Circuit Description
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 the relay contacts and current flows through the relay and to the 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 allowing current flow to Fan 2. Fan 2 is also grounded to the engine block.
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. 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 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 Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Powertrain OBD System Check | |
Are any DTC(s) stored? | -- | Go to applicable DTC(s) Table(s) | ||
3 |
Is Fan 1 ON? | -- | ||
4 | Select scan tool Misc. Tests, Relay Control function and command Fan 1 ON. Is Fan 1 ON? | -- | Refer to Diagnostic Aids | |
Is test light ON? | -- | |||
6 | Check for a blown fuse. Is fuse blown? | -- | ||
7 |
Is test light ON? | -- | ||
8 | Locate and repair open battery feed circuit in Fan 1 relay connector. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | Go to 29 | -- |
9 |
Is Fan 1 running? | -- | ||
10 |
Is the test light ON? | -- | Goto step 27 | |
11 |
Is the test light ON? | -- | ||
12 | Locate and repair open in Engine Cooling Fan Motor feed circuit. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
13 | Locate and repair open in the Engine Cooling Fan Motor Ground circuit. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
14 |
Is the test light ON | -- | ||
15 |
Is test light ON? | -- | ||
16 | Locate and repair open in the battery feed circuit to 85 in Fan 1 relay connector. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
17 | Locate and repair open in Fan 1 relay driver circuit. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
18 |
Is test light ON? | -- | ||
19 | Locate and repair short to ground in battery feed circuit to cavity 30 in Fan 1 relay connector. Refer to Repair Procedures in Electrical Diagnosis Section 8A. Is action complete? | -- | -- | |
20 |
Is test light ON? | -- | ||
21 | Locate and repair short to ground in Engine Cooling Fan Motor feed circuit. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
22 | Using scan tool monitor A/C pressure. Does scan tool indicate A/C pressure greater than the specified value? | 190 psi | ||
23 |
Is A/C pressure display at the specified value? | 0 psi | ||
24 | Locate and repair short to voltage in Engine Cooling Fan motor feed circuit. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |
25 | Replace A/C Pressure sensor. Is action complete? | -- | -- | |
26 | Replace PCM. Important: The replacement PCM must be programmed. Refer to PCM Replacement/Programming. Is action complete? | -- | -- | |
27 | Replace Engine Cooling Fan motor. Is action complete? | -- | -- | |
28 | Replace Fan 1 Relay. Is action complete? | -- | -- | |
29 |
Is Engine Cooling Fan OFF? | -- | System OK |
