Circuit Description
Power is supplied to the cooling fan motors through fusible links. The relays are energized when the PCM completes the ground path to the relay coil . 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 through the relay and to the puller cooling fan. The puller cooling fan is grounded at the engine block. The PCM commands Fan 1 ON when engine coolant temperature increases above 108°C (226°F). Fan 1 will remain ON until the engine coolant temperature decreases below 103°C (217°F). The PCM also commands Fan 1 ON when A/C refrigerant pressure increases above 1310 kPa (190 psi). Fan 1 will remain ON until the A/C refrigerant pressure decreases below 807 kPa (117 psi).
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 to the pusher cooling fan. The pusher cooling fan is grounded at the chassis. The PCM commands Fan 2 ON when engine coolant temperature increases above 111°C (232°F). Fan 2 will remain ON until the engine coolant temperature decreases below 108°C (226°F). The PCM also commands Fan 2 ON when vehicle speed is below 77 km/h (48 mph) and A/C refrigerant pressure increases above 1655 kPa (240 psi). Fan 2 will remain ON until the A/C refrigerant pressure decreases below 1310 kPa (190 psi).
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
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Stored Diagnostic Trouble Codes (That may not illuminate the Malfunction indicator Lamp) may enable the engine cooling fans. Using chart C-12 may lead to improper diagnosis and replacement of good parts if Diagnostic Trouble Codes are present.
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Checks for cooling fan(s) ON all the time condition.
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Ensures that the PCM, Fan 1 relay, and related wiring can operate the puller fan properly.
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Ensures that the PCM, Fan 2 relay, and related wiring can operate the pusher fan properly.
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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. Refer to PCM Replacement and Programming Procedures in Powertrain Control Module (PCM) and Sensors.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to the Powertrain OBD System Check | |
Are any PCM DTC(s) stored? | -- | Go to applicable DTC table(s) | ||
Are both fans OFF? | -- | |||
Is the puller fan running? | -- | |||
Is the pusher fan running? | -- | Refer to Diagnostic Aids | ||
6 |
Is the test light ON? | -- | ||
7 | Check for a blown fusible link. Is the fusible link blown? | -- | ||
8 |
Is the test light ON? | -- | ||
9 | Locate and repair open battery feed circuit to cavity 87 in the Fan 1 relay connector (refer to Repair Procedures in Electrical Diagnosis Section 8A-5). Is action complete? | -- | -- | |
10 |
Is the puller fan running? | -- | ||
11 |
Is the test light ON? | -- | ||
12 |
Is the test light ON? | -- | ||
13 | Locate and repair open in the puller fan feed circuit (CKT 409) (refer to Repair Procedures in Electrical Diagnosis Section 8A-5). Is action complete? | -- | -- | |
14 | Locate and repair open in the puller fan ground circuit (CKT 1050) (refer to Repair Procedures in Electrical Diagnosis Section 8A-5). 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 harness connector. Is action complete? | -- | -- | |
18 | Locate and repair open in the Fan 1 relay driver circuit (refer to Repair Procedures in Electrical Diagnosis Section 8A-5). 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 1 relay connector (refer to Repair Procedures in Electrical Diagnosis Section 8A-5). Is action complete? | -- | -- | |
21 |
Is the test light ON? | -- | ||
22 | Locate and repair short to ground in the pusher fan feed circuit (CKT 409) (refer to Repair Procedures in Electrical Diagnosis Section 8A-5). Is action complete? | -- | -- | |
23 |
Is the test light ON? | -- | ||
24 | Check for a blown fusible link that feeds Fan 2 relay cavity 87. Is the fusible link blown? | -- | ||
25 |
Is the test light ON? | -- | ||
26 | Locate and repair open in feed circuit to Fan 2 relay cavity 87 (refer to Repair Procedures in Electrical Diagnosis Section 8A-5). Is action complete? | -- | -- | |
27 |
Is the pusher fan running? | -- | ||
28 |
Is the test light ON? | -- | ||
29 |
Is the test light ON? | -- | ||
30 | Locate and repair open in the pusher fan feed circuit (CKT 532)(refer to Repair Procedures in Electrical Diagnosis Section 8A-5). Is action complete? | -- | -- | |
31 | Locate and repair open in the pusher fan ground circuit (CKT 150) (refer to Repair Procedures in Electrical Diagnosis Section 8A-5). Is action complete? | -- | -- | |
32 | Check the fuse that feeds Fan 2 relay 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 2 relay cavity 85 (refer to Repair Procedures in Electrical Diagnosis Section 8A-5). Is action complete? | -- | -- | |
35 | Probe cavity 85 in the Fan 2 relay harness 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 2 relay connector cavity 85 (refer to Repair Procedures in Electrical Diagnosis Section 8A-5). Is action complete? | -- | -- | |
38 | Locate and repair open in the Fan 2 driver circuit (refer to Repair Procedures in Electrical Diagnosis Section 8A-5). Is action complete? | -- | -- | |
39 |
Is the test light ON? | -- | ||
40 | Locate and repair short to ground in the feed circuit to Fan 2 relay connector cavity 87 (refer to Repair Procedures in Electrical Diagnosis Section 8A-5). Is action complete? | -- | -- | |
41 |
Is the test light ON? | -- | ||
42 | Locate and repair short to ground in the pusher fan feed circuit (CKT 532) (refer to Repair Procedures in Electrical Diagnosis Section 8A-5). Is action complete? | -- | -- | |
43 | Are both fans running? | -- | ||
44 |
Does scan tool indicate A/C pressure at the specified value? | 0 psi | ||
45 | Is the puller fan running? | -- | ||
46 | Using scan tool monitor A/C Pressure. Does scan tool indicate A/C pressure greater than the specified value? | 190 psi | ||
47 |
Is A/C pressure display at the specified value? | 0 psi | ||
48 | Disconnect the Fan 1 relay electrical connector. Is the puller fan running? | |||
49 | Probe cavity 86 in the Fan 1 relay harness connector with a test light to B+. Is the test light ON? | |||
50 |
Is the test light ON? | |||
51 | Locate and repair short to ground in Fan 1 relay driver circuit (refer to Repair Procedures in Electrical Diagnosis Section 8A-5). Is Action complete? | -- | ||
52 | Locate and repair short to voltage in the puller fan feed circuit (CKT 409) (refer to Repair Procedures in Electrical Diagnosis Section 8A-5). Is action complete? | -- | -- | |
53 | Replace the A/C Pressure sensor. Is action complete? | -- | -- | |
54 | Disconnect the Fan 2 relay electrical connector. Is the puller fan ON? | |||
55 | Probe cavity 86 in the Fan 2 relay harness connector with a test light to B+. Is the test light ON? | |||
56 |
Is the test light ON? | |||
57 | Locate and repair short to ground in Fan 2 relay driver circuit (refer to Repair Procedures in Electrical Diagnosis Section 8A-5). Is Action complete? | -- | ||
58 | Locate and repair short to voltage in the pusher fan feed circuit (CKT 532) (refer to Repair Procedures in Electrical Diagnosis Section 8A-5). Is action complete? | -- | -- | |
Replace the PCM. Important: Replacement PCM must be programmed. Refer to On-Vehicle Service in Powertrain Control Module and Sensors for procedures. Is Action complete? | -- | -- | ||
60 | Replace the puller fan motor. Is action complete? | -- | -- | |
61 | Replace the Fan 1 relay Is action complete? | -- | -- | |
62 | Replace the pusher fan motor. Is action complete? | -- | -- | |
63 | Replace the Fan 2 relay Is action complete? | -- | -- | |
64 |
Are both fans OFF? | -- | ||
65 |
Is the puller fan running? | -- | ||
66 |
Is the pusher fan running? | -- | System OK |
