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Cooling Fan Inoperative - LNP

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 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 scan tool cooling fan output control operates as follows:
       - Cooling Fan Relay 1 operates both fans at a low speed
       - Cooling Fan Relay 2 and 3 operates the left fan at a high speed
       - Cooling 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

Connector End View Reference

Component Connector End Views

Description and Operation

Cooling Fan Description and Operation : LNP or LNQ

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification
  1. Verify that DTC P0480 or P0481 is not set.
    2. ⇒If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
  2. Ignition ON, command the appropriate fan relay ON and OFF with a scan tool. Verify that the fans turn ON and OFF when changing between the commanded states.

Circuit/System Testing
  1. Ignition OFF, disconnect the KR20 cooling fan relays.
  2. Connect a 40 A fused jumper between the KR20E cooling fan speed control relay switch circuit terminal 30 and the ground circuit terminal 87. This completes the left hand side fan ground circuit. Leave this jumper in place for the remainder of this procedure.

    3. Note:  The following test must be performed on both the high speed fan relay circuit and the low speed fan relay circuit.

  3. Ignition ON, verify that a test lamp illuminates between ground and the relay switched ignition circuit terminal listed below:
    4. •  KR20J cooling fan left high speed relay terminal 87
    •  KR20K cooling fan right high speed relay terminal 87
    ⇒If the test lamp does not illuminate, test the appropriate relay switch B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the relay switch B+ circuit fuse is open, test the relay controlled output circuit for a short to ground. If the circuit tests normal, test or replace the appropriate G10 cooling fan motor.

    Note:  The following test must be performed first on the high speed fan relay circuit and next on the low speed fan relay circuit. Leave the jumper connected to the low speed fan relay circuit for the next test.

  4. Connect a 40 A fused jumper between the KR20 cooling fan relay circuit terminals listed below. Verify the appropriate fan is activated.
    5. •  KR20K cooling fan right high speed relay terminals 87 and 30
    •  KR20J cooling fan left high speed relay terminals 87 and 30
    ⇒If the corresponding cooling fan does not activate, test the relay controlled output circuit and the cooling fan ground circuit for an open/high resistance. If the circuits tests normal, replace the appropriate G10 cooling fan motor.
    ⇒ If the corresponding cooling fan activates, replace the appropriate KR20 cooling fan relay.
  5. Install the KR20E cooling fan speed control relay. Verify both fans activate at low speed.
    6. ⇒If both fans do not activate, test the relay controlled output circuit terminal 87A of the KR20E fan relay for a short to ground or an open/high resistance.
  6. If the circuits test normal, test or replace the KR20E cooling fan speed control relay.

Component Testing
  1. Ignition OFF, disconnect the KR20 cooling fan relay.
  2. Test for 70-110 Ω between terminals 85 and 86.
    3. ⇒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.
    4. • 30 and 86
    • 30 and 87
    • 30 and 85
    • 85 and 87
         ⇒If not the specified range, replace the KR20 cooling fan relay.
  4. Test the KR20E relay for less than 2 Ω between terminals 30 and 87A.
    5. ⇒If greater than the specified range, replace the KR20E cooling fan relay.
  5. Install a 20 A fused jumper wire between relay terminal 86 and B+. Install a jumper wire between relay terminal 85 and ground. Test for less than 2 Ω between terminals 30 and 87.
    6. ⇒If greater than the specified range, replace the KR20 cooling fan relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Relay Replacement : Within an Electrical Center → Attached to Wire Harness
    •  Engine Coolant Fan Replacement
   


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