Engine Cooling System: Other Chevrolet Malibu VI facelift

Cooling Fan - Right

Cooling Fan Connector Part Information (Right)

Cooling Fan Connector Terminal Identification (Right)

Reference Information

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

1. «Cooling System Component Views»(ref-269125-S32244811462007102900000)
2. «Cooling System Connector End Views»(ref-269125-S32637398132007102900000)
3. «Engine Control Module Connector End Views»(ref-269126-S35839133202007102900000)

Description and Operation

Cooling Fan Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-269145-S07499872622007102900000)
2. «Connector Repairs»(ref-269145-S03006904552007102900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-269145-S26826198002007102900000)
4. «Wiring Repairs»(ref-269145-S33888156582007102900000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

1. «Scan Tool Data List»(ref-269188-S23883026652007102900000)
2. «Scan Tool Data Definitions»(ref-269188-S41513144292007102900000)
3. «Scan Tool Output Controls»(ref-269188-S19966316012007102900000)

Circuit/System Verification

Ignition ON, command each relay ON and OFF with a scan tool. Feel or listen to verify that each relay turns ON and OFF with each command.

Repair Procedures

1. Perform the «Diagnostic Repair Verification»(ref-269144-S42854858042007102900000) after completing the diagnostic procedure.
2. «Cooling Fan and Shroud Replacement (L61)»(ref-269125-S07816009012007102900000) or «Cooling Fan and Shroud Replacement (LZ4, LZ9)»(ref-269125-S16463243962007102900000)
3. «Engine Control Module Replacement»(ref-269126-S21673745592007102900000)

Description and Operation

1. «Cooling System Description and Operation»(ref-269125-S10439631092007102900000)
2. «Instrument Cluster Description and Operation»(ref-269119-S30237595622007102900000)
3. «Indicator/Warning Message Description and Operation»(ref-269119-S32712329452007102900000)
4. «Audible Warnings Description and Operation»(ref-269119-S42050805382007102900000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

1. «Scan Tool Data List»(ref-269125-S03071708112007102900000)
2. «Scan Tool Data Definitions»(ref-269125-S22238270612007102900000)
3. «Scan Tool Output Controls»(ref-269125-S37642081472007102900000)

1. If DTC P0480 or P0481 are set, diagnose those DTCs first.
2. Observe the engine coolant level. The engine coolant level should be within the operating range. Refer to Capacities - Approximate Fluid, and Engine Coolant in the Owner's Manual.
3. Ensure that the vehicle has the correct engine coolant with correct concentration and is not old, contaminated, or contains additives. Refer to Recommended Fluids and Lubricants in the Owner's Manual.
4. Inspect the cooling system for the following: Leaks Kinked or pinched hoses, especially at the radiator Loose, missing, or damaged radiator air seals or deflectors Air flow obstructions or bent fins at the radiator or the A/C condenser. Refer to «Symptoms - Engine Cooling»(ref-269125-S23741126432007102900000) .
5. Command the cooling fans ON and OFF, low and high speed. The engine cooling fans should turn ON and OFF with each command. If the cooling fans do not function as indicated, refer to «Cooling Fan Inoperative»(ref-269125-S09956018882007102900000) .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Identifying Intermittent Conditions

Many intermittent conditions occur with harness or connector movement due to engine torque, rough pavement, vibration or physical movement of a component. Refer to the following for a list to help determine an intermittent condition

1. Moisture and water intrusion in connectors, terminals, and components
2. Connector mating
3. Terminal contact
4. High circuit or component resistance-High resistance can include any resistance, regardless of the amount, which can interrupt the operation of the component.
5. Harness that is located too tight, or chaffed circuits
6. High or low ambient temperature
7. High or low engine coolant temperatures
8. High underhood temperatures
9. Heat build up in component or circuit due to circuit resistance, poor terminal contact, or high electrical load
10. High or low system voltage
11. High vehicle load conditions
12. Rough road surface
13. Electro-magnetic interference (EMI)/circuit interference from relays, solenoids or other electrical surge
14. Incorrect installation of non-factory, aftermarket, and after factory add on accessories

If an intermittent is determined, refer to Testing for Intermittent Conditions and Poor Connections for specific strategies in diagnosing intermittent conditions.

Perform the Diagnostic Repair Verification after completing the repair.

1. «Engine Overheating»(ref-269125-S29746478592007102900000)
2. «Instrument Cluster Replacement»(ref-269119-S40889049132007102900000)

Repair Verification

Verify that the ECT indicator is OFF while the engine is operating.

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

Cooling System Connector End Views

Description and Operation

Cooling System Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-269145-S07499872622007102900000)
2. «Connector Repairs»(ref-269145-S03006904552007102900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-269145-S26826198002007102900000)
4. «Wiring Repairs»(ref-269145-S33888156582007102900000)

Scan Tool Reference

Scan Tool Data List

Scan Tool Output Controls

Turn ON the ignition with the engine OFF.

Command the instrument cluster indicators ON and OFF with a scan tool.

The low coolant indicator lamp should turn ON and OFF on command.

The low coolant indicator should be OFF with the engine coolant at the proper level.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Surge Tank Replacement»(ref-269125-S13088190842007102900000)
2. «Control Module References»(ref-269146-S40400118222007102900000)
3. «Instrument Cluster Replacement»(ref-269119-S40889049132007102900000)

Verify that the low coolant indicator is OFF with the engine coolant at the proper level.

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

1. «Cooling System Component Views»(ref-269125-S32244811462007102900000)
2. «Cooling System Connector End Views»(ref-269125-S32637398132007102900000)
3. «Engine Control Module Connector End Views»(ref-269126-S35839133202007102900000)

Description and Operation

Cooling Fan Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-269145-S07499872622007102900000)
2. «Connector Repairs»(ref-269145-S03006904552007102900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-269145-S26826198002007102900000)
4. «Wiring Repairs»(ref-269145-S33888156582007102900000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

1. «Scan Tool Data List»(ref-269188-S23883026652007102900000)
2. «Scan Tool Data Definitions»(ref-269188-S41513144292007102900000)
3. «Scan Tool Output Controls»(ref-269188-S19966316012007102900000)

1. Verify that the following DTCs are not set: P0480, P0481. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(ref-269144-S09308816252007102900000) .
2. Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
3. Ignition ON, observe that the fans are not activated.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Cooling Fan and Shroud Replacement (L61)»(ref-269125-S07816009012007102900000) or «Cooling Fan and Shroud Replacement (LZ4, LZ9)»(ref-269125-S16463243962007102900000)
2. «Engine Control Module Replacement»(ref-269126-S21673745592007102900000)

1. Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
2. Ignition ON, observe that the fan is not activated.

Schematic Reference

Engine Cooling Schematics

Connector End View Reference

1. «Cooling System Component Views»(ref-269125-S32244811462007102900000)
2. «Cooling System Connector End Views»(ref-269125-S32637398132007102900000)
3. «Engine Control Module Connector End Views»(ref-269126-S35839133202007102900000)

Description and Operation

Cooling Fan Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-269145-S07499872622007102900000)
2. «Connector Repairs»(ref-269145-S03006904552007102900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-269145-S26826198002007102900000)
4. «Wiring Repairs»(ref-269145-S33888156582007102900000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

1. «Scan Tool Data List»(ref-269188-S23883026652007102900000)
2. «Scan Tool Data Definitions»(ref-269188-S41513144292007102900000)
3. «Scan Tool Output Controls»(ref-269188-S19966316012007102900000)

1. If DTCs P0480 or P0481 are set, then perform those diagnostics first.
2. Ignition ON, command each relay ON and OFF with a scan tool. Observe to verify that the fan turns ON and OFF with each command.

1. Perform the «Diagnostic Repair Verification»(ref-269144-S42854858042007102900000) after completing the diagnostic procedure.
2. «Cooling Fan and Shroud Replacement (L61)»(ref-269125-S07816009012007102900000) or «Cooling Fan and Shroud Replacement (LZ4, LZ9)»(ref-269125-S16463243962007102900000)
3. «Engine Control Module Replacement»(ref-269126-S21673745592007102900000)

Ignition ON, command each relay ON and OFF with a scan tool. Observe to verify that the fans turn ON and OFF with each command.

Engine Overheating

Engine Overheating

Loss of Coolant

Loss of Coolant

Electrical Information Reference

1. «Circuit Testing»(ref-269145-S07499872622007102900000)
2. «Connector Repairs»(ref-269145-S03006904552007102900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-269145-S26826198002007102900000)
4. «Wiring Repairs»(ref-269145-S33888156582007102900000)

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Coolant Heater Replacement (L61)»(ref-269125-S01568120912007102900000) or «Coolant Heater Replacement (LZ4/LZ9)»(ref-269125-S36199742622007102900000)
2. «Coolant Heater Cord Replacement (L61)»(ref-269125-S08375427562007102900000) or «Coolant Heater Cord Replacement (LZ4)»(ref-269125-S04161903562007102900000) or «Coolant Heater Cord Replacement (LZ9)»(ref-269125-S25263015132007102900000)

Engine Fails To Reach Normal Operating Temperature

Engine Fails To Reach Normal Operating Temperature

Tools Required

J 26568 Coolant and Battery Fluid Tester. See Special Tools .

Fill Procedure

1. Install the engine block coolant drain plugs. Refer to «Engine Block Assemble»(ref-269140-S20558758442007102900000) for the 3.5L engine or «Engine Block Assemble»(ref-269140-S20558758442007102900000) for the 3.9L engine.
2. Close the radiator drain plug.
3. Lower the vehicle.
4. Vehicle should be level.
5. Add a mixture of 50/50 DEX-COOL® antifreeze and clean drinkable water until the level stabilizes approximately 1 in (25.4 mm) above the weld seam on the surge tank Refer to «Capacities - Approximate Fluid»(ref-269187-S10411133212007102900000) .
6. Install the surge tank cap.
7. Start the engine and run at 2,000 RPM until the engine cooling fans turn ON.
8. Let the engine idle for 30 seconds.
9. Turn the engine OFF and allow the engine to cool down.
10. Remove the surge tank cap.
11. Refill to approximately 1 in (25.4 mm) above the weld seam on the surge tank.
12. Inspect the concentration of the engine coolant using J 26568 . See «Special Tools»(ref-269125-S38308891652007102900000) .
13. Install the surge tank cap.
14. Rinse away any excess coolant from the engine and the engine compartment.

Vac N Fill Procedure

If a complete engine block drain was required, install the engine block drain plugs. Refer to the appropriate procedure

1. «Engine Block Assemble»(ref-269139-S08044628192007102900000) for the 2.2L engine
2. «Engine Block Assemble»(ref-269140-S20558758442007102900000) for the 3.5L engine
3. «Engine Block Assemble»(ref-269140-S20558758442007102900000) for the 3.9L engine

1. Install J-42401-2 into the surge tank fill neck.
2. Install J-42401-3 to the surge tank fill neck.
3. Attach the Vac N Fill cap to the J-42401-3.
4. Attach the Vac N Fill cap to the vehicles coolant fill port.
5. Attach the vacuum gage assembly to the Vac N Fill cap.
6. Attach the fill hose to the barb fitting on the vacuum gage assembly. Ensure the valve is closed.
7. Pour the coolant mixture into the graduated reservoir.
8. Place the fill hose in the graduated reservoir.
9. Install the vacuum tank on the graduated reservoir with the fill hose routed through the cut-out area in the vacuum tank.
10. Attach the venturi assembly to the vacuum tank.
11. Attach a shop air hose to the venturi assembly. Ensure the valve on the venturi assembly is closed.
12. Attach the vacuum hose to the vacuum gage assembly and the vacuum tank.
13. Open the valve on the venturi assembly. The vacuum gage will begin to rise and a hissing noise will be present.
14. Continue to draw vacuum until the needle stops rising. This should be 610-660 mm Hg (24-26 in Hg). Cooling hoses may start to collapse. This is normal due to vacuum draw.
15. To aid in the fill process, position the graduated reservoir above the coolant fill port.
16. Slowly open the valve on the vacuum gage assembly. When the coolant reaches the top of the fill hose, close the valve. This will eliminate air from the fill hose.
17. Close the valve on the venturi assembly.
18. If there is a suspected leak in the cooling system, allow the system to stabilize under vacuum and monitor for vacuum loss. If vacuum loss is observed, refer to «Loss of Coolant»(ref-269125-S18020681642007102900000) .
19. Open the valve on the vacuum gage assembly. The vacuum gage will drop as coolant is drawn into the system.
20. Once the vacuum gage reaches zero, close the valve on the vacuum gage assembly and repeat steps 11-17.
21. Remove the J-42401-3 from the surge tank fill neck.
22. Remove J-42401-2 from the surge tank fill neck.
23. Detach the Vac N Fill cap from the vehicles coolant fill port.
24. Add coolant to the system as necessary.
25. Inspect the concentration of the coolant mixture using J 26568 . See «Special Tools»(ref-269125-S38308891652007102900000) .
26. Detach the vacuum hose from the vacuum gage assembly.
27. Attach the extraction hose to the vacuum hose.
28. Open the valve on the venturi assembly to start a vacuum draw.
29. Use the extraction hose to draw out coolant to the proper level.
30. Install the surge tank cap.
31. The vacuum tank has a drain valve on the bottom of the tank. Open the valve to drain coolant from the vacuum tank into a suitable container for disposal.

J 26568 Coolant and Battery Fluid Tester. See Special Tools .

1. Close the radiator drain plug.
2. Close the water pump drain plug. Refer to «Water Pump Installation»(ref-269139-S25085962232007102900000) for the 2.2L.(L61) engine.
3. Lower the vehicle.
4. Vehicle should be level.
5. Add a mixture of 50/50 DEX-COOL® antifreeze and clean drinkable water until the level stabilizes approximately 25.4 mm (1.0 in) above the weld seam on the surge tank. Refer to «Capacities - Approximate Fluid»(ref-269187-S10411133212007102900000) .
6. Install the surge tank cap.
7. Start the engine and run at 2,000 RPM until the engine cooling fans turn ON.
8. Turn the engine OFF and allow the engine to cool down.
9. Remove the surge tank cap.
10. Refill to approximately 25.4 mm (1.0 in) above the weld seam on the surge tank.
11. Inspect the concentration of engine coolant using J 26568 . See «Special Tools»(ref-269125-S38308891652007102900000) .
12. Install the surge tank cap.
13. Rinse away any excess coolant from the engine and the engine compartment.

Radiator Cleaning

Note. The radiator fins are necessary for good heat transfer. Do not brush the fins. This may cause damage to the fins, reducing heat transfer.

1. Some conditions may require the use of warm water and a mild detergent.
2. Clean the A/C condenser fins.
3. Clean between the A/C condenser and radiator.
4. Clean the radiator cooling fins.
5. Straighten any damaged cooling fins.

Scheme 15

Surge Tank Replacement

Scheme 16

Surge Tank Hose/Pipe Replacement - Inlet (LZ4, LZ9)

J 38185 Hose Clamp Pliers. See Special Tools .

J 38185 Hose Clamp Pliers. See Special Tools .

J 38185 Hose Clamp Pliers. See Special Tools .

J 38185 Hose Clamp Pliers. See Special Tools .

J 38185 Hose Clamp Pliers. See Special Tools .

Scheme 17

Scheme 18

Scheme 19

Scheme 20

Scheme 21

Scheme 22

1. Drain the coolant. Refer to «Draining and Filling Cooling System (LZ4, LZ9)»(ref-269125-S06783192392007102900000) or «Draining and Filling Cooling System (GE 47716)»(ref-269125-S30645193322007102900000) or «Draining and Filling Cooling System (L61)»(ref-269125-S21497493672007102900000) .
2. Remove the left headlamp. Refer to «Headlamp Assembly or Headlamp Bulb and/or Cornering, Sidemarker, Park, Turn Signal Bulb Replacement»(ref-269116-S14799649512007102900000) .
3. Remove the right headlamp. Refer to «Headlamp Assembly or Headlamp Bulb and/or Cornering, Sidemarker, Park, Turn Signal Bulb Replacement»(ref-269116-S14799649512007102900000) .
4. Loop a rope around each of the 2 tabs of the condenser and tie the rope around the upper tie bar.
5. Remove the upper radiator support bracket bolts.
6. Remove the upper radiator support brackets.
7. Reposition the radiator outlet hose clamp at the radiator using the J 38185 . See «Special Tools»(ref-269125-S38308891652007102900000) .
8. Remove the radiator outlet hose from the radiator.
9. Reposition the radiator inlet hose clamp at the radiator using the J 38185 . See «Special Tools»(ref-269125-S38308891652007102900000) .
10. Remove the radiator inlet hose from the radiator.
11. Raise the vehicle. Refer to «Lifting and Jacking the Vehicle»(ref-269115-S22909578032007102900000) .
12. Remove the lower radiator air deflector retainers.
13. Remove the lower radiator air deflector.
14. Remove the right front fender liner. Refer to «Front Fender Liner Replacement»(ref-269113-S28080045772007102900000) .
15. Remove the right radiator air deflector retainers.
16. Remove the right radiator air deflector.
17. Remove the left radiator air deflector retainers.
18. Remove the left radiator air deflector.
19. Place a drain pan under the transmission oil cooler pipes.
20. Remove the transmission oil cooler pipes attachment nut from the transmission.
21. Remove the transmission oil cooler pipes from the transmission.
22. Remove the lower radiator support bracket bolts.
23. Remove the lower radiator support brackets.
24. Remove the radiator lower mounts.
25. Remove and discard the condenser mounting bolts.
26. Push upward on the radiator and downward on the condenser to unsnap the condenser mounting tabs from the radiator clips.
27. Remove and discard the condenser mounting nuts from the radiator.
28. Remove the radiator air side seals.
29. Remove the radiator, cooling fan shroud and transmission oil cooler pipe assembly.
30. Remove the transmission oil cooler pipes from the radiator. Refer to «Transmission Fluid Cooler Hose/Pipe Quick-Connect Fitting Replacement»(ref-269107-S11845836702007102900000) .
31. Pry upward on the fan shroud tabs at the radiator clips.
32. Remove the cooling fan and shroud assembly from the radiator.

Scheme 23

1. Install the cooling fan and shroud assembly to the radiator.
2. Snap the fan shroud tabs into the radiator clips.
3. Install the transmission oil cooler pipes to the radiator. Refer to «Transmission Fluid Cooler Hose/Pipe Quick-Connect Fitting Replacement»(ref-269107-S11845836702007102900000) .
4. Install the radiator, cooling fan shroud and transmission oil cooler pipe assembly.
5. Install the radiator air side seals onto the condenser mounting tabs on the radiator.
6. Install the condenser mounting nuts to the radiator.
7. Insert the condenser mounting tabs into the radiator clips.
8. Install the condenser mounting bolts. Tighten: Tighten the bolts to 6 N.m (53 lb in).
9. Bend the radiator air side seals and insert the seals into the channel of the intake air splash shields.
10. The radiator air side seals must be in the proper position for proper air flow.
11. Install the radiator lower mounts.
12. Install the lower radiator support brackets.
13. Install the lower radiator support bracket bolts. Tighten: Tighten the bolts to 60 N.m (44 lb ft).
14. Install the transmission oil cooler pipes to the transmission.
15. Install the transmission oil cooler pipes attachment nut to the transmission. Tighten: Tighten the nut to 7 N.m (62 lb in).
16. Install the left radiator air deflector.
17. Install the left radiator air deflector retainers.
18. Install the right radiator air deflector.
19. Install the right radiator air deflector retainers.
20. Install the right front fender liner. Refer to «Front Fender Liner Replacement»(ref-269113-S28080045772007102900000) .
21. Install the lower radiator air deflector.
22. Install the lower radiator air deflector retainers.
23. Lower the vehicle.
24. Install the radiator inlet hose to the radiator.
25. Reposition the radiator inlet hose clamp at the radiator using the J 38185 . See «Special Tools»(ref-269125-S38308891652007102900000) .
26. Install the radiator outlet hose to the radiator.
27. Reposition the radiator outlet hose clamp at the radiator using the J 38185 . See «Special Tools»(ref-269125-S38308891652007102900000) .
28. Remove the rope attached to the condenser and upper tie bar.
29. Install the upper radiator support brackets.
30. Install the upper radiator support bracket bolts. Tighten: Tighten the bolts to 10 N.m (89 lb in).
31. Install the right headlamp. Refer to «Headlamp Assembly or Headlamp Bulb and/or Cornering, Sidemarker, Park, Turn Signal Bulb Replacement»(ref-269116-S14799649512007102900000) .
32. Install the left headlamp. Refer to «Headlamp Assembly or Headlamp Bulb and/or Cornering, Sidemarker, Park, Turn Signal Bulb Replacement»(ref-269116-S14799649512007102900000) .
33. Fill the coolant. Refer to «Draining and Filling Cooling System (LZ4, LZ9)»(ref-269125-S06783192392007102900000) or «Draining and Filling Cooling System (GE 47716)»(ref-269125-S30645193322007102900000) or «Draining and Filling Cooling System (L61)»(ref-269125-S21497493672007102900000) .
34. Inspect the transmission fluid level. Refer to «Transmission Fluid Checking»(ref-269185-S00278012722007102900000) .

J 38185 Hose Clamp Pliers. See Special Tools .

Cooling Fan Control

The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) or engine control module (ECM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the underhood fuse block. The ground path is provided at G106.

During low speed operation, the PCM/ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage from the cool fan 1 fuse through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan S/P relay and the right cooling fan. The result is a series circuit with both fans running at low speed.

During high speed operation the PCM/ECM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3 second delay, the PCM/ECM supplies a ground path for the cooling fan 2 relay and the cooling fan S/P relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 2 relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling fan S/P relay coil is energized closing the relay contacts and provides battery positive voltage from the cool fan 2 fuse on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have their own ground path. The result is a parallel circuit with both fans running at high speed.

The PCM/ECM commands Low Speed Fans on under the following conditions

1. Engine coolant temperature exceeds approximately 106°C (223°F).
2. When A/C is requested and the ambient temperature is more than 50°C (122°F).
3. A/C refrigerant pressure exceeds 1 310 kPa (190 psi).
4. After the vehicle is shut off if the engine coolant temperature at key-off is more than 140°C (284°F) and system voltage is more than 12 volts. The fans will stay on for approximately 3 minutes.

The PCM/ECM commands High Speed Fans on under the following conditions

1. Engine coolant temperature reaches 110°C (230°F).
2. A/C refrigerant pressure exceeds 1 655 kPa (240 psi).
3. When certain DTCs set

The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) or engine control module (ECM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the underhood fuse block. The ground path is provided at G106.

During low speed operation, the PCM/ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage from the cool fan 1 fuse through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan S/P relay and the right cooling fan. The result is a series circuit with both fans running at low speed.

During high speed operation the PCM/ECM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3 second delay, the PCM/ECM supplies a ground path for the cooling fan 2 relay and the cooling fan S/P relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 2 relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling fan S/P relay coil is energized closing the relay contacts and provides battery positive voltage from the cool fan 2 fuse on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have their own ground path. The result is a parallel circuit with both fans running at high speed.

The PCM/ECM commands Low Speed Fans on under the following conditions

1. Engine coolant temperature exceeds approximately 106°C (223°F).
2. When A/C is requested and the ambient temperature is more than 50°C (122°F).
3. A/C refrigerant pressure exceeds 1 310 kPa (190 psi).
4. After the vehicle is shut off if the engine coolant temperature at key-off is more than 140°C (284°F) and system voltage is more than 12 volts. The fans will stay on for approximately 3 minutes.

The PCM/ECM commands High Speed Fans on under the following conditions

1. Engine coolant temperature reaches 110°C (230°F).
2. A/C refrigerant pressure exceeds 1 655 kPa (240 psi).
3. When certain DTCs set

Engine Coolant Indicators

TEMP

1. The instrument panel cluster (IPC) illuminates the TEMP indicator when the powertrain control module (PCM) or engine control module (ECM) determines that the coolant temperature is more than 128°C (262°F). The IPC receives a discrete input from the PCM/ECM requesting illumination.
2. The IPC performs the display test at the start of each ignition cycle. The IPC illuminates the TEMP indicator.

Coolant Level Control

The engine cooling system contains an engine coolant level switch to alert the driver in the event of a low coolant level. When the engine coolant level in the coolant recovery reservoir falls below a certain level, the coolant level switch opens. When the body control module (BCM) detects an open or a high voltage level on the coolant level indicator control circuit, for at least 10 seconds, it will send a GM LAN message to the driver information center (DIC) requesting display of the low coolant level message. There is approximately a 10 second delay before the BCM sends the GM LAN message to prevent the message from being displayed, due to coolant sloshing in the surge tank.

Coolant Heater

The optional engine coolant heater (RPO K05) operates using AC external power and is designed to warm the coolant in the engine block area for improved starting in very cold weather -29°C (-20°F). The coolant heater helps reduce fuel consumption when a cold engine is warming up. The unit is equipped with a detachable AC power cord. A weather shield on the cord is provided to protect the plug when not in use.

The cooling systems function is to maintain an efficient engine operating temperature during all engine speeds and operating conditions. The cooling system is designed to remove approximately one-third of the heat produced by the burning of the air-fuel mixture. When the engine is cold, the coolant does not flow to the radiator until the thermostat opens. This allows the engine to warm quickly.

Cooling Cycle

Coolant flows from the radiator outlet and into the water pump inlet. Some coolant flows from the water pump, to the heater core, then back to the water pump. This provides the passenger compartment with heat and defrost capability as the coolant warms up.

Coolant also flows from the water pump outlet and into the engine block. In the engine block, the coolant circulates through the water jackets surrounding the cylinders where the coolant absorbs heat.

The coolant then flows through the cylinder head gasket openings and into the cylinder heads. In the cylinder heads, the coolant flows through the water jackets surrounding the combustion chambers and valve seats, where the coolant absorbs additional heat.

From the cylinder heads, the coolant flows to the thermostat. The flow of coolant will either be stopped at the thermostat until the engine reaches normal operating temperature, or the coolant will flow through the thermostat and into the radiator where the coolant is cooled. At this point, the coolant flow cycle is completed.

Efficient operation of the cooling system requires proper functioning of all cooling system components. The cooling system consists of the following components.

Coolant

The engine coolant is a solution made up of a 50/50 mixture of DEX-COOL and suitable drinking water. The coolant solution carries excess heat away from the engine to the radiator, where the heat is dissipated to the atmosphere.

Radiator

The radiator is a heat exchanger consisting of a core and 2 tanks. The aluminum core is a tube and fin crossflow design that extends from the inlet tank to the outlet tank. Fins are placed around the outside of the tubes to improve heat transfer to the atmosphere.

The inlet and outlet tanks are a molded, high temperature, nylon reinforced plastic material. A high temperature rubber gasket seals the tank flange edge to the aluminum core. The tanks are clamped to the core with clinch tabs. The tabs are part of the aluminum header at each end of the core.

The radiator also has a drain cock located in the bottom of the end tank. The drain cock unit includes the drain cock and drain cock seal.

Heat is removed from the coolant as the coolant passes through the radiator. The fins on the core transfer heat from the coolant passing through the tubes. Air passing between the fins absorbs the heat and cools the coolant.

Pressure Cap

The pressure cap seals and pressurizes the cooling system. The cap contains a blow off, or pressure valve and a vacuum, or an atmospheric valve

1. The pressure valve is held against the seat by a spring that protects the radiator by relieving pressure that exceeds 15 psi.
2. The vacuum valve is held against the seat by a spring that permits opening of the valve to relieve vacuum created when the cooling system cools. The vacuum, if not relieved, might cause the radiator to collapse.

The pressure cap allows the cooling system pressure to build up when the temperature increases. As the pressure builds, the boiling point of the coolant increases. Therefore, the engine coolant can be safely run at a temperature much higher than the boiling point of the coolant at atmospheric pressure. The hotter the coolant becomes, the faster the heat transfers from the radiator into the cooler air.

The pressure in the cooling system can get too high. When the pressure exceeds the strength of the spring, the pressure valve rises, venting the excess pressure.

As the engine cools, the temperature of the coolant drops and a vacuum is created in the cooling system. This vacuum causes the vacuum valve to open. This equalizes the pressure in the cooling system with the atmospheric pressure, preventing the radiator from collapsing.

Coolant Recovery System

The coolant recovery system consists of a plastic coolant recovery reservoir and overflow tube. The recovery reservoir is also called a recovery tank or expansion tank. This tank is partially filled with coolant and is connected to the radiator fill neck with the overflow tube. Coolant can flow back and forth between the radiator and the reservoir.

In effect, a cooling system with a coolant recovery reservoir is a closed system. When the pressure within the cooling system gets too high, the pressure valve in the pressure cap will open. This allows the coolant, which has expanded due to heat, to flow through the overflow tube and into the recovery reservoir. As the engine cools down, the temperature of the coolant drops and a vacuum is created in the cooling system. This vacuum opens the vacuum valve in the pressure cap, allowing some of the coolant in the reservoir to be siphoned back into the radiator. Under normal operating conditions, no coolant is lost. Although the coolant level in the recovery reservoir goes up and down, the radiator and cooling system are kept full. An advantage to using a coolant recovery reservoir is the elimination of almost all air bubbles from the cooling system. Coolant without bubbles absorbs heat much better than coolant with bubbles.

Air Baffles and Seals

The cooling system uses deflectors, air baffles and air seals to increase cooling system capability. Deflectors are installed under the vehicle to redirect airflow beneath the vehicle and through the radiator to increase engine cooling. Air baffles are also used to direct airflow through the radiator and increase cooling capability. Air seals prevent air from bypassing the radiator and A/C condenser, and prevent recirculation of hot air for better hot weather cooling and A/C condenser performance.

Water Pump

The water pump is a centrifugal vane impeller type pump. The pump consists of a housing with coolant inlet and outlet passages and an impeller. The impeller is a flat plate mounted on the pump shaft with a series of flat or curved blades or vanes. When the impeller rotates, the coolant between the vanes is thrown outward by centrifugal force. The impeller shaft is supported by one or more sealed bearings, which never need to be lubricated. With a sealed bearing, grease cannot leak out, and dirt and water cannot get in.

The water pump circulates coolant throughout the cooling system. The pump is driven by the crankshaft from the drive belt.

Thermostat

The thermostat is a coolant flow control component, whose purpose is to regulate the operating temperature of the engine. The thermostat utilizes a temperature sensitive wax-pellet element, which connects to a valve through a piston. Heating causing the element to expand and exert pressure against a rubber diaphragm. This pressure forces the valve to open. Cooling causes the element to contract. This contraction allows a spring to push the valve closed.

When the coolant temperature is below 91°C (195°F), the thermostat valve remains closed. This prevents circulation of the coolant to the radiator and allows the engine to warm up quickly. After the coolant temperature reaches 91°C (195°F), the thermostat valve will open. The coolant is then allowed to circulate through the thermostat to the radiator where the engine heat is dissipated to the atmosphere. The thermostat also provides a restriction in the cooling system, even after opening. This restriction creates a pressure difference which prevents cavitation at the water pump and forces coolant to circulate through the engine block.

Engine Oil Cooler

The engine oil cooler is a heat exchanger which is located external to the radiator. The oil temperature is cooled by the air passing through the oil cooler fins. The oil pump pumps the oil through the feed line to the oil cooler. The oil flows through the cooler where the air absorbs heat from the oil. The oil is then pumped through the cooler return line to the oil filter and returns to the main oil passage.

Transmission Oil Cooler - Internal

The transmission oil cooler is a heat exchanger that is located inside one of the radiator end tanks. The transmission fluid temperature is regulated by the temperature of the engine coolant in the radiator. The oil pump pumps the fluid through the transmission oil cooler feed line to the oil cooler. The fluid flows through the cooler where the engine coolant absorbs heat from the fluid. The fluid is then pumped through the oil cooler return line back to the transmission.

Transmission Oil Cooler - External

The transmission oil cooler is a heat exchanger that is located external to the radiator. Air passing through the oil cooler fins cools the transmission fluid temperature. Within the transmission system, the oil pump pumps the fluid through the feed line to the oil cooler. The fluid then flows through the cooler where air absorbs heat from the fluid. The fluid is then pumped through the oil cooler return line back to the transmission.