| Table 1: | Electric Cooling Fan Diagnosis (Oldsmobile) |
| Table 2: | Electric Cooling Fan Diagnosis (Chevrolet) |
Refer to
Coolant Fans (Oldsmobile)
.
Circuit Description
The cooling fan motors receive power from the following locations:
| • | Cooling Fan 1 receives power through the ECM BAT fuse and a 60 amp maxifuse located in the Underhood Electrical Center 1. |
| • | Cooling Fan 2 receiver power through the ECM IGN fuse and a 60 amp maxifuse located in the Underhood Electrical Center 1. |
During Fan 1 operation the PCM supplies a ground path for the Fan 1 relay through the Output Driver Module (ODM) B output 1. This closes Fan 1 relay contacts, energizes the relay coil and supplies current to the primary cooling fan.
During Fan 2 operation the PCM keeps Fan 1 energized and supplies a ground path for the Fan 2 relay through Output Driver Module (ODM) B output 2. This closes Fan 2 relay contacts, energizes the relay coil and supplies current to cooling Fan 2.
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? | -- | Go to A Powertrain On Board Diagnostic (OBD) System Check | |
Are any PCM DTC(s) stored? | -- | Diagnose the applicable DTC(s). Refer to Powertrain Control Module Diagnosis (PCM Diagnostic Trouble Codes) . | ||
3 |
Are the Fans OFF? | -- | ||
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 Fan 1 relay driver 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 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 2 relay cavity 30. Is the fuse blown? | -- | ||
25 |
Is the test light ON? | -- | ||
26 | Locate and repair open feed circuit to Fan 2 relay connector cavity 30. Refer to Repair Procedures in Electrical Diagnosis. 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 (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 Fan 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 2 relay connector cavity 85. Refer to Repair Procedures in Electrical Diagnosis. 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. Is action complete? | -- | -- | |
38 | Locate and repair open in the Fan 2 driver 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 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 ON? | -- | ||
44 |
Does scan tool indicate A/C pressure at the specified value? | 0V | ||
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? | 1.98V | ||
47 |
Is A/C pressure display at the specified value | 0V | ||
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. 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 PCM Replacement/Programming . Is Action complete? | -- | -- | |
52 | Replace the Engine Cooling Fan motor #1 motor. Refer to Engine Cooling System. Is action complete? | -- | -- | |
53 | Replace the Fan 1 relay Is action complete? | -- | -- | |
54 | Replace the Engine Cooling Fan motor #2. Refer to Engine Cooling System. Is action complete? | -- | -- | |
55 | Replace the Fan 2 relay Is action complete? | -- | -- | |
56 |
Are the Fans OFF? | -- | ||
57 | Select scan tool Misc. Tests, Output Controls function and command Fan 1 ON. Is Fan 1 ON? | -- | ||
58 | Select scan tool Misc. Tests, Output Controls function and command Fan 2 ON. Is Fan 2 ON? | -- | System OK |
Test Description
Number(s) below refer to the step number(s) 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.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||||
Are any PCM DTC(s) stored? | -- | Diagnose the PCM DTC(s) first. Refer to Powertrain Control Module Diagnosis | ||||||||
3 |
Are the cooling fan(s) 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 Powertrain Control Module Controlled Air Conditioning (A/C) 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 Control 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 Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||
13 |
Was a problem found? | -- | ||||||||
14 |
Is the right engine cooling fan running? | -- | ||||||||
15 | Replace the left engine cooling fan diode. Refer to Cooling Fans in Electrical Diagnosis. Is action complete? | -- | -- | |||||||
16 |
Is the test light On? | -- | ||||||||
17 | Locate and repair the open in the Fan Control 1 relay B+ feed to cavity 30. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||
18 | Probe Fan Control 1 relay cavity 85 with a test light connected to ground. Is the test light On? | -- | ||||||||
19 | Locate and repair open in the B+ feed to cavity 85 in the Fan Control 1 relay connector (CKT 540). Refer to Repair Procedures in Electrical Diagnosis. Is 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 Fan Control 1 relay control circuit between the PCM and Cooling Fan 1 relay cavity 86. Is action complete? | -- | -- | |||||||
27 |
Is the test light On? | -- | ||||||||
28 | Connect a test light between Fan Control 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 Powertrain Control Module Controlled Air Conditioning (A/C) Circuit Diagnosis | |||||||
33 | Are both cooling fan(s) running at low speed? | -- | ||||||||
34 | Remove Fan Control 1 relay from the Underhood Relay Center. Are the cooling fans running? | -- | ||||||||
35 | Locate and repair short to voltage in CKT 409. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||
36 | Using a test light connected to B+, probe Cooling Fan 1 relay cavity 86. Is the test light On? | -- | ||||||||
37 | Replace Fan Control 1 relay. Is action complete? | -- | -- | |||||||
38 |
Is the test light On? | -- | ||||||||
39 | Locate and repair short to ground in the Cooling Fan 1 relay control circuit. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||
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? | 1.5V | ||||||||
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? | 0V | ||||||||
45 | Probe the A/C refrigerant pressure signal circuit with a J 39200 Does the digital multimeter display voltage near the specified value? | 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 B circuit with a J 39200 Does the digital multimeter display voltage near the specified value? | 5V | ||||||||
48 | Replace the A/C refrigerant pressure sensor. Refer to On-Vehicle Service in Heater, Ventilation, and Air Conditioning. Is action complete? | -- | -- | |||||||
49 | Locate and repair open or short to voltage in the A/C refrigerant pressure sensor ground circuit. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||
50 | Locate and repair open or short to ground in the A/C refrigerant pressure sensor 5 volt reference B circuit. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||
51 | Locate and repair short to voltage in the A/C refrigerant pressure signal circuit. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||
52 |
Is the right engine cooling fan running at high speed? | -- | ||||||||
53 | Remove the Fan Control 2 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 504. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||
55 | Locate and repair short to battery positive voltage in CKT 532. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||
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 B+. Is the test light on? | -- | ||||||||
63 |
Is action complete? | -- | -- | |||||||
64 |
Is the test light on? | -- | ||||||||
65 | Locate and repair open in the ignition battery positive voltage circuit to high speed engine Cool Fan 2 relay. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||
66 | Probe Fan Control 3 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 Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||
68 |
Was a problem found? | -- | ||||||||
69 |
Was a problem found? | -- | ||||||||
70 | Replace Fan Control 3 relay. Is action complete? | -- | -- | |||||||
71 |
Is the test light on? | -- | ||||||||
72 | Locate and repair open in battery positive voltage circuit to Fan Control 2 relay cavity 85. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||
73 | Probe Fan Control 2 relay cavity 87 in the Underhood Electrical Center with a test light to B+. Is the test light on? | -- | ||||||||
74 | Locate and repair open in circuit between Fan Control 2 relay cavity 87 in the Underhood Electrical Center and ground. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||
75 |
Was a problem found? | -- | ||||||||
76 | Replace the Fan Control 2 relay in the Underhood Electrical Center. Is action complete? | -- | -- | |||||||
Replace the PCM. Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming Is action complete? | -- | -- | ||||||||
78 | Repair open in the control circuit to Fan Control 3 relay. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||
79 | Replace the left engine cooling fan motor. Refer to On-Vehicle Service in Cooling and Radiator. Is action complete? | -- | -- | |||||||
80 | Replace the right engine cooling fan motor. Refer to On-Vehicle Service in Cooling and Radiator. Is action complete? | -- | -- | |||||||
81 |
Observe the cooling fans. 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 |
