Cooling Fan Always On Except LAT
Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit/System Description
The engine control module (ECM) commands the fans ON in high speed or low speed. In low speed, the fans are configured in series. In high speed, the fans are configured in parallel.
In low speed operation, the ECM applies ground to the coil side of the low speed relay, which is the auxiliary fan relay 12. Voltage is applied directly to the left cooling fan through the switch side of the low speed relay. The right fan is connected in series to the left fan through the de-energized series/parallel relay, which is fan control relay 15, so that both fans operate at low speed.
In high speed operation, the ECM applies a ground to the coil side of the low speed fan relay, the series/parallel relay, and the high speed fan relay, which is the main fan relay 16. Voltage is applied directly to the right cooling fan through the switch side of the high speed fan relay. The left cooling fan obtains voltage through the low speed fan relay and ground through the series/parallel relay.
When the ECM is commanding a fan relay ON, the voltage of the control circuit should be low, near 0 volts. When the ECM is commanding a fan relay OFF, the voltage of the control circuit should be high, near battery voltage.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Cooling Fan Description and Operation
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Verify that the following DTCs are not set: P0480, P0481.
- Verify with a scan tool that the ECM is not commanding fan relay activation.
- Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
- Ignition ON, observe that the fans are not activated.
| ⇒ | If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle . |
Circuit/System Testing
Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
- Ignition OFF, leave the series/parallel relay, which is fan control relay 15, in place while disconnecting the other relays.
- Ignition ON, observe that the fans are not activated.
| ⇒ | If the fans are not activated, replace the faulty relay. |
| ⇒ | If a fan is activated, test the fan voltage supply circuits for a short to voltage. |
Repair Instructions
| • | Control Module References for ECM replacement, setup, and programming |
Repair Verification
- Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
- Ignition ON, observe that the fan is not activated.
Cooling Fan Always On LAT
Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit/System Description
The engine control module (ECM) grounds the low speed relay, which is the AUX fan relay, and the high speed relay, which is the main fan relay, control circuits through an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line that is monitored by the ECM. When the ECM is commanding a component ON, the voltage potential of the control circuit should be low, near 0 volts. When the ECM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be high, near battery voltage.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Cooling Fan Description and Operation
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- If DTCs P0480 or P0481 are set, then perform those diagnostics first.
- Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
- Ignition ON, observe that the fan is not activated.
Circuit/System Testing
Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
- Ignition OFF, disconnect the relays.
- Ignition ON, observe that the fan is not activated.
| ⇒ | If the fan is not activated, replace the faulty relay. |
| ⇒ | If the fan is activated, test the fan voltage supply circuits for a short to voltage. |
Repair Instructions
| • | Engine Control Module Replacement for the 2.4L engine |
Repair Verification
- Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
- Ignition ON, observe that the fan is not activated.
Cooling Fan Always On LAT
Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit/System Description
The engine control module (ECM) grounds the fan main relay and the fan main relay control circuits through an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line that is monitored by the ECM. When the ECM is commanding a component ON, the voltage potential of the control circuit should be low, near 0 volts. When the ECM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be high, near battery voltage. If the ECM detects that the actual state of the control circuit does not match the expected state, a DTC will set.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Cooling Fan Description and Operation
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- If DTCs P0480 or P0481 are set, perform those diagnostics first.
- Ignition ON, verify with a scan tool that the control module is not commanding fan activation.
- Ignition ON, observe that the fan is not activated.
Circuit/System Testing
- Ignition ON, disconnect the fan AUX relay. Observe that the fan is ON.
- Disconnect the fan main relay. Observe that the fan is ON.
- Test the relay control circuit terminal 87 for a short to voltage:
| ⇒ | If OFF, replace the relay. |
| ⇒ | If OFF, replace the relay. |
Repair Instructions
Cooling Fan and Shroud Replacement
Repair Verification
Ignition ON, command the relay ON and OFF with a scan tool. Observe to verify that the fan turns ON and OFF with each command.
Cooling Fan Always On LE5
Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit/System Description
The engine control module (ECM) commands the fans ON in high speed or low speed. In low speed, the fans are configured in series. In high speed, the fans are configured in parallel.
In low speed operation, the ECM applies ground to the coil side of fan relay. Voltage is applied directly to the left cooling fan through the switch side of fan AUX relay 3. The right fan is connected in series to the left fan through the de-energized FAN CTRL relay so that both fans operate at low speed.
In high speed operation, the ECM applies a ground to the coil side of fan AUX relay, FAN CTRL relay, and fan main relay. Voltage is applied directly to the right cooling fan through the switch side of fan main relay. The left cooling fan obtains voltage through fan AUX relay and ground through FAN CTRL relay 2.
When the ECM is commanding a fan relay ON, the voltage of the control circuit should be low, near 0 volts. When the ECM is commanding a fan relay OFF, the voltage of the control circuit should be high, near battery voltage.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Cooling Fan Description and Operation
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- If DTC P0480 or P0481 are set, perform those diagnostics first.
- Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
- Ignition ON, observe that the fans are not activated.
Circuit/System Testing
- Ignition OFF, disconnect FAN AUX relay.
- Ignition ON, observe that both fans are now OFF.
| ⇒ | If both fans are OFF, replace FAN AUX relay. If either fan is still activated, remove fan main relay. If both fans are now OFF, replace fan main relay. If either fan is still activated, test for a short to voltage in the fan voltage supply circuit. |
Repair Instructions
Cooling Fan and Shroud Replacement
Repair Verification
Ignition ON, command the relay ON and OFF with a scan tool. Observe to verify that the fan turns ON and OFF with each command.
