Refer to
Engine Cooling Fans
.
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.
-
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 Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Powertrain OBD System Check | |
Are any PCM DTC(s) stored? | -- | Go to applicable DTC table(s) | ||
3 |
Are the Fans OFF? | -- | ||
4 | Select scan tool Misc. Tests, Relay Control function and command Fan 1 ON. Is Fan 1 ON? | -- | ||
5 | Select scan tool Misc. Tests, Relay Control function and command Fan 2 ON. Is Fan 2 ON? | -- | Refer to Diagnostic Aids | |
Is the test light 'ON'? | -- | |||
7 | Check for a blown maxifuse. 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 Engine Electrical. 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. Refer to Engine Electrical. Is action complete? | -- | -- | |
14 | Locate and repair open in the Engine Cooling Fan Motor #1 ground circuit. Refer to Engine Electrical. 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 Fan 1 relay driver circuit. Refer to Engine Electrical. 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 Engine Electrical. 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. Refer to Engine Electrical. Is action complete? | -- | -- | |
23 |
Is the test light ON? | -- | ||
24 | Check for a blown 60 AMP maxifuse that feeds Fan 2 relay cavity 30. Is the fuse blown? | -- | ||
25 |
Is the test light ON? | -- | ||
26 | Locate and repair open in feed circuit to Fan 2 relay cavity 30. Refer to Engine Electrical. Is action complete? | -- | -- | |
27 |
Is Fan 2 ON? | -- | ||
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. Refer to Engine Electrical. Is action complete? | -- | -- | |
31 | Locate and repair open in the Engine Cooling Fan motor #2 ground circuit. Refer to Engine Electrical. 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 Engine Electrical. Is action complete? | -- | -- | |
35 | Probe cavity 85 in the Fan 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 2 relay connector cavity 85. Refer to Repair Procedures in Electrical Diagnosis Section 8A. Is action complete? | -- | -- | |
38 | Locate and repair open in the Fan 2 driver circuit. Refer to Engine Electrical. 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 30. Refer to Engine Electrical. 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. Refer to Repair Procedures in Electrical Diagnosis Section 8A. Is action complete? | -- | -- | |
43 | Are both fans ON? | -- | ||
44 |
Does scan tool indicate A/C pressure at the specified value? | 0 psi | ||
45 | Is Fan 1 ON? | -- | ||
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 | Locate and repair short to voltage in the Engine Cooling Fan motor #1 feed circuit. Refer to Engine Electrical. Is action complete? | -- | -- | |
49 | Replace the A/C Pressure sensor. Is action complete? | -- | -- | |
50 | Locate and repair short to voltage in the engine cooling Fan motor #2 feed circuit. Refer to Repair Procedures in Electrical Diagnosis Section 8A. Is action complete? | -- | -- | |
51 | Replace the PCM. Important: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is Action complete? | -- | -- | |
52 | Replace the Engine Cooling Fan motor #1 motor. Is action complete? | -- | -- | |
53 | Replace the Fan 1 relay Is action complete? | -- | -- | |
54 | Replace the Engine Cooling Fan motor #2. Is action complete? | -- | -- | |
55 | Replace the Fan 2 relay Is action complete? | -- | -- | |
56 |
Are the Fans OFF? | -- | ||
57 | Select scan tool Misc. Tests, Relay control function and command Fan 1 ON. Is Fan 1 ON? | -- | ||
58 | Select scan tool Misc. Tests, Relay control function and command Fan 2 ON. Is Fan 2 ON? | -- | System OK |
