Refer to
Cooling Fans
.
Circuit Description:
Power for the fan motors is supplied through the Cooling Fan fuse in the RH Maxi fuse block. The cooling fan relays are energized when current flows from the Clng Fan fuse in the IP fuse block through the relay coils to ground through the PCM. The cooling fan 1 control circuit is grounded for low speed fan operation. The cooling fan 1 and cooling fan 2 control circuits are grounded for high speed operation.
During low speed fan operation the PCM supplies a ground path for the low speed cooling fan relay #1. This closes the low speed relay contacts, allowing current to flow from the battery junction block through the relay contacts to the primary cooling fan. During low speed operation, the ground path for the primary cooling fan is through the series/parallel cooling fan relay and secondary cooling fan motor. The result is a series circuit with both fans running at low speed.
To command high speed cooling fan operation the PCM first supplies a ground path for the low speed cooling fan relay through the cooling fan 1 control circuit. After a 6 second delay, the PCM supplies a ground path for the high speed cooling fan relay #3 and the series/parallel cooling fan relay #2 through the cooling fan 2 control circuit. All 3 cooling fan relays are closed for high speed cooling fans operation. During high speed operation, both the primary and the secondary cooling fans are supplied current from the battery junction block and each 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 greater than 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 powertrain DTC(s) stored? | -- | Diagnose the DTC(s) first. Go 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 greater than 9°C (48°F).
Are the cooling fans running? | -- | Refer 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 primary cooling fan running? | -- | ||||||||||||||
10 |
Is the primary cooling fan running? | -- | ||||||||||||||
11 | Remove the series/parallel cooling fan #2 relay from the RH Underhood Relay Center. Is the primary cooling fan running? | -- | ||||||||||||||
12 | Locate and repair short to ground in CKT 504. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||||||||
13 |
Was a problem found? | -- | ||||||||||||||
14 |
Is the secondary cooling fan running? | -- | ||||||||||||||
15 | Replace the primary cooling fan diode. Refer to Cooling Fans in Electrical Diagnosis. Is action complete? | -- | -- | |||||||||||||
16 |
Is the test light ON? | -- | ||||||||||||||
17 |
Is action complete? | -- | -- | |||||||||||||
18 | Probe low speed cooling fan relay harness connector 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 | Repair open in the cooling fan 1 control CKT 335 between the PCM and the low speed cooling fan relay. Is action complete? | -- | -- | |||||||||||||
27 |
Is the test light ON? | -- | ||||||||||||||
28 | Connect a test light between RH Front Underhood Relay Center series/parallel cooling fan #2 relay 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 | Disconnect the low speed cooling fan relay. Are the cooling fans running? | -- | ||||||||||||||
35 | Locate and repair short to voltage in CKT 532. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||||||||
36 | Using a test light connected to B+, probe low speed cooling fan relay harness connector cavity 86. Is the test light ON? | -- | ||||||||||||||
37 | Replace the low speed cooling fan relay. Is action complete? | -- | -- | |||||||||||||
38 |
Is the test light ON? | -- | ||||||||||||||
39 | Locate and repair short to ground in the cooling fan 1 control circuit (CKT 335). 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 secondary 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 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 B+. Is the test light ON? | -- | ||||||||||||||
47 | Probe the A/C refrigerant pressure sensor 5 volt reference circuit B with a 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 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 secondary cooling fan running at high speed? | -- | ||||||||||||||
53 | Remove series/parallel cooling fan #2 relay from the RH Front Underhood Relay Center. Is the secondary cooling fan running at high speed? | -- | ||||||||||||||
54 | Locate and repair short to B+ in CKT 409. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||||||||
55 | Locate and repair short to B+ in CKT 504. 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 (CKT 504) at the primary 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 positive voltage circuit to high speed cooling fan #3 relay. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||||||||
66 | Probe high speed cooling fan #3 relay cavity 87 in the RH Front Underhood Relay Center with a test light connected to ground. Is the test light ON? | -- | ||||||||||||||
67 | Locate and repair open in battery positive voltage circuit to high speed cooling fan #3 relay cavity 87. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||||||||
68 |
Was a problem found? | -- | ||||||||||||||
69 |
Was a problem found? | -- | ||||||||||||||
70 | Replace high speed cooling fan #3 relay. Is action complete? | -- | -- | |||||||||||||
71 |
Is the test light ON? | -- | ||||||||||||||
72 | Locate and repair open in battery positive voltage circuit to series/parallel cooling fan #2 relay cavity 85 in the RH Front Underhood Relay Center. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||||||||
73 | Probe series/parallel cooling fan #2 relay cavity 87 in the RH Front Underhood Relay Center with a test light to B+. Is the test light ON? | -- | ||||||||||||||
74 | Locate and repair open in CKT 1350 between series/parallel cooling fan #2 relay cavity 87 in the RH Front Underhood Relay Center cavity and ground. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||||||||
75 |
Was a problem found? | -- | ||||||||||||||
76 | Replace the series/parallel cooling fan #2 relay. 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 cooling fan 2 control circuit (CKT 473) between the series/parallel cooling fan #2 relay cavity 86 and the high speed cooling fan #3 relay cavity 86. Refer to Repair Procedures in Electrical Diagnosis. Is action complete? | -- | -- | |||||||||||||
79 | Replace the primary cooling fan motor. Refer to On-Vehicle Service in Cooling and Radiator. Is action complete? | -- | -- | |||||||||||||
80 | Replace the secondary 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 |
