Reference Information
Schematic Reference
Engine Cooling Schematics
Connector End View Reference
- «Component Connector End Views»(ref-299146-S19819642422008092200000)
- «Powertrain Component Views»(ref-299189-S03306127822008092200000)
Description and Operation
Cooling Fan Description and Operation (w/o LFA)
Electrical Information Reference
- «Circuit Testing»(ref-299147-S03573486312008092200000)
- «Connector Repairs»(ref-299147-S42810647942008092200000)
- «Testing for Intermittent Conditions and Poor Connections»(ref-299147-S22629174232008092200000)
- «Wiring Repairs»(ref-299147-S14041193842008092200000)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References
Circuit/System Verification
- Verify with a scan tool that the ECM is not commanding fan relay activation.
- 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.
- Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Repair Procedures
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- «Relay Replacement (Attached to Wire Harness)»(ref-299149-S36687121022008092200000) or «Relay Replacement (Within an Electrical Center)»(ref-299149-S33515372162008092200000)
- «Underhood Electrical Center or Junction Block Replacement»(ref-299149-S02703678252008092200000)
- «Engine Cooling Fan Replacement»(ref-299178-S04860373932008092200000)
- «Control Module References»(ref-299148-S19965029262008092200000) for ECM replacement, setup, and programming
| IMPORTANT | Review the system operation in order to familiarize yourself with the system functions. Refer to the following: Cooling System Description and Operation Cooling Fan Description and Operation (w/o LFA) |
Intermittent
Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections .
Schematic Reference
Engine Cooling Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Cooling Fan Description and Operation (w/o LFA)
Electrical Information Reference
- «Circuit Testing»(ref-299147-S03573486312008092200000)
- «Connector Repairs»(ref-299147-S42810647942008092200000)
- «Testing for Intermittent Conditions and Poor Connections»(ref-299147-S22629174232008092200000)
- «Wiring Repairs»(ref-299147-S14041193842008092200000)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
- 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-299145-S24801518742008092200000) .
- Verify with a scan tool that the ECM is not commanding fan relay activation.
- Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
- Ignition ON, observe that the fans are not activated.
- «Relay Replacement (Attached to Wire Harness)»(ref-299149-S36687121022008092200000) or «Relay Replacement (Within an Electrical Center)»(ref-299149-S33515372162008092200000)
- «Underhood Electrical Center or Junction Block Replacement»(ref-299149-S02703678252008092200000)
- «Engine Cooling Fan Replacement»(ref-299178-S04860373932008092200000)
- «Control Module References»(ref-299148-S19965029262008092200000) for ECM replacement, setup, and programming
Repair Verification
- Ignition ON, verify with a scan tool that the ECM is not commanding fan activation.
- Ignition ON, observe that the fan is not activated.
Schematic Reference
Engine Cooling Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Cooling Fan Description and Operation (w/o LFA)
Electrical Information Reference
- «Circuit Testing»(ref-299147-S03573486312008092200000)
- «Connector Repairs»(ref-299147-S42810647942008092200000)
- «Testing for Intermittent Conditions and Poor Connections»(ref-299147-S22629174232008092200000)
- «Wiring Repairs»(ref-299147-S14041193842008092200000)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
- If DTCs P0480 or P0481 are set, perform those diagnostics first.
- Verify with a scan tool that the ECM is not commanding fan relay activation.
- 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.
- «Relay Replacement (Attached to Wire Harness)»(ref-299149-S36687121022008092200000) or «Relay Replacement (Within an Electrical Center)»(ref-299149-S33515372162008092200000)
- «Underhood Electrical Center or Junction Block Replacement»(ref-299149-S02703678252008092200000)
- «Engine Cooling Fan Replacement»(ref-299178-S04860373932008092200000)
- «Control Module References»(ref-299148-S19965029262008092200000) for ECM replacement, setup, and programming
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
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Inspect for a missing or damaged radiator side or upper baffle and/or radiator air deflector. Is the baffle and/or deflector missing or damaged? | Go to Step 8 | Go to Step 2 |
| 2 | Inspect for a loss of coolant. Is there a loss of coolant? | Go to Step 3 | Go to Step 4 |
| 3 | Fill the system to the specified level. Does the engine overheat? | Go to Step 4 | System OK |
| 4 | Inspect for low temperature protection. Is the coolant to the correct concentration? | Go to Step 5 | Go to Step 8 |
| 5 | Inspect for a loss of cooling system pressure. Is there a loss of system pressure? | Go to Step 8 | Go to Step 6 |
| 6 | Inspect for a faulty engine coolant temperature (ECT) sensor. Refer to DTC P0117 or P0118 . Is the sensor operating properly? | Go to Step 7 | Go to Step 8 |
| 7 | Inspect for the following: Damaged coolant surge tank Leaking hose Bad/incorrect surge tank or radiator cap Were any of the above found? | Go to Step 8 | Go to Step 10 |
| 8 | Repair or install new parts as necessary, then retest. Does the engine overheat? | Go to Step 9 | System OK |
| 9 | Inspect for incorrect drive belt tension. Is the belt tension correct? | Go to Step 10 | Go to Step 8 |
| 10 | Remove the water pump. Refer to Water Pump Replacement . Inspect for a damaged water pump shaft/hub. Is the water pump driveshaft damaged or is the seal leaking? | Go to Step 8 | Go to Step 11 |
| 11 | Inspect for obstructed radiator air flow or bent radiator fins. Is the radiator air flow obstructed? | Go to Step 8 | Go to Step 12 |
| 12 | Inspect for blocked cooling system passages. Are the cooling system passages blocked? | Go to Step 8 | Go to Step 13 |
| 13 | Inspect for inoperative fan clutch. Is the fan clutch operating correctly? | Go to Step 14 | Go to Step 8 |
| 14 | Inspect the thermostat. Refer to Thermostat Diagnosis . Is the thermostat stuck in the closed position? | Go to Step 15 | Go to Step 16 |
| 15 | Replace the thermostat. Refer to Engine Coolant Thermostat Housing Replacement . Does the engine overheat? | Go to Step 16 | System OK |
| 16 | Inspect the radiator cooling capacity. Is the proper sized radiator being used on the vehicle? | Go to Step 3 | Go to Step 17 |
| 17 | Consult the current parts catalog and replace the radiator. Refer to Radiator Replacement (Electric) . Is the repair complete? | System OK |
Loss of Coolant
| Step | Action | Yes | No |
|---|---|---|---|
| DEFINITION: The cooling system is loosing coolant either internally or externally. | |||
| 1 | Were you sent here from Symptoms, or another diagnostic table? | Go to Step 2 | Go to Symptoms - Engine Cooling |
| 2 | Repair any present DTCs. Refer to Diagnostic System Check - Vehicle . Is the action complete? | Go to Step 3 | |
| 3 | Inspect the coolant level. Is the coolant at the proper level? | Go to Step 5 | Go to Step 4 |
| 4 | Fill the cooling system to the proper level. Refer to Cooling System Draining and Filling (Static Fill) or Cooling System Draining and Filling (Vac-N-Fill) . Is the action complete? | Go to Step 5 | |
| 5 | Engine overheating can cause a loss of coolant. Is the engine overheating? | Go to Step 19 | Go to Step 6 |
| 6 | Idle the engine at normal operating temperature. Inspect for heavy white smoke coming out of the exhaust pipe. Is a heavy white smoke present from the exhaust pipe? | Go to Step 7 | Go to Step 8 |
| 7 | Coolant in the exhaust system creates a distinctive, burning coolant odor in the exhaust. Condensation in the exhaust system can cause an odorless white smoke during engine warm up. Does the white smoke have a burning coolant type odor? | Go to Step 20 | Go to Step 8 |
| 8 | Visually inspect the hoses, pipes and hose clamps. Are any of the hoses, clamps or pipes leaking? | Go to Step 21 | Go to Step 9 |
| 9 | Visually inspect the following components: Block heater Coolant pressure cap Core plugs Throttle Body Engine block Intake manifold Radiator Thermostat housing Water pump Are any of the listed components leaking? | Go to Step 21 | Go to Step 10 |
| 10 | Pressure test the cooling system. Refer to Cooling System Leak Testing . With the cooling system pressurized, visually inspect the components listed in steps 7 and 8. Are any leaks present? | Go to Step 21 | Go to Step 11 |
| 11 | Pressure test the coolant pressure cap. Refer to Pressure Cap Testing . Does the coolant pressure cap hold pressure? | Go to Step 12 | Go to Step 16 |
| 12 | Inspect for the following conditions: A coolant smell inside of the vehicle Coolant in the HVAC module drain tube Coolant on the vehicle floor covering near the HVAC module Is coolant present? | Go to Step 21 | Go to Step 13 |
| 13 | Inspect the underside of the engine oil fill cap for a gray/white milky substance. Is there a milky substance under the oil fill cap? | Go to Step 14 | Go to Step 15 |
| 14 | Inspect the engine oil fluid level indicator for a gray/white milky substance. Is there a milky substance on the engine oil fluid level indicator? | Go to Step 17 | Go to Step 15 |
| 15 | Inspect the automatic transmission oil fluid level indicator, if equipped, for a gray/white milky substance. Is there a milky substance on the automatic transmission fluid level indicator? | Go to Step 18 | Go to Step 22 |
| 16 | Replace the coolant pressure cap. Is the repair complete? | Go to Step 22 | |
| 17 | Replace the radiator. Refer to Radiator Replacement (Electric) . Service the engine oil and filter. Refer to Engine Oil and Oil Filter Replacement . Is the repair complete? | Go to Step 22 | |
| 18 | Replace the radiator. Refer to Radiator Replacement (Electric) . Service the automatic transmission. Refer to Engine Coolant/Water in Transmission . Is the repair complete? | Go to Step 22 | |
| 19 | Repair the engine overheating condition. Refer to Engine Overheating . Is the repair complete? | Go to Step 22 | |
| 20 | Repair the engine internal coolant leak. Refer to Coolant in Combustion Chamber and Coolant in Engine Oil . Is the repair complete? | Go to Step 22 | |
| 21 | Repair or replace the leaking component. Refer to the appropriate repair. Is the repair complete? | Go to Step 22 | |
| 22 | Operate the system in order to verify the repair. Did you find and correct the condition? | System OK | Go to Step 2 |
Tools Required
J 24731 Tempil Stick. See Special Tools .
Use one of the following procedures in testing for a malfunctioning thermostat.
Engine Fails To Reach Normal Operating Temperature
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Did you review the Symptoms-Engine Cooling diagnostic information and perform the necessary inspections? | Go to Step 2 | Go to Symptoms - Engine Cooling |
| 2 | Verify that the engine does not reach normal operating temperature. Does the engine reach normal operating temperature? | System OK | Go to Step 3 |
| 3 | Inspect the coolant level. Is the coolant level below the add mark? | Go to Step 4 | Go to Step 5 |
| 4 | Add coolant as necessary. Perform a cooling system pressure test. Does the cooling system hold pressure? | System OK | Go to Step 5 |
| 5 | Inspect for a stuck open, missing, or incorrect thermostat. Refer to Thermostat Diagnosis . Is the thermostat operating properly? | System OK | Go to Step 6 |
| 6 | Install the correct replacement thermostat. Refer to Engine Coolant Thermostat Housing Replacement Is the repair complete? | Go to Step 7 | |
| 7 | Run the engine in order to verify the repair. Does the engine fail to reach normal operating temperature? | System OK |
- J 24460-01 Cooling System Pressure Tester. See «Special Tools»(ref-299178-S33492269542008092200000) .
- J 42401 Radiator Cap/Surge Tank Test Adapter. See «Special Tools»(ref-299178-S33492269542008092200000) .
Filling Procedure
- Install the lower radiator hose to the radiator.
- Using the J 38185 reposition the lower radiator hose clamp. See «Special Tools»(ref-299178-S33492269542008092200000) .
- If the left and right engine block coolant drain plugs were removed, perform the following. Apply pipe sealer to the drain plugs. NOTE: Refer to «Fastener Notice»(ref-299114-S36079355232008092200000) . Install the drain plugs. Tighten: Tighten the drain plugs to 60 N.m (44 lb ft).
- Install the engine block coolant heater, if equipped. Refer to «Coolant Heater Replacement»(ref-299178-S38155781592008092200000) .
- Lower the vehicle.
- Open the cooling system bleeder screws, if equipped.
- Slowly fill the cooling system with a 50/50 coolant mixture. Refer to «Approximate Fluid Capacities»(ref-299186-S38192096262008092200000) .
- Close the cooling system bleeder screws, if equipped.
- Install the coolant pressure cap.
- Start the engine.
- Run the engine at 2,000-2,500 RPM until the engine reaches normal operating temperature.
- Allow the engine to idle for 3 minutes.
- Shut the engine OFF.
- Allow the engine to cool.
- Top off the coolant as necessary.
- Inspect the concentration of the engine coolant using the J 26568 . See «Special Tools»(ref-299178-S33492269542008092200000) .
- Rinse away any excess coolant from the engine and the engine compartment.
Radiator Cleaning
| CAUTION | NEVER spray water on a hot radiator. The resulting steam could cause personal injury. |
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.
- Some conditions may require the use of warm water and a mild detergent.
- Clean the A/C condenser fins.
- Clean between the A/C condenser and radiator.
- Clean the radiator cooling fins.
- Straighten any damaged cooling fins.
J 43181 Heater Line Quick Connect Release Tool. See Special Tools .
Cooling Fan Control - Two Fan System
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 engine control module (ECM) to operate both fans together at low or high speeds. The cooling fans receive positive voltage from the cooling fan relays which receive battery positive voltage from the underhood fuse block. The fan relay coils receive ignition 1 voltage from the powertrain relay.
During low speed operation, the ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the low speed fan relay coil, closes the relay contacts, and supplies battery positive voltage from the low fan 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 series/parallel relay and the right cooling fan. The result is a series circuit with both fans running at low speed.
During high speed operation the ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. The ECM grounds the high speed fan relay and the cooling fan series/parallel relay through the high speed cooling fan relay control circuit. This energizes the cooling fan control relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the high speed fan relay coil is energized closing the relay contacts and provides battery positive voltage from the high fan 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.
Refer to Engine Cooling Schematics .
ENGINE COOLANT HOT
The instrument panel cluster (IPC) illuminates the ENGINE COOLANT HOT indicator in the message center when the IPC determines that the coolant temperature is greater than 121°C (251°F). The IPC receives a class 2 message from the powertrain control module (PCM) indicating the coolant temperature.
ENGINE OVERHEATED
The IPC illuminates the ENGINE OVERHEATED indicator in the message center when the IPC determines that the coolant temperature is greater than 128°C (262°F). The IPC receives a class 2 message from the PCM indicating the coolant temperature.
REDUCED ENGINE POWER
The IPC illuminates the REDUCED ENGINE POWER indicator in the message center when the IPC detects a reduced engine power condition from the PCM. The IPC receives a class 2 message from the PCM requesting illumination when the engine temperature reaches 128°C (262°F).
Coolant Heater
The optional engine coolant heater (RPO K05) operates using 110-volt 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.
Cooling System
The cooling system's 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 is drawn from the radiator outlet and into the water pump inlet by the water pump. Coolant will then be pumped through the water pump outlet and into the engine block. In the engine block, the coolant circulates through the water pump outlet and into the engine block. In the engine block, the coolant circulates through the water jackets surrounding the cylinders, where it absorbs heat.
Some coolant is also pumped from the water pump to the heater core, then back to the water pump. This provides the passenger compartment with heat and defrost.
The coolant is then forced 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 it absorbs additional heat.
Coolant is also directed to the throttle body. There it circulates through passages in the casting. During initial start up, the coolant assists in warming the throttle body. During normal operating temperatures, the coolant assists in regulating the throttle body temperature.
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. It consists of a core and two 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 removes heat from the coolant passing through it. The fins on the core transfer heat from the coolant passing through the tubes. As air passes between the fins, it absorbs heat and cools the coolant.
Surge Tank
The surge tank is a plastic tank with a threaded pressure cap. The tank is mounted at a point higher than all other coolant passages. The surge tank provides an air space in the cooling system that allows the coolant to expand and contract. The surge tank provides a coolant fill point and a central air bleed location.
During vehicle use, the coolant heats and expands. The increased coolant volume flows into the surge tank. As the coolant circulates, any air is allowed to bubble out. Coolant without air bubbles absorbs heat much better than coolant with bubbles.
Pressure Cap
The pressure cap seals the cooling system. It contains a blow off or pressure relief valve and a vacuum or atmospheric valve. The pressure valve is held against its seat by a spring, which protects the radiator from excessive cooling system pressure. The vacuum valve is held against its seat by a spring, which permits opening of the valve to relieve vacuum created in the cooling system as it cools off. The vacuum, if not relieved, might cause the radiator and/or coolant hoses to collapse.
The pressure cap allows cooling system pressure to build up as the temperature increases. As the pressure builds, the boiling point of the coolant increases. 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 is, the faster the heat transfers from the radiator to the cooler, passing air.
The pressure in the cooling system can get too high. When the cooling system pressure exceeds the rating of the pressure cap, it raises the pressure valve, venting the excess pressure.
As the engine cools down, the temperature of the coolant drops and a vacuum is created in the cooling system. This vacuum causes the vacuum valve to open, allowing outside air into the surge tank. This equalizes the pressure in the cooling system with atmospheric pressure, preventing the radiator and coolant hoses from collapsing.
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 mounted on the pump shaft and consists of a series of flat or curved blades or vanes on a flat plate. 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. The sealed bearings never need to be lubricated. Grease cannot leak out, dirt and water cannot get in as long as the seal is not damaged or worn.
The purpose of the water pump is to circulate coolant throughout the cooling system. The water pump is driven by the crankshaft via the drive belt.
Thermostat
The thermostat is a coolant flow control component. It's purpose is to help regulate the operating temperature of the engine. It utilizes a temperature sensitive wax-pellet element. The element connects to a valve through a small piston. When the element is heated, it expands and exerts pressure against the small piston. This pressure forces the valve to open. As the element is cooled, it contracts. This contraction allows a spring to push the valve closed.
When the coolant temperature is below the rated thermostat opening temperature, the thermostat valve remains closed. This prevents circulation of the coolant to the radiator and allows the engine to warm up. After the coolant temperature reaches the rated thermostat opening temperature, 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, after it has opened. 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. It is located inside the left side end tank of the radiator. The engine oil temperature is controlled by the temperature of the engine coolant that surrounds the oil cooler in the radiator.
The engine oil pump, pumps the oil through the engine oil cooler line to the oil cooler. The oil then flows through the cooler where the engine coolant absorbs heat from the oil. The oil is then pumped through the oil cooler return line, to the oil filter, to the engine block oil system.
Transmission Oil Cooler
The transmission oil cooler is a heat exchanger. It is located inside the right side end tank of the radiator. The transmission fluid temperature is regulated by the temperature of the engine coolant in the radiator.
The transmission oil pump, pumps the fluid through the transmission oil cooler line to the transmission oil cooler. The fluid then flows through the cooler where the engine coolant absorbs heat from the fluid. The fluid is then pumped through the transmission oil cooler return line, to the transmission.