Circuit Description:
Power for the fan motors is supplied through Maxi® Fuse 1 in the Engine wiring Harness Junction Block 1. The cooling fan relays are energized when current flows from the PCM Bat Fuse in the Engine Wiring Harness Junction Block 1 and Fan fuse in the Engine Wiring Harness Junction Block 2 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 cooling fan #1 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. This closes all three cooling fan relays. 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. Refer to Intermittents and Poor Connections Diagnosis and Connector Repairs and Wiring Repairs . |
| • | Damaged harness. Inspect the wiring harness for damage. Refer to Intermittents and Poor Connections Diagnosis and Connector Repairs and Wiring Repairs . |
Test Description
Numbers below refer to the step numbers on the Diagnostic Table:
-
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.
-
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.
-
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. Refer to Powertrain Control Module Replacement/Programming .
Step | Action | Values | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On Board Diagnostic (OBD) System Check performed? | -- | ||||||||||||||
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 Air Conditioning (A/C) Compressor Control 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 Fan 2 relay 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 in Wiring Systems. Is the action complete? | -- | -- | |||||||||||||
13 |
Was a problem found? | -- | ||||||||||||||
14 |
Is the right engine cooling fan running? | -- | ||||||||||||||
15 | Locate and repair short to battery positive voltage in circuit 532 and 504. If a problem is found repair as necessary. Refer to Wiring Repairs in Wiring Systems. Was a problem found? | -- | ||||||||||||||
16 |
Is the test light ON? | -- | ||||||||||||||
17 |
Is the action complete? | -- | -- | |||||||||||||
18 | Probe Cool Fan 1 relay cavity 85 with a test light connected to ground. Is the test light ON? | -- | ||||||||||||||
19 |
Blown fuse. If the fuse is blown, locate short circuit.
Is the 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 Coolant Fan 1 relay control circuit between the PCM and Cool Fan 1 relay cavity 86. Is the action complete? | -- | -- | |||||||||||||
27 |
Is the test light ON? | -- | ||||||||||||||
28 | Connect a test light between Fan 2 relay in Underhood Electrical Center cavities 30 and 87A. 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 Air Conditioning (A/C) Compressor Control Circuit Diagnosis | |||||||||||||
33 | Are both cooling fans running at low speed? | -- | ||||||||||||||
34 | Remove Cool Fan 1 relay from the Underhood Electrical Center. Are the cooling fans running? | -- | ||||||||||||||
35 | Locate and repair short to voltage in CKT 409. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||||||||
36 | Using a test light connected to battery positive voltage, probe Cool Fan 1 relay cavity 86. Is the test light ON? | -- | ||||||||||||||
37 | Replace Cool Fan 1 relay. Is the action complete? | -- | -- | |||||||||||||
38 |
Is the test light ON? | -- | ||||||||||||||
39 | Locate and repair short to ground in the Cool Fan 1 relay 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? | 1.2V | ||||||||||||||
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? | 0.0V | ||||||||||||||
45 | Probe the A/C refrigerant pressure signal circuit with a J 39200 connected to the A/C refrigerant pressure sensor ground. Does the digital multimeter display voltage near the specified value? | 0.0V | ||||||||||||||
46 | Probe the A/C refrigerant pressure sensor ground with a test light to battery positive voltage. Is the test light ON? | -- | ||||||||||||||
47 | Probe the A/C refrigerant pressure sensor 5 volt reference 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? | 5.0V | ||||||||||||||
48 | Replace the A/C refrigerant pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in HVAC System -- Manual. Is the action complete? | -- | -- | |||||||||||||
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. Is the action complete? | -- | -- | |||||||||||||
50 | Locate and repair open or short to ground in the A/C refrigerant pressure sensor 5 volt reference circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||||||||
51 | Locate and repair short to voltage in the A/C refrigerant pressure signal circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||||||||
52 |
Is the right engine cooling fan running at high speed? | -- | ||||||||||||||
53 | Remove the Fan 3 relay from the Underhood Electrical Center. Is the right engine cooling fan running at high speed? | -- | ||||||||||||||
54 | Locate and repair short to battery positive voltage in CKT 532. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||||||||
55 | Locate and repair short to battery positive voltage in CKT 504. Refer to Wiring Repairs in Wiring Systems. If a problem is found repair as necessary. Was a problem found? | -- | ||||||||||||||
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 at the left engine cooling fan connector with a test light to battery positive voltage. Is the test light ON? | -- | ||||||||||||||
63 |
Is the action complete? | -- | -- | |||||||||||||
64 |
Is the test light ON? | -- | ||||||||||||||
65 | Locate and repair the open in the ignition battery positive voltage circuit to the high speed engine cool fan 2 relay. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||||||||
66 | Probe Cool Fan 2 relay cavity 30 with a test light connected to ground. Is the test light ON? | -- | ||||||||||||||
67 | Locate and repair open in battery positive voltage circuit to Cool Fan 2 relay cavity 30. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||||||||
68 |
Was a problem found? | -- | ||||||||||||||
69 |
Was a problem found? | -- | ||||||||||||||
70 | Replace Cool Fan 2 relay. Is the action complete? | -- | -- | |||||||||||||
71 |
Is the test light ON? | -- | ||||||||||||||
72 | Locate and repair open in battery positive voltage circuit to Fan 3 relay cavity 85. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||||||||
73 | Probe Fan 3 relay cavity 87 in the Underhood Electrical Center with a test light to battery positive voltage. Is the test light ON? | -- | ||||||||||||||
74 | Locate and repair open in circuit between Fan 3 cavity 87 and Fan 2 relay cavity 87a in the Underhood Electrical Center and ground. Is the action complete? | -- | -- | |||||||||||||
75 |
Was a problem found? | -- | ||||||||||||||
76 | Replace the Fan 3 relay in the Underhood Electrical Center. Is the action complete? | -- | -- | |||||||||||||
|
Important: : The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||||||||||||||
78 | Repair open in the Cool Fan 2 relay cavity 86 and Cool relay cavity 86 control circuit to PCM. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||||||||
79 | Replace the left engine cooling fan motor. Refer to Engine Cooling Fan Replacement in HVAC System -- Manual. Did you complete the repair? | -- | -- | |||||||||||||
80 | Replace the right engine cooling fan motor. Refer to Engine Cooling Fan Replacement in HVAC System -- Manual. Is the 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 |
