit Description:
Power for the fan motors is supplied through a 40 amp MaxiFuse® located in the Underhood Fuse Block. The cooling fan relays receive power from a 25 amp fuse located in the Underhood Fuse Block.
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 40 amp Maxifuse®, through the relay contacts, and 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. After a 6 second delay, the PCM supplies a ground path for engine cooling fan relay #2 and engine cooling fan relay #3. 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 engine cooling fans are supplied current from the 40 amp Maxifuse® and each cooling fan has its own ground path.
Diagnostic Aids
The PCM will complete the ground path for cooling fan relay #1 under any of the following conditions:
| • | When engine coolant temperature exceeds 105°C (221°F). |
| • | When A/C is requested and ambient temperature is greater than 10°C (50°F). |
| • | When A/C refrigerant pressure is greater than 190 psi (2 volts). |
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. The PCM will complete the ground paths for cooling fan relays #1, #2, and #3 under any of the following conditions:
| • | When engine coolant temperature exceeds 113°C (235°F). |
| • | When A/C refrigerant pressure is greater than 275 psi (2.9 volts). |
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 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.
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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 powertrain DTCs stored? | -- | Diagnose the DTCs first. | ||||||||||||||||
3 |
Are the cooling fan(s) running? | -- | ||||||||||||||||
4 |
Are both cooling fans running at low speed? | -- | ||||||||||||||||
5 |
Are both fans running at high speed? | -- | ||||||||||||||||
|
Important:: Ambient temperature must be greater than 9°C (48°F).
Are the cooling fans running? | -- | 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 left engine cooling fan running? | -- | ||||||||||||||||
11 | Remove the series/parallel engine cooling fan relay #3 from the Underhood Electrical Center. Is the left engine cooling fan 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 right engine cooling fan running? | -- | ||||||||||||||||
15 | Replace the left engine cooling fan diode. Is action complete? | -- | -- | |||||||||||||||
16 |
Is the test light ON? | -- | ||||||||||||||||
17 |
Is action complete? | -- | -- | |||||||||||||||
18 | Probe Underhood Electrical Center cavity D5 with a test light connected to ground. Is the test light ON? | -- | ||||||||||||||||
19 |
Is action complete? | -- | -- | |||||||||||||||
20 |
Is the test light ON? | -- | ||||||||||||||||
21 |
Is the test light ON? | -- | ||||||||||||||||
22 |
Are both cooling fans running? | -- | ||||||||||||||||
23 |
Was a problem found? | -- | ||||||||||||||||
24 |
Was a problem found? | -- | ||||||||||||||||
25 |
Is the test light ON? | -- | ||||||||||||||||
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? | -- | -- | |||||||||||||||
27 |
Is the test light ON? | -- | ||||||||||||||||
28 | Connect a test light between Underhood Electrical Center cavities J3 and J4. Is the test light 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 fan(s) running at low speed? | -- | ||||||||||||||||
34 | Remove low speed engine cooling fan relay #1 from the Underhood Relay Center. Are the cooling fans running? | -- | ||||||||||||||||
35 | Locate and repair short to voltage in CKT 409. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||||||||||
36 | Using a test light connected to B+, probe Underhood Relay Center cavity D2. Is the test light ON? | -- | ||||||||||||||||
37 | Replace low speed engine cooling fan relay #1. Is action complete? | -- | -- | |||||||||||||||
38 |
Is the test light ON? | -- | ||||||||||||||||
39 | Locate and repair short to ground in the cooling fan relay #1 control circuit (CKT 335). 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? | 1.2V | ||||||||||||||||
42 |
Is the right engine cooling fan 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 J 39200 Digital Multimeter connected to the A/C refrigerant pressure sensor ground. Does the digital multimeter display voltage near the specified value? | 0V | ||||||||||||||||
46 | Probe the A/C refrigerant pressure sensor ground with a test light to B+. Is the test light ON? | -- | ||||||||||||||||
47 | Probe the A/C refrigerant pressure sensor 5 volt reference circuit B 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? | 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 right engine cooling fan running at high speed? | -- | ||||||||||||||||
53 | Remove series/parallel engine cooling fan relay #3 from the Underhood Electrical Center. Is the right engine cooling fan running at high speed? | -- | ||||||||||||||||
54 | Locate and repair short to B+ in CKT 504. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||||||||||
55 | Locate and repair short to B+ in CKT 532. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||||||||||
56 |
Was a problem found? | -- | ||||||||||||||||
57 |
Was a problem found? | -- | ||||||||||||||||
58 |
Is the test light ON? | -- | ||||||||||||||||
59 |
Is the test light ON? | -- | ||||||||||||||||
60 |
Was a problem found? | -- | ||||||||||||||||
61 |
Is the test light ON? | -- | ||||||||||||||||
62 | Probe terminal A (CKT 532) at the left engine cooling fan connector with a test light to B+. Is the test light ON? | -- | ||||||||||||||||
63 |
Is action complete? | -- | -- | |||||||||||||||
64 |
Is the test light ON? | -- | ||||||||||||||||
65 | Locate and repair open in the ignition positive voltage circuit to high speed engine cooling fan relay #2. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||||||||||
66 | Probe Underhood Electrical Center F4 with a test light connected to ground. Is the test light ON? | -- | ||||||||||||||||
67 | Locate and repair open in battery positive voltage circuit to Underhood Electrical Center cavity F4. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||||||||||
68 |
Was a problem found? | -- | ||||||||||||||||
69 |
Was a problem found? | -- | ||||||||||||||||
70 | Replace high speed engine cooling fan relay #2. Is action complete? | -- | -- | |||||||||||||||
71 |
Is the test light ON? | -- | ||||||||||||||||
72 | Locate and repair open in battery positive voltage circuit to Underhood Electrical Center cavity J5. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||||||||||
73 | Probe Underhood Electrical Center cavity J1 with a test light to B+. Is the test light ON? | -- | ||||||||||||||||
74 | Locate and repair open in CKT 150 between Underhood Electrical Center cavity J1 and ground. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||||||||||
75 |
Was a problem found? | -- | ||||||||||||||||
76 | Replace the series/parallel engine cooling fan relay #3. Is action complete? | -- | -- | |||||||||||||||
Replace the PCM. Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is action complete? | -- | -- | ||||||||||||||||
78 | Repair open in the cooling fan relay #2 and #3 control circuit (CKT 473) to Underhood Electrical Center cavity F2. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||||||||||
79 | Replace the left engine cooling fan motor. Refer to On-Vehicle Service in Cooling and Radiator. Is action complete? | -- | -- | |||||||||||||||
80 | Replace the right engine cooling fan motor. Refer to On-Vehicle Service in Cooling and Radiator. Is action complete? | -- | -- | |||||||||||||||
81 |
Observe the cooling fans. Are the cooling fan(s) running? | -- | ||||||||||||||||
82 |
Are both cooling fans running at low speed? | -- | ||||||||||||||||
83 |
Are both cooling fans running at high speed? | -- | System OK |
