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 Cooling 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.
During high speed cooling fan operation the PCM supplies a ground path for the low speed cooling fan relay through the cooling fan 1 control circuit. The PCM also 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. This closes all three fan relays. 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
Numbers below refer to the step numbers on the Diagnostic Table.
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Stored diagnostic trouble codes may affect engine cooling fan operation. 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 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.
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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 | Values | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||||||||||
Are any PCM DTCs stored? | -- | Go to Diagnostic Aids to diagnose DTCs first. Go to Powertrain Control Module Diagnosis | ||||||||||
3 |
Observe the cooling fans. Are the cooling fans running? | -- | ||||||||||
4 | Using scan tool output tests command Fan 1 ON. Do both cooling fans run at low speed? | -- | ||||||||||
5 | Using scan tool output tests command Fan 2 ON. Does the left side cooling fan run at high speed? | -- | ||||||||||
|
Important: Ambient temperature must be greater than 9°C (48°F).
Are the cooling fans running? | -- | Go to Diagnostic Aids | ||||||||||
7 | View the A/C Request display on the scan tool. Does the scan tool display Yes? | -- | Go to Powertrain Control Module Controlled Air Conditioning (A/C) Circuit Diagnosis | |||||||||
8 |
Is the test lamp ON? | -- | ||||||||||
9 | Probe low speed cooling fan relay switch feed with a test lamp to ground. Is the test lamp ON? | -- | ||||||||||
10 |
Are both cooling fans running at low speed? | -- | ||||||||||
11 |
Is the test lamp ON? | -- | ||||||||||
12 |
Was a problem found? | -- | ||||||||||
13 |
Was a problem found? | -- | ||||||||||
14 |
Is the test lamp ON at each cooling fan connection? | -- | ||||||||||
15 | Connect the test lamp between fan feed and ground terminals at both cooling fan connectors. Is the test lamp ON at each cooling fan feed terminal? | -- | ||||||||||
16 | Locate and repair open in fan feed circuit. Is action complete? | -- | -- | |||||||||
17 | Locate and repair open in the ground circuit to the affected cooling fan motors. Is action complete? | -- | -- | |||||||||
18 |
Is the test lamp ON? | -- | ||||||||||
19 | Probe high speed cooling fan relay cool circuit with a test lamp to ground. Is the test lamp ON? | -- | ||||||||||
20 |
Does the left side cooling fan run at high speed? | -- | ||||||||||
21 |
Is the test lamp ON? | -- | ||||||||||
22 |
Was a problem found? | -- | ||||||||||
23 |
Was a problem found? | -- | ||||||||||
24 |
Is the test lamp ON? | -- | ||||||||||
25 | Connect the test lamp between left side cooling fan motor harness connector high speed feed and motor ground terminals. Is the test lamp ON? | -- | ||||||||||
26 | Locate and repair open in the ground circuit to the left side cooling fan motor. Is action complete? | -- | -- | |||||||||
27 | Locate and repair open in high speed fan feed to the left side cooling fan. Is action complete? | -- | -- | |||||||||
28 | Locate and repair open in ignition feed (CKT 241) to the affected cooling fan relay. Is action complete? | -- | -- | |||||||||
29 | Locate and repair cause of no battery feed to the affected fan relay switch feed:
Is action complete? | -- | -- | |||||||||
30 | Disconnect the high speed cooling fan relay. Is either cooling fan running? | -- | ||||||||||
31 | Probe the high speed cooling fan relay harness connector control circuit terminal with a test lamp to B+. Is the test lamp ON? | -- | ||||||||||
32 | Observe A/C High Side Pressure on the scan tool. Is A/C High Side Pressure greater than the specified value? | 260 psi (1800 kPa) | Go to DTC P0530 Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit . | |||||||||
33 |
Is the test lamp ON? | -- | ||||||||||
34 | Locate and repair the short to ground in the high speed cooling fan relay control circuit. Is action complete? | -- | -- | |||||||||
35 | Disconnect the low speed cooling fan relay. Is either cooling fan ON? | -- | ||||||||||
36 | Probe the low speed cooling fan relay harness connector control circuit terminal with a test lamp to B+. Is the test lamp ON? | -- | ||||||||||
37 |
Is the test lamp ON? | -- | ||||||||||
38 | Locate and repair the short to ground in the low speed cooling fan relay control circuit. Refer to Wiring Repairs . Is action complete? | -- | -- | |||||||||
39 | Locate and repair short to B+ in affected cooling fan feed circuit. Is action complete? | -- | -- | |||||||||
40 |
Was a problem found? | -- | ||||||||||
41 | Replace the low speed cooling fan relay. Is action complete? | -- | -- | |||||||||
42 |
Was a problem found? | -- | ||||||||||
43 | Replace the high speed cooling fan relay. Is action complete? | -- | -- | |||||||||
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Important: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is action complete? | -- | -- | ||||||||||
45 | Replace the affected cooling fan motor. Is action complete? | -- | -- | |||||||||
46 |
Are the cooling fans running? | -- | ||||||||||
47 | Using scan tool output tests command Fan 1 ON. Do both cooling fans run at low speed? | -- | ||||||||||
48 | Using scan tool output tests command Fan 2 ON. Does the left side cooling fan run at high speed? | -- | System OK |
