Cooling Fan Always On
Cooling Fan Always On
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Circuit/System Description
The engine cooling fan system consists of a cooling fan assembly containing two electric cooling fans. The engine control module (ECM) uses two fan control circuits and a series of three relays to command 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.
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 scan tool cooling fan control function operates as follows:
- Fan Relay 1 operates both fans at a low speed
- Fan Relay 2 and 3 operates the right fan at a high speed
- Fan Relay 1, 2 and 3 operates both fans at a high speed
* When disconnecting or removing fuses and relays from a fuse block, always inspect the component electrical terminals for corrosion and the correct orientation in the fuse block. Test the mating electrical terminals for tightness.
Reference Information
Schematic Reference
Engine Cooling Schematics [1][2]Cooling System
Connector End View Reference
* Component Connector End Views A/C Compressor Clutch
* Electrical Center Identification Views Fuse Block - Underhood Label
Description and Operation
Cooling Fan Description and Operation Cooling Fan
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON, observe the DTC information with a scan tool. Verify DTC P0480, P0481, P0691, P0692, P0693, or P0694 is not set.
• If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.
2. Ignition ON, observe the scan tool FC Relay 1 and FC Relay 2 and 3 Command parameters. The parameters should display OFF.
3. Ignition ON, observe that the engine cooling fans are not ON.
Circuit/System Testing
Note:
The following tests must be performed on each cooling fan relay.
1. Ignition OFF, disconnect each KR20 cooling fan relay one at a time.
2. Ignition ON, observe that both fans are now OFF.
• If the fans are ON, test for a short to voltage in the relay controlled output circuit of the appropriate cooling fan.
• If the fans are OFF, test or replace the appropriate KR20 cooling fan relay.
Component Testing
1. Ignition OFF, disconnect the KR20 cooling fan relay.
2. Test for 70-110 ohms between terminals 85 and 86.
• If not within the specified range, replace the KR20 cooling fan relay.
3. Measure the resistance between the terminals listed below. The DMM should display OL.
* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87
• If less than the specified range, replace the KR20 cooling fan relay.
4. Test the Fan 2 relay for less than 2 ohms between terminals 30 and 87A.
• If greater than the specified range, replace the Fan 2 relay.
5. Connect a 20 A fused jumper wire between relay terminal 85 and B+. Connect a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87.
• If greater than the specified range, replace the KR20 cooling fan relay.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Accessory Wiring Junction Block Replacement Accessory Wiring Junction Block Replacement
* Relay Replacement (Within an Electrical Center) Relay Replacement (Within an Electrical Center)Relay Replacement (Attached to Wire Harness) Relay Replacement (Attached to Wire Harness)