For 1990-2009 cars

### Circuit Description:

The cooling fans are controlled by the PCM based on various inputs. Battery voltage is supplied to the primary and secondary cooling fan relays (switch side). Ignition voltage is supplied to the primary and secondary cooling fan relays (coil side). The PCM controls the cooling fan relays by providing a ground path.

The PCM will enable the engine cooling fans when certain Diagnostic Trouble Codes are set. For the Fan schematic, refer to

#### Engine Cooling Fan Control - w/o VO8

Engine Controls Components
Powertrain Control Module (PCM)
Engine Cooling Fan Control - VO8
A/C Controls - C67 and C68
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
or

#### Engine Cooling Fan Control - VO8

Engine Controls Components
Powertrain Control Module (PCM)
Engine Cooling Fan Control - w/o VO8
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
.

### Diagnostic Aids

If the owner complained of an overheating problem, it must be determined if the complaint was due to an actual boil over, or the warning indicator light, or engine coolant temperature gage indicated overheating. The gage accuracy can also be checked by comparing the Engine Coolant Temperature (ECT) sensor reading using a scan tool and comparing its reading with the gage reading. If the engine is actually overheating and the gage indicated overheating, but the cooling fan is not coming ON, the Engine Coolant Temperature (ECT) sensor has probably shifted out of calibration and should be replaced.

If the engine is overheating and the cooling fans are ON, the cooling system should be checked, refer to Section 6B.

The PCM will command fan 1 ON at 107°C (225°F) and OFF at 103°C (218°F) and, fan 2 ON at 111°C (232°F) and OFF at 107°C (225°F).

### Test Description

Number(s) below refer to number(s) on the diagnostic table.

1. The PCM will enable the engine cooling fans when certain Diagnostic Trouble Codes are set. Go to applicable DTC Table first before proceeding with this table.

2. Allow engine coolant temperature to cool below 100°C (212°F) before proceeding with diagnosis diagnoses.

#### Electric Cooling Fan Functional Check

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Powertrain OBD System Check
2 | Are any DTCs set? | -- | Go to applicable DTC Table | Go to Step 3
3 |

1. Install the scan tool.
2. The engine coolant temperature must be below the specified value for all the fan diagnoses.
3. Turn the ignition ON, Engine OFF and A/C OFF.

Are the cooling fans OFF?

100°C (212°F)

Go to Step 4

Go to Step 6

4 | Using a scan tool, command the cooling fan relay(s) ON. Are both cooling fans ON? | -- | Go to Step 5 | Go to Step 9
5 | With the engine idling, turn the A/C ON. Are the cooling fan(s) ON? | -- | System OK | Go to A/C request circuit diagnosis
6 | Disconnect the cooling fan relay for the cooling fan that is operating. Does the cooling fan stop? | -- | Go to Step 7 | Go to Step 8
7 | Replace the cooling fan relay. Is the action complete? | -- | System OK | --
8 | Repair the circuit between the fan relay and the fan motor for a short to voltage. Is the action complete? | -- | System OK | --
9 |

1. Turn the ignition OFF.
2. Disconnect the cooling fan relay for the cooling fan that is not operating.
3. Turn the ignition ON.
4. Using a test light connected to ground, probe the battery feed side of the cooling fan relay electrical harness, contact side.

Does the test light illuminate?

--

Go to Step 10

Go to Step 16

10 | Using a fused jumper wire, jumper the cooling fan relay electrical harness from the battery feed circuit to the circuit going to the fan motor (leave jumper installed for the remainder of the steps). Does the cooling fan operate? | -- | Go to Step 17 | Go to Step 11
11 |

1. Turn the ignition OFF.
2. Disconnect the cooling fan electrical connector for the fan that did not operate.
3. Turn the ignition ON.
4. Connect a test light across the cooling fan electrical connector terminals.

Does the test light illuminate?

--

Go to Step 18

Go to Step 12

12 | Probe the cooling fan motor harness connector power feed circuit with a test light connected to ground. Does the test light illuminate? | -- | Go to Step 13 | Go to Step 15
13 | Check the connection at the fan motor harness connector. If a faulty connection is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis (8A Cell 5). Was a problem found and corrected? | -- | System OK | Go to Step 14
14 | Repair open fan motor ground circuit. Refer to Repair Procedures in Electrical Diagnosis (8A Cell 5). Is the action complete? | -- | System OK | --
15 | Repair open power feed circuit between the fan relay and the cooling fan motor. Refer to Repair Procedures in Electrical Diagnosis (8A Cell 5). Is the action complete? | -- | System OK | --
16 | Repair open battery feed circuit to the fan relay. Refer to Repair Procedures in Electrical Diagnosis (8A Cell 5). Is the action complete? | -- | System OK | --
17 | Replace the cooling fan relay. Is the action complete? | -- | System OK | --
18 | Replace the cooling fan motor. Is the action complete? | -- | System OK | --