Cooling Fan Always On V6
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 the diagnostic category. |
Circuit/System Description
The engine control module (ECM) commands the fans ON in either high speed or low speed, depending on cooling requirements. In low speed, both fans are turned ON at a reduced speed. High speed has both fans turned ON at full speed.
In low speed operation, the ECM applies ground to the coil side of the low speed fan relay. This energizes the coil and applies voltage directly to the left cooling fan through the switch side of the low relay. The left fan is connected in series to the right cooling fan through the de-energized series/parallel (S/P) fan relay. The series circuit operates both fans at low speed.
In high speed operation, the ECM applies a ground to the coil side of the low speed fan relay, the S/P fan relay, and the high speed fan relay. When energized, the high speed fan relay applies voltage directly to the right cooling fan through the switch side of the relay. Simultaneously, the low speed fan relay and the S/P fan relay provide ignition voltage and a direct path to ground for the left cooling fan. With both fans connected in a parallel circuit, each fan receives full voltage and operates at high speed.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Cooling Fan Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Verify that DTCs P0480, P0481, P0691, P0692, P0693 and P0694 are not set.
- Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
- Ignition ON, observe that the fan is not activated.
| ⇒ | If any cooling system DTCs are set, repair the DTC first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle. |
Circuit/System Testing
- Ignition OFF, disconnect each cooling fan relay one at a time.
- Ignition ON, observe that the cooling fans are not activated.
Important: The following tests must be performed on each cooling fan relay.
| ⇒ | If the fans are activated, test for a short to voltage in the relay controlled output circuit. |
| ⇒ | If the fans are not activated, test or replace the cooling fan relay. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Cooling Fan Always On with RPO LC3 or LH2
Circuit/System Description
The engine control module (ECM) commands the fans ON in either high speed or low speed, depending on cooling requirements. In low speed, both fans are turned ON at a reduced speed. High speed has both fans turned ON at full speed.
In low speed operation, the ECM applies ground to the coil side of the low speed fan relay. This energizes the coil and applies voltage directly to the left cooling fan through the switch side of the low relay. The left fan is connected in series to the right cooling fan through the de-energized series/parallel (S/P) fan relay. The series circuit operates both fans at low speed.
In high speed operation, the ECM applies a ground to the coil side of the low speed fan relay, the S/P fan relay, and the high speed fan relay. When energized, the high speed fan relay applies voltage directly to the right cooling fan through the switch side of the relay. Simultaneously, the low speed fan relay and the S/P fan relay provide ignition voltage and a direct path to ground for the left cooling fan. With both fans connected in a parallel circuit, each fan receives full voltage and operates at high speed.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Cooling Fan Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Verify that DTCs P0480, P0481, P0691, P0692, P0693 and P0694 are not set.
- Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
- Ignition ON, observe that the fan is not activated.
| ⇒ | If any cooling system DTCs are set, repair the DTC first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle. |
Circuit/System Testing
- Ignition OFF, disconnect each cooling fan relay one at a time.
- Ignition ON, observe that the cooling fans are not activated.
Important: The following tests must be performed on each relay.
| ⇒ | If the fans are activated, test for a short to voltage in the relay controlled output circuit. |
| ⇒ | If the fans are not activated, test or replace the appropriate cooling fan relay. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
