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Home >> Chevrolet >> 2010 >> Cobalt L4-2.0L Turbo >> Repair and Diagnosis >> Engine, Cooling and Exhaust >> Cooling System >> Testing and Inspection >> Symptom Related Diagnostic Procedures >> Cooling Fan Inoperative

Cooling Fan Inoperative




Cooling Fan Inoperative (2.0L)

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 control module (ECM) commands 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.

In low speed operation, the ECM applies ground to the coil side of the cooling fan low speed relay. This energizes the coil and applies voltage directly to the right cooling fan through the switch side of the low speed relay. The right cooling fan is connected in series to the left cooling fan through the de-energized series/parallel (S/P) cooling fan speed control relay. The series circuit operates both fans at low speed.

In high speed operation, the ECM applies a ground to the coil side of the cooling fan low speed relay, the S/P cooling fan speed control relay, and the cooling fan high speed relay. When energized, the high speed fan relay applies voltage directly to the left cooling fan through the switch side of the relay. Simultaneously, the low speed fan relay and the S/P speed control relay provide ignition voltage and a direct path to ground for the right cooling fan. With both fans connected in a parallel circuit, each fan receives full voltage and operates at high 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

* KR20 cooling fan relay identification:

- KR20C low speed COOL FAN 1 Relay
- KR20D high speed COOL FAN 2 Relay
- KR20E speed control COOL FANS 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 (Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Cooling Fan Description and Operation (Cooling Fan Description and Operation)
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. DTC P0480, P0481, P0691, P0692, P0693 or P0694 should not be set.

• If a DTC is set, refer to DTC P0480, P0481, P0691, P0692, P0693, or P0694 (2.0L) (P0480).

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 all of the KR20 cooling fan relays.

Note: The jumper wire completes the right side fan ground circuit. Leave this jumper in place for the remainder of this procedure.

2. Connect a 30 A fused jumper between the KR20E relay switch circuit terminal 30 and the ground circuit terminal 87.

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 B+ circuit terminal listed below:

* KR20C COOL FAN 1 Relay Terminal 30
* KR20D COOL FAN 2 Relay Terminal 30

• 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 KR20 relay.

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 30 A fused jumper between the KR20 cooling fan relay circuit terminals listed below. Verify the appropriate fan is activated.

* KR20D COOL FAN 2 Relay Terminals 87 and 30
* KR20C COOL FAN 1 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.
• If the corresponding cooling fan activates, replace the appropriate KR20 cooling fan relay.

5. Install the KR20E speed control COOL FANS relay. Verify both fans activate at low speed.

• If both fans do not activate, test the relay controlled output circuit terminal 87A of the KR20E relay for a short to ground or an open/high resistance.

6. If all circuits test normal, test or replace the KR20E cooling fan speed control relay.

Component Testing

KR20 Cooling Fan Relay
1. Ignition OFF, disconnect the KR20 cooling fan relay.
2. Test for 70-110 ohm 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 O.L.

* 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 ohm between terminals 30 and 87A.

• If greater than the specified range, replace the KR20E cooling fan relay.

5. Install a 20 A fused jumper wire between relay terminal 85 and B+. Install 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 KR20 cooling fan relay.

G10L and G10R Engine Cooling Fan
1. Ignition OFF, disconnect the harness connector at the G10 engine cooling fan.
2. Connect a jumper wire between ground and the G10 ground circuit terminal 3.
3. Connect a 30 A fused jumper wire between B+ and the G10 B+ supply circuit terminal 1. The cooling fan should operate at a High speed:

• If the cooling fan does operate, replace the G10 engine cooling fan.

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))
* Cooling Fan and Shroud Replacement (Service and Repair)

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