Cooling Fan Malfunction (LE5)
Diagnostic Fault Information
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
Circuit/System Description
The engine control module (ECM) commands the fan on in either high speed or low
speed, depending on cooling requirements. In low speed, the fan is turned on at a reduced
speed. High speed has the fan turned on at a higher speed.
In low speed operation, the ECM applies ground to the coil side of the COOL/FAN Relay
1. This energizes the coil and applies voltage to the low speed windings of the fan
through the switch side of the COOL/FAN Relay 1, which is fed by the COOL/FAN 1
fuse 30A. In low speed, the COOL /FAN 1Relay passes voltage to the Cooling Fan
Motor Low Speed Winding. From the Cooling Fan Motor, a ground path is given through
G111.
In high speed operation, the ECM applies a ground to the coil side of the COOL/FAN 2
Relay, and COOL/FAN 1 Relay. On the COOL/FAN 2 Relay, the energized coil closes
the switch side of the relay and applies voltage to the Cooling Fan Motor High Speed
Winding. From the Cooling Fan Motor, a ground path is given through S110 and then
G111.
Reference Information
Schematic Reference
Engine Heating/Cooling Schematics
Connector End View Reference
Cooling System Connector End Views
Description and Operation
Cooling System Description and Operation
Electrical Information Reference
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Circuit Testing
Connector Repairs
Testing for Intermittent Conditions and Poor Connections
Wiring Repairs
Scan Tool Reference
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Scan Tool Data List
Scan Tool Data Definitions
Diagnostic Aids
When checking the schematics and there is not any called out pinout numbers for the
relays, or relay connector end views. When reading the diagnostics the following must be
understood:
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Any circuit entering the relay from the power side or fuse side of the relay is
considered a Supply or B+ circuit. Examples: coil supply circuit, relay coil
B+,relay switch supply circuit, relay switch B+.
Any circuit leaving the relay at the relay and leaving the fuse block and going to
the module is considered a output control circuit. Examples: relay controlled
output circuit (switch side of relay) or, relay coil controlled circuit (coil side of
relay).
Due to the amount of diagnostic circuit call outs within the fuse block relay location and
the amount of relays involved an understanding of the relay pinout circuit function
locations must be understood. This vehicle carries no schematic pinout call outs per relay
to make the diagnostic naming easier. Understanding is based upon circuit function
naming.
Circuit/System Verification
1. Ignition ON, command the Fan 1 Relay output control ON and OFF with a scan
tool. Verify the fan low speed function turns ON and OFF with each command.
o If the fan low speed does not turn ON and OFF with each command,
proceed with the Low Speed Inoperative diagnostic.
o If the fan low speed remains ON at all times when commanding ON and
OFF, proceed with the Fans Always ON diagnostic.
2. Command the Fan Relays 1, & 2 output control ON and OFF with a scan tool.
Verify the fan high speed function turns ON and OFF with each command.
o If the fan high speed does not turn ON and OFF with each command,
proceed with the High Speed Inoperative diagnostic.
o If the fan high speed remains ON at all times when commanding ON and
OFF, proceed with the Fans Always ON diagnostic.
Circuit/System Testing
Low Speed Inoperative
1. Ignition OFF, disconnect the COOL/FAN 1 Relay.
2. Ignition ON, verify that a test lamp does not illuminate between the relay coil
control circuit terminal located in line with Underhood fuseblock pinout E10 side
of relay and ground.
o
If the test lamp illuminates, test the relay coil control circuit for a short to
voltage.
3. Verify that a test lamp illuminates between the COOL/FAN 1 Relay coil B+
circuit terminal and ground.
o If the test lamp does not illuminate, test the coil B+ circuit for a short to
ground or an open/high resistance. If the circuit tests normal and the B+
circuit fuse is open, test the COOL/FAN 1 Relay controlled output circuit
terminal, inline with the F10 side of the Underhood fuse block for a short
to ground. If the circuit tests normal, test or replace the cooling fan motor.
4. Verify that a test lamp illuminates between the COOL/FAN 1 Relay switch B+
circuit terminal and ground.
o If the test lamp does not illuminate, test the relay switch B+ for a short to
ground or an open/high resistance.
5. Connect a test lamp between the COOL/FAN 1 Relay switch B+ circuit terminal
and the relay coil control circuit terminal in line with the Underhood fuse block
pinout E10.
6. Command the Fan 1 Relay output ON and OFF with a scan tool. The test lamp
should turn ON and OFF when changing between the commanded states.
o If the test lamp is always OFF, test the Low Speed Cooling Fan Relay
control circuit for a short to voltage or an open/high resistance. If the
circuit tests normal, replace the ECM.
7. Connect a 40-amp fused jumper wire between the COOL/FAN 1 Relay switch B+
circuit terminal and the COOL/FAN 1 Relay controlled output circuit terminal.
8. Disconnect the harness connector at the Low Speed Winding of the Cooling Fan
Motor terminal 1.
9. Connect a test lamp between the Cooling Fan supply voltage circuit terminal 1
and ground. The test lamp should illuminate.
o If the test lamp does not illuminate, test the supply voltage circuit for an
open/high resistance. If the circuit tests normal, test or replace the
COOL/FAN 1 Relay.
10. Reconnect the harness connector at the cooling fan motor terminal 1 low speed
winding circuit.
11. Disconnect the harness connector at the Cooling Fan Motor ground circuit
terminal 3.
12. Ignition OFF, test for less than 1.0 ohm of resistance between the cooling fan
ground circuit terminal 3 and ground.
o If greater than 1.0 ohm, test the ground circuit for an open/high resistance.
13. Ignition ON, test for B+ between the cooling fan motor supply voltage circuit
terminal 1 and ground.
o If less than B+, test the cooling fan motor supply voltage circuit for a short
to ground or an open/high resistance. If the circuit tests normal, test or
replace the COOL/FAN 1 Relay.
14. If all circuits test normal, test or replace the Cooling Fan Motor.
High Speed Inoperative
1. Ignition OFF, disconnect the COOL/FAN 2 Relay.
2. Ignition ON, verify that a test lamp does not illuminate between the COOL/FAN
2 Relay coil control circuit terminal and ground.
o If the test lamp illuminates, test the relay coil control circuit for a short to
voltage.
3. Verify a test lamp illuminates between the relay coil B+ circuit terminal and
ground.
o If the test lamp does not illuminate, test the B+ circuit for a short to
ground or an open/high resistance. If the circuit tests normal and the B+
circuit fuse is open, test the relay controlled output circuit terminal for a
short to ground. If the circuit tests normal, test or replace the COOL/FAN
2 Relay.
4. Verify that a test lamp illuminates between the relay switch B+ terminal and
ground.
o If the test lamp does not illuminate, test the COOL/FAN 2 Relay switch
B+ for an open/high resistance.
5. Connect a test lamp between the COOL/FAN 2 Relay coil B+ circuit terminal and
the relay coil control circuit terminal.
6. Command the Fan Relays 2 & 3 output ON and OFF with a scan tool. The test
lamp should turn ON and OFF when changing between the commanded states.
o If the test lamp is always OFF, test the High Speed Relay control circuit
for a short to voltage or an open/high resistance. If the circuit tests normal,
replace the ECM.
7. Disconnect the harness connector at the Cooling Fan Motor High Speed Windings
terminal 2.
8. Ignition OFF, test for less than 1.0 ohm of resistance between the ground circuit
terminal 3 and ground.
o If greater than 1.0 ohm, test the ground circuit for an open/high resistance.
9. Connect the high speed winding harness connector terminal 2 at the Cooling Fan
Motor.
10. Ignition ON, connect a 40-amp fused jumper wire between the COOL/FAN 2
Relay switch B+ circuit terminal and the relay controlled output circuit terminal.
Verify the high speed cooling fan circuit is activated.
o If the high speed cooling fan does not activate, test the relay controlled
output circuit for an open/high resistance. If the circuit tests normal, test or
replace the cooling fan motor.
11. If all circuits test normal, test or replace the COOL/FAN 2 Relay.
Fans Always ON
1. Ignition OFF, disconnect the COOL/FAN 2 Relay.
2. Ignition ON, verify that a test lamp does not illuminate between the relay coil B+
circuit terminal and the relay controlled output circuit terminal.
o If the test lamp illuminates, test the relay controlled output circuit for a
short to ground. If all circuits test normal, replace the ECM.
3. Reconnect the COOL/FAN 2 Relay.
4. Disconnect the harness connector at the cooling fan motor.
5. Disconnect the COOL/FAN 1 Relay.
6. Verify that a test lamp does not illuminate between the COOL/FAN 1 Relay
switch B+ circuit terminal and the relay coil control circuit.
o If the test lamp illuminates, test the COOL/FAN 1 Relay controlled output
circuit for a short to ground. If all circuits test normal, replace the ECM.
7. Verify a test lamp does not illuminate between the COOL/FAN 1 Relay
controlled output circuit terminal and ground.
o If the test lamp illuminates, test the COOL/FAN 1 Relay output controlled
circuit for a short to B+.
8. If all circuits test normal, test or replace the COOL/FAN 1 Relay.
Component Testing
1. Ignition OFF, disconnect the affected relay.
2. Test for 60-180 ohms of resistance between terminals 85 and 86.
o If the resistance is not within the specified range, replace the relay.
3. Test for infinite resistance between the following terminals:
o 30 and 86
o 30 and 87
o 30 and 85
o 85 and 87
o If less than infinite, replace the relay.
4. Install a 20-amp fused jumper wire between relay terminal 85 and 12 volts. Install
a jumper wire between relay terminal 86 and ground. Test for less than 2.0 ohms
of resistance between terminals 30 and 87.
o If greater than 2.0 ohms, replace the relay.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
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Cooling Fan and Shroud Replacement
Relay Replacement
K20 Engine Control Module: Programming and Setup for ECM programming,
setup, and replacement.