Refer to
Cooling Fans
Circuit Description
Power is supplied to the cooling fan motors through a fusible link and three 60 amp maxifuses. The relay coils are energized when the PCM completes the ground path. The PCM Output Driver Module (ODM) B output 1 is grounded for Fan 1 operation. PCM ODM B output 2 is grounded for Fan 2 operation.
During Fan 1 operation the PCM supplies a ground path for the Fan 1 relay through ODM B output 1. This closes Fan 1 relay contacts and current flows from the battery junction block through the relay and to the primary cooling fan. The primary cooling fan is grounded at the engine block.
During Fan 2 operation the PCM keeps Fan 1 energized and supplies a ground path for the Fan 2 relay through ODM B output 2. This closes Fan 2 relay contacts and current flows through Fan 2 to engine ground.
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.
-
Stored Diagnostic Trouble Codes (That may not illuminate the Malfunction indicator Lamp) may enable the engine cooling fans. 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.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the On-Board Diagnostic (OBD) system check performed? | -- | ||
Are any PCM DTC(s) stored? | -- | Diagnose the applicable DTC(s) first. Refer to Powertrain Control Module Diagnosis | ||
3 |
Are the fans running? | -- | ||
4 | Select scan tool Misc. Tests, Output Controls function and command Fan 1 ON. Is Fan 1 ON? | -- | ||
5 | Select scan tool Misc. Tests, Output Controls function and command Fan 2 ON. Is Fan 2 ON? | -- | Refer to Diagnostic Aids | |
Is the test light ON? | -- | |||
7 | Check for a blown 60 AMP maxifuse #3. Is the fuse blown? | -- | ||
8 |
Is the test light ON? | -- | ||
9 | Locate and repair open battery feed circuit to cavity 30 in the Fan 1 relay connector. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
10 |
Is Fan 1 running? | -- | ||
11 |
Is the test light ON? | -- | ||
12 |
Is the test light ON? | -- | ||
13 | Locate and repair open in the Engine Cooling Fan Motor #1 feed circuit (CKT 409). Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
14 | Locate and repair open in the Engine Cooling Fan Motor #1 ground circuit (CKT 1050). Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
15 |
Is the test light ON | -- | ||
16 |
Is the test light ON? | -- | ||
17 | Locate and repair open in the battery feed circuit to cavity 85 in the Fan 1 relay connector. Is action complete? | -- | -- | |
18 | Locate and repair open in the coolant fan #1 relay control circuit. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
19 |
Is the test light ON? | -- | ||
20 | Locate and repair short to ground in the battery feed circuit to cavity 30 in the Fan Cont #1 relay connector. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
21 |
Is the test light ON? | -- | ||
22 | Locate and repair short to ground in the engine cooling fan motor #1 feed circuit (CKT 409). Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
23 |
Is the test light ON? | -- | ||
24 | Check the 60 AMP maxifuse that feeds Fan Cont #2 relay cavity 30. Is the fuse blown? | -- | ||
25 |
Is the test light ON? | -- | ||
26 | Locate and repair open feed circuit to Fan Cont #2 relay connector cavity 30. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
27 |
Is Fan 2 running? | -- | ||
28 |
Is the test light ON? | -- | ||
29 |
Is the test light ON? | -- | ||
30 | Locate and repair open in the engine cooling fan motor #2 feed circuit (CKT 504). Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
31 | Locate and repair open in the engine cooling Fan motor #2 ground circuit (CKT 1050). Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
32 | Check the fuse that feeds the Fan Cont #2 relay connector cavity 85. Is the fuse blown? | -- | ||
33 |
Is the test light ON? | -- | ||
34 | Locate and repair short to ground in the feed circuit to Fan Cont #2 relay connector cavity 85. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
35 | Probe cavity 85 in the Fan Cont #2 relay connector with a test light to ground. Is the test light ON | -- | ||
36 |
Is the test light ON? | -- | ||
37 | Locate and repair open in the feed circuit to Fan Cont #2 relay connector cavity 85. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
38 | Locate and repair open in the cooling fan #2 relay control circuit. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
39 |
Is the test light ON? | -- | ||
40 | Locate and repair short to ground in the feed circuit to Fan Cont #2 relay connector cavity 30. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
41 |
Is the test light ON? | -- | ||
42 | Locate and repair short to ground in the Engine Cooling Fan motor #2 feed circuit (CKT 504). Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
43 | Are both fans running? | -- | ||
44 |
Does the scan tool indicate A/C pressure at the specified value? | 0 V | ||
45 | Is Fan 1 running? | -- | ||
46 | Using scan tool monitor A/C Pressure. Does scan tool indicate A/C pressure greater than the specified value? | 1.98 V | ||
47 |
Is A/C pressure display at the specified value | 0 V | ||
48 | Locate and repair short to voltage in the Engine Cooling Fan motor #1 feed circuit (CKT 409). Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
49 | Replace the A/C Refrigerant Pressure sensor. Refer to On-Vehicle Service in Heating, Ventilation and Air Conditioning. Is action complete? | -- | -- | |
50 | Locate and repair short to voltage in the engine cooling Fan motor #2 feed circuit (CKT 504). Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
51 | Replace the PCM. Important: Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is action complete? | -- | -- | |
52 | Replace Engine Cooling Fan motor #1. Refer to On-Vehicle Service in Engine Cooling. Is action complete? | -- | -- | |
53 | Replace the Fan Control #1 relay. Is action complete? | -- | -- | |
54 | Replace Engine Cooling Fan motor #2. Refer to On-Vehicle Service in Engine Cooling. Is action complete? | -- | -- | |
55 | Replace the Fan Control #2 relay. Is action complete? | -- | -- | |
56 |
Are the Fans running? | -- | ||
57 | Select scan tool Misc. Tests, Output Controls function and command Fan 1 ON. Is Fan 1 running? | -- | ||
58 | Select scan tool Misc. Tests, Output Controls function and command Fan 2 ON. Is Fan 2 running? | -- | System OK |
