| Table 1: | Cooling FAN 1 Relay |
| Table 2: | Cooling FAN 2 Relay |
| Table 3: | Cooling FAN 3 Relay |
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 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 1 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 fan 2 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 1 relay, the series/parallel fan 2 relay, and the high speed fan 3 relay. When energized, the high speed fan 3 relay applies voltage directly to the right cooling fan through the switch side of the relay. Simultaneously, the low speed fan 1 relay and the series/parallel fan 2 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.
Diagnostic Aids
| • | The ECM has the capability of providing command to the fan relays even when a scan tool output control is being used. Always refer to the fan control command parameters on the scan tool to know which fans are being commanded ON by the ECM. |
| • | The following tables illustrate the FAN 1 relay, FAN 2 relay and the FAN 3 relay terminal locations in the underhood fuse block: |
Terminal Identification | |
|---|---|
Relay Switch B+ | Relay Coil Control |
Relay Coil B+ | Relay Controlled Output |
Front of Vehicle | |
Terminal Identification | |
|---|---|
Relay Switch B+ | Relay Coil Control |
-- | Relay Controlled Output |
Relay Coil B+ | Ground |
Front of Vehicle | |
Terminal Identification | |
|---|---|
Relay Coil Control | Relay Controlled Output |
Relay Switch B+ | Relay Coil B+ |
Front of Vehicle | |
Reference Information
Schematic Reference
Description and Operation
Cooling System Description and Operation
Connector End View Reference
Cooling System Connector End Views
Electrical Information Reference
Scan Tool Reference
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 control module is not commanding fan activation.
- Observe that the fans are not activated.
| ⇒ | If any cooling system DTCs are set, repair the DTC first. Refer to DTC P0480, P0481, P0691, P0692, P0693, or P0694 . |
Circuit/System Testing
- Ignition OFF, disconnect each cooling fan relay one at a time.
- Ignition ON, observe that the cooling fans are not activated.
| ⇒ | If the fans are activated, test for a short to voltage in the relay controlled output circuits. |
| ⇒ | If the fans are not activated, test or replace the appropriate cooling fan relay. |
Component Testing
- Ignition OFF, disconnect the cooling fan relay.
- Test for 70-110 ohms of resistance between terminals 85 and 86.
- Test for infinite resistance between the following terminals:
- Test for less than 2 ohms of resistance between terminals 30 and 87A.
- Install a 20A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms of resistance between terminals 30 and 87.
| ⇒ | If the resistance is not within the specified range, replace the relay. |
| • | 30 and 86 |
| • | 30 and 87 |
| • | 30 and 85 |
| • | 85 and 87 |
| ⇒ | If not the specified range, replace the relay. |
| ⇒ | If greater than the specified range, replace the relay. |
| ⇒ | If greater than the specified range, replace the relay. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
