Electric Cooling Fan Diagnosis Oldsmobile Only
Refer to
Coolant Fans (Oldsmobile)
.
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? | -- | ||
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 |
Electric Cooling Fan Diagnosis Chevrolet Only
Refer to
Coolant Fans (Chevrolet)
Circuit Description:
Power for the fan motors is supplied through a fusible link at the battery junction block. The cooling fan relays are energized when current flows from the PCM Bat Fuse in the Underhood Electrical Center #1 and Fan fuse in the Underhood Electrical Center #2 through the relay coils to ground through the PCM. The cooling fan relay #1 control circuit is grounded for low speed fans operation. The cooling fan relay #1 control circuit and the cooling fan relay #2 and #3 circuits are both grounded for high speed fans operation.
During low speed fans operation the PCM supplies a ground path for the engine cooling fan relay #1. This closes the engine cooling fan relay #1 contacts, allowing current to flow from the battery junction block through the relay contacts to the left engine cooling fan. During low speed operation, the ground path for the cooling fan #1 is through the engine cooling fan relay #3 and the right engine cooling fan motor. The result is a series circuit with both cooling fans running at low speed.
During high speed cooling fan operation the PCM supplies a ground path for the engine cooling fan relay #1. The PCM also supplies a ground path for engine cooling fan relay #2 and engine cooling fan relay #3. This closes all three cooling fan relays. During high speed fans operation, both the right and the left engine cooling fans are supplied current from the battery junction block and each cooling fan has its own ground path.
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 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. Refer to Powertrain Control Module Replacement/Programming
Step | Action | Value(s) | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to the Powertrain On Board Diagnostic (OBD) System Check Powertrain OBD System Check | |||||||||||||
Are any PCM DTC(s) stored? | -- | Diagnose the PCM DTC(s) first. Go to Powertrain Control Module Diagnosis 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 Air Conditioning (A/C) Compressor Clutch Control Diagnosis A/C Compressor Clutch Control 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 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 | Locate and repair short to battery positive voltage in circuit 532 and 504. If a problem is found repair as necessary. Refer to Repair Procedures in Electrical Diagnosis. Was a problem found? | -- | ||||||||||||||
16 |
Is the test light on ? | -- | ||||||||||||||
17 |
Is action complete? | -- | -- | |||||||||||||
18 | Probe Cool Fan 1 relay cavity 85 with a test light connected to ground. Is the test light on ? | -- | ||||||||||||||
19 |
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 Coolant Fan 1 relay control circuit between the PCM and Cool Fan 1 relay cavity 86. Is action complete? | -- | -- | |||||||||||||
27 |
Is the test light on ? | -- | ||||||||||||||
28 | Connect a test light between Fan 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 Air Conditioning (A/C) Compressor Clutch Control Diagnosis A/C Compressor Clutch Control Diagnosis | |||||||||||||
33 | Are both cooling fan(s) running at low speed? | -- | ||||||||||||||
34 | Remove Cool Fan 1 relay from the Underhood Electrical 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 battery positive voltage, probe Cool Fan 1 relay cavity 86. Is the test light on ? | -- | ||||||||||||||
37 | Replace Cool Fan 1 relay. Is action complete? | -- | -- | |||||||||||||
38 |
Is the test light on ? | -- | ||||||||||||||
39 | Locate and repair short to ground in the Cool 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? | 1.2V | ||||||||||||||
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 J 39200 Digital Multimeter connected to the A/C refrigerant pressure sensor ground. 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 circuit with a J 39200 J 39200 Digital Multimeter connected to the A/C refrigerant pressure sensor ground. 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 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 3 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 532. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||||||||
55 | Locate and repair short to battery positive voltage in CKT 504. Refer to Repair Procedures in Electrical Diagnosis. If a problem is found repair as necessary. Was a problem found? | -- | ||||||||||||||
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 battery positive voltage. 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 Cool Fan 2 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 Cool Fan 2 relay. Is action complete? | -- | -- | |||||||||||||
71 |
Is the test light on ? | -- | ||||||||||||||
72 | Locate and repair open in battery positive voltage circuit to Fan 3 relay cavity 85. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||||||||
73 | Probe Fan 3 relay cavity 87 in the Underhood Electrical Center with a test light to battery positive voltage. Is the test light on ? | -- | ||||||||||||||
74 | Locate and repair open in circuit between Fan 3 cavity 87and Fan 2 relay cavity 87a 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 3 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 PCM Replacement/Programming. Is action complete? | -- | -- | ||||||||||||||
78 | Repair open in the Cool Fan 2 relay cavity 86 and Cool relay cavity 86 control circuit to PCM. 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 |
