Cooling Fan Always On (LBN, LEA, LE9, LLU, or LTD)
Cooling Fan Always On (LBN, LEA, LE9, LLU, or LTD)
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 the diagnostic category.
Circuit/System Description
The engine cooling fan system is composed of one cooling fan, a series of 5 relays, the engine control module (ECM), and the associated wiring. The cooling fan assembly includes two resistors. This combination of components enables the ECM to operate the cooling fan at 3 speeds using two fan control circuits.
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
* 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.
* If the cooling fan operates at high speed when the ECM is requesting medium speed operation, test or replace the KR20E cooling fan speed control relay.
Reference Information
Schematic Reference
* Engine Cooling Schematics [1][2]Cooling System
* Electrical Center Identification Views X70A Relay Block - Underhood Top View
Connector End View Reference
* Component Connector End Views Sunshade - Left (DH6)
* Electrical Center Identification Views X70A Relay Block - Underhood Top View
Description and Operation
Cooling Fan Description and Operation (LFW) Cooling Fan Description and Operation (LFW)Cooling Fan Description and Operation (LBN, LEA, LE9, LLU, or LTD) Cooling Fan Description and Operation (LBN, LEA, LE9, LLU, or LTD)
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 Control Module References 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, or P0694 is not set.
• If any cooling system DTCs are set, repair the DTC first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.
2. Ignition ON, observe the scan tool Cooling Fan Relay 1 and Cooling Fan Relays 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 in the order listed below.
* KR20F cooling fan relay
* KR20C cooling fan low speed relay
* KR20P cooling fan medium speed relay
* KR20D cooling fan high speed relay
2. Ignition ON, observe that the fan is not activated after each relay is removed.
• If the fan is not activated, replace the appropriate KR20 relay.
3. If the fan is activated after all the relays are removed, test the relay controlled output circuit of the relays listed below for a short to voltage.
* KR20C cooling fan low speed relay
* KR20P cooling fan medium speed relay
* KR20D cooling fan high speed relay
Component Testing
1. Ignition OFF, disconnect the KR20 cooling fan relay.
2. Test for 70-110 ohms between terminals 85/2 and 86/1, 95-135 ohms for the KR20F relay.
• 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.
* 30/3 and 86/1
* 30/3 and 87/5
* 30/3 and 85/2
* 85/2 and 87/5
• If less than the specified range, replace the KR20 cooling fan relay.
4. Connect a 20 A fused jumper wire between relay terminal 85/2 and B+. Connect a jumper wire between relay terminal 86/1 and ground. Test for less than 2 ohms between terminals 30/3 and 87/5.
• 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.
Relay Replacement (Within an Electrical Center) Relay Replacement (Within an Electrical Center)Relay Replacement (Attached to Wire Harness) Relay Replacement (Attached to Wire Harness)