Cooling Fan Always On (Single Fan)
Cooling Fan Always On (Single Fan)
Circuit/System Description
The engine cooling fan system consists of one electrical cooling fan, a serviceable resistor module mounted in the cooling fan shroud, and three fan relays. The relays are arranged in a series parallel (S/P) configuration that allows the engine control module (ECM) to operate the fan at low, medium, or high speeds, depending on cooling requirements. The resistor module is a self-contained unit providing a specific resistance through three individual circuits. To activate the fan, the ECM applies ground to the coil side of the applicable fan relays. The cooling fan and fan relays receive battery voltage from the underhood fuse block. The ground path for the operation of the cooling fan is provided at G104.
Diagnostic Aids
* The scan tool cooling fan output control operates as follows:
- Cooling Fan Relay 1 operates the fan at a low speed
- Cooling Fan Relay 2 and 3 operates the fan at a medium speed
- Cooling Fan Relay 1, 2 and 3 operates the fan at a high speed
* KR20 cooling fan relay identification:
- KR20C cooling fan low speed FAN 1 Relay
- KR20D cooling fan high speed FAN 2 Relay
- KR20E cooling fan speed control FAN 3 or S/P Relay
* 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 (Connector End Views By Name)
Description and Operation
Cooling Fan Description and Operation (Cooling Fan)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON, observe the DTC information with a scan tool. Verify that DTC P0480, P0481, P0691, P0692, P0693, P0694 is not set.
• If a DTC is set, refer to DTC P0480 or P0481 (V8 and V6-LF1, LGD - Dual Fan) (Engine Cooling)DTC P0480 or P0481 (V6-LF1) (V6-LF1) for V8 or V6 LF1, or DTC P0480, P0481, P0691, P0692, P0693, or P0694 (w/LLT) ()DTC P0480, P0481, P0691, P0692, P0693, or P0694 (w/LLT and Dual Fan) () for V6 LLT.
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 fan is not activated.
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 the cooling fan is not activated.
• If the fan is activated, test for a short to voltage in the relay controlled output circuits.
• If the fans is not activated, test or replace the appropriate cooling fan relay.
Component Testing
1. Ignition OFF, disconnect the appropriate cooling fan relay.
2. Test for 200-240 ohm between terminals 85 and 86 of the relay.
• If not within the specified range, replace the 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 not the specified value, replace the relay.
4. Test for less than 2 ohm between terminals 30 and 87A.
• If greater than the specified range, replace the relay.
5. Install a 20 A fused jumper wire between B+ and relay terminal 85. Connect a jumper wire between relay terminal 86 and ground. Test for less than 2 ohm between terminals 30 and 87.
• If greater than the specified range, replace the cooling fan relay.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))