For 1990-2009 cars
Engine Controls Components
Cell 20: Cooling Fans
OBD II Symbol Description Notice

### 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.

1. 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.

2. 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.

3. 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.

#### Electric Cooling Fan Diagnosis

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Are any PCM DTCs stored? | -- | Go to Diagnostic Aids to diagnose DTCs first. Go to Powertrain Control Module Diagnosis | Go to Step 3
3 |

1. Engine coolant temperature less than 100°C (212°F).
2. Ensure that the A/C is OFF.
3. Engine running.

Observe the cooling fans.

Are the cooling fans running?

--

Go to Step 30

Go to Step 4

4 | Using scan tool output tests command Fan 1 ON. Do both cooling fans run at low speed? | -- | Go to Step 5 | Go to Step 8
5 | Using scan tool output tests command Fan 2 ON. Does the left side cooling fan run at high speed? | -- | Go to Step 6 | Go to Step 18
6 | Important: Ambient temperature must be greater than 9°C (48°F).

1. Exit scan tool output tests.
2. Engine running.
3. Turn the A/C ON.

Are the cooling fans running?

--

Go to Diagnostic Aids

Go to Step 7

7 | View the A/C Request display on the scan tool. Does the scan tool display Yes? | -- | Go to Step 44 | Go to Powertrain Control Module Controlled Air Conditioning (A/C) Circuit Diagnosis
8 |

1. Turn OFF the ignition switch.
2. Disconnect the low speed cooling fan relay.
3. Turn ON the ignition switch.
4. Probe low speed cooling fan relay cool feed with a test lamp connected to ground

Is the test lamp ON?

--

Go to Step 9

Go to Step 28

9 | Probe low speed cooling fan relay switch feed with a test lamp to ground. Is the test lamp ON? | -- | Go to Step 10 | Go to Step 29
10 |

1. Connect a fused jumper between low speed cooling fan relay switch feed and fan feed at relay connector.
2. Observe the cooling fans.

Are both cooling fans running at low speed?

--

Go to Step 11

Go to Step 14

11 |

1. Using the scan tool output control function, select Fan 1 and command the cooling fans ON.
2. Probe low speed cooling fan control circuit at harness connector with a test lamp to B+.

Is the test lamp ON?

--

Go to Step 40

Go to Step 12

12 |

1. Turn OFF the ignition switch.
2. Disconnect the PCM.
3. Turn ON the ignition switch.
4. Check the low speed cooling fan relay control circuit for an open or short to voltage between the PCM and the low speed cooling fan relay.
5. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 46

Go to Step 13

13 |

1. Check the low speed cooling fan relay control circuit for a poor terminal connection at the PCM.
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 46

Go to Step 44

14 |

1. Disconnect both cooling fan motor harness connectors (leave low speed cooling fan relay connector terminals jumpered).
2. Probe fan feed at both cooling fan motor connectors with a test lamp to ground.

Is the test lamp ON at each cooling fan connection?

--

Go to Step 15

Go to Step 16

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? | -- | Go to Step 45 | Go to Step 17
16 | Locate and repair open in fan feed circuit. Is action complete? | -- | Go to Step 46 | --
17 | Locate and repair open in the ground circuit to the affected cooling fan motors. Is action complete? | -- | Go to Step 46 | --
18 |

1. Disconnect the high speed cooling fan relay.
2. Turn ON the ignition switch.
3. Probe high speed cooling fan relay switch feed with a test lamp to ground.

Is the test lamp ON?

--

Go to Step 19

Go to Step 29

19 | Probe high speed cooling fan relay cool circuit with a test lamp to ground. Is the test lamp ON? | -- | Go to Step 20 | Go to Step 28
20 |

1. Connect a fused jumper between high speed cooling fan relay switch feed and motor feed terminals at harness connector.
2. Observe the left side cooling fan.

Does the left side cooling fan run at high speed?

--

Go to Step 21

Go to Step 24

21 |

1. Using the scan tool output control function, select Fan 2 and command the fan ON.
2. Wait 6 seconds.
3. Probe high speed cooling fan relay control circuit at harness connector terminal with a test lamp to B+.

Is the test lamp ON?

--

Go to Step 42

Go to Step 22

22 |

1. Turn OFF the ignition switch.
2. Disconnect the PCM.
3. Turn ON the ignition switch.
4. Check the high speed cooling fan relay control circuit for an open or short to voltage between the PCM and the high speed cooling fan relay.
5. If a problem is found, repair as necessary. Refer to Wiring Repairs .

Was a problem found?

--

Go to Step 46

Go to Step 23

23 |

1. Check the high speed cooling fan relay control circuit for a poor terminal connection at the PCM.
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 46

Go to Step 44

24 |

1. Disconnect the left side cooling fan motor connector (leave high speed cooling fan relay harness connector terminals jumpered).
2. Probe the left side cooling fan motor harness fan feed connector B with a test lamp to ground.

Is the test lamp ON?

--

Go to Step 25

Go to Step 27

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? | -- | Go to Step 45 | Go to Step 26
26 | Locate and repair open in the ground circuit to the left side cooling fan motor. Is action complete? | -- | Go to Step 46 | --
27 | Locate and repair open in high speed fan feed to the left side cooling fan. Is action complete? | -- | Go to Step 46 | --
28 | Locate and repair open in ignition feed (CKT 241) to the affected cooling fan relay. Is action complete? | -- | Go to Step 46 | --
29 | Locate and repair cause of no battery feed to the affected fan relay switch feed:

• | Open or short to ground in CKT 742. Refer to Wiring Repairs .

• | Shorted cooling fan motor windings.

• | Right motor feed shorted to ground. Refer to Wiring Repairs .

• | Left motor high speed feed shorted to ground. Refer to Wiring Repairs .

Is action complete?

--

Go to Step 46

--

30 | Disconnect the high speed cooling fan relay. Is either cooling fan running? | -- | Go to Step 35 | Go to Step 31
31 | Probe the high speed cooling fan relay harness connector control circuit terminal with a test lamp to B+. Is the test lamp ON? | -- | Go to Step 32 | Go to Step 43
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 . | Go to Step 33
33 |

1. Turn OFF the ignition switch.
2. Disconnect the PCM.
3. Turn ON the ignition switch.
4. Probe the high speed cooling fan relay harness connector control circuit terminal with a test lamp to B+.

Is the test lamp ON?

--

Go to Step 34

Go to Step 44

34 | Locate and repair the short to ground in the high speed cooling fan relay control circuit. Is action complete? | -- | Go to Step 46 | --
35 | Disconnect the low speed cooling fan relay. Is either cooling fan ON? | -- | Go to Step 39 | Go to Step 36
36 | Probe the low speed cooling fan relay harness connector control circuit terminal with a test lamp to B+. Is the test lamp ON? | -- | Go to Step 37 | Go to Step 41
37 |

1. Turn OFF the ignition switch.
2. Disconnect the PCM.
3. Turn ON the ignition switch.
4. Probe the low speed cooling fan relay harness connector control circuit terminal with a test lamp to B+.

Is the test lamp ON?

--

Go to Step 38

Go to Step 44

38 | Locate and repair the short to ground in the low speed cooling fan relay control circuit. Refer to Wiring Repairs . Is action complete? | -- | Go to Step 46 | --
39 | Locate and repair short to B+ in affected cooling fan feed circuit. Is action complete? | -- | Go to Step 46 | --
40 |

1. Check for poor connections at the low speed cooling fan relay. Refer to Wiring Repairs
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 46

Go to Step 41

41 | Replace the low speed cooling fan relay. Is action complete? | -- | Go to Step 46 | --
42 |

1. Check for poor connections at the high speed cooling fan relay.
2. If a problem is found, repair as necessary.

Was a problem found?

--

Go to Step 46

Go to Step 43

43 | Replace the high speed cooling fan relay. Is action complete? | -- | Go to Step 46 | --
44 | Important: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is action complete? | -- | Go to Step 46 | --
45 | Replace the affected cooling fan motor. Is action complete? | -- | Go to Step 46 | --
46 |

1. Engine coolant temperature is less than 100°C (212°F).
2. Ensure that the A/C is OFF.
3. Engine running.

Are the cooling fans running?

--

Go to Step 30

Go to Step 47

47 | Using scan tool output tests command Fan 1 ON. Do both cooling fans run at low speed? | -- | Go to Step 48 | Go to Step 8
48 | Using scan tool output tests command Fan 2 ON. Does the left side cooling fan run at high speed? | -- | System OK | Go to Step 18