Engine Cooling System: Other GMC Sierra III

Reference Information

Schematic Reference

Engine Heating/Cooling Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Cooling Fan Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-651023-S06735791342014081900000)
2. «Connector Repairs»(ref-651023-S36930316752014081900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-651023-S31795657182014081900000)
4. «Wiring Repairs»(ref-651023-S35699655412014081900000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

K20 Engine Control Module: Scan Tool Information (LV3, L83 or L86) for scan tool information

Circuit/System Verification

1. Engine operating, command the Cooling Fans from 0 % to 90 % with a scan tool.
2. Verify the G10 Cooling Fan Motors activates in each available speed. The cooling fan does not activate or increase in speed as commanded Refer to Circuit/System Testing The cooling fan activates and increases in speed as commanded
3. 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.
4. Verify the DTC does not set. If the DTC sets Refer to Circuit/System Testing If the DTC does not set
5. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Engine Coolant Fan Replacement (L83, LV3)»(ref-651030-S04286758742014081900000) for G10 Cooling Fan Motor Replacement.
2. «Control Module References»(ref-651024-S37773196412014081900000) for ECM replacement, setup and programming

Schematic Reference

Engine Controls Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

1. «Cooling Fan Description and Operation»(ref-651030-S07264127982014081900000)
2. «Instrument Cluster Description and Operation»(ref-651017-S37454875942014081900000)
3. «Indicator/Warning Message Description and Operation»(ref-651017-S36116498242014081900000)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

K20 Engine Control Module: Scan Tool Information (LV3, L83 or L86) for scan tool information

1. Ignition ON.
2. Verify DTC P0480, P0691 or P0692, is not set. If a DTC is set Refer to «DTC P0480, P0691 or P0692»(ref-651030-S09494553142014081900000) . If no DTCs is set
3. Verify the cooling fan operates at each available speed as commanded with a scan tool. Cooling fan does not operate Refer to «Cooling Fan Inoperative»(ref-651030-S06286087172014081900000) . Cooling fan operates
4. Verify that the engine does not overheat. Engine overheats Refer to «Engine Overheating»(ref-651030-S32653475622014081900000) . Engine does not overheat
5. Operate the vehicle within the Conditions for Running the DTC. If the DTC sets Refer to «Symptoms - Engine Cooling»(ref-651030-S24280215982014081900000) . If the DTC does not set
6. All OK

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.

Schematic Reference

Engine Heating/Cooling Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Cooling Fan Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-651023-S06735791342014081900000)
2. «Connector Repairs»(ref-651023-S36930316752014081900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-651023-S31795657182014081900000)
4. «Wiring Repairs»(ref-651023-S35699655412014081900000)

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON.
2. Verify that DTC P0480, P0691 or P0692, is not set. If a DTC is set Refer to «DTC P0480, P0691 or P0692»(ref-651030-S09494553142014081900000) . If no DTC is set.
3. Verify the scan tool Cooling Fan Motor Command parameter is 0 %. If greater than 0 % Refer to Diagnostic Aids and «Symptoms - Engine Cooling»(ref-651030-S24280215982014081900000) for further diagnosis. If 0 %
4. Verify that the G10 Cooling Fan Motors are not operating. If a G10 Cooling Fan Motor is operating Test or replace the appropriate G10 Cooling Fan Motor. If the G10 Cooling Fan Motor is not operating
5. All OK.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Engine Coolant Fan Replacement (L83, LV3)»(ref-651030-S04286758742014081900000) for G10 Cooling Fan Motor Replacement.
2. «Control Module References»(ref-651024-S37773196412014081900000)

Schematic Reference

Engine Heating/Cooling Schematics

Connector End View Reference

COMPONENT CONNECTOR END VIEWS - INDEX

Description and Operation

Cooling Fan Description and Operation

Electrical Information Reference

1. «Circuit Testing»(ref-651023-S06735791342014081900000)
2. «Connector Repairs»(ref-651023-S36930316752014081900000)
3. «Testing for Intermittent Conditions and Poor Connections»(ref-651023-S31795657182014081900000)
4. «Wiring Repairs»(ref-651023-S35699655412014081900000)

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON.
2. Verify that DTC P0480, P0691 or P0692, is not set. If a DTC is set Refer to «DTC P0480, P0691 or P0692»(ref-651030-S09494553142014081900000) . If no DTC is set.
3. Verify the G10 Cooling Fan Motor activates and increases in speed with each command using a scan tool. The cooling fan does not activate or increase in speed Refer to Circuit/System Testing The cooling fan activates and increases in speed
4. All OK.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Engine Coolant Fan Replacement (L83, LV3)»(ref-651030-S04286758742014081900000) for G10 Cooling Fan Motor replacement.
2. «Control Module References»(ref-651024-S37773196412014081900000)

Engine Overheating

Engine Overheating

Loss of Coolant (L83)

Loss of Coolant (L83)

Loss of Coolant (LV3)

Loss of Coolant (LV3)

Electrical Information Reference

1. «Circuit Testing»(ref-651023-S06735791342014081900000)
2. «Connector Repairs»(ref-651023-S36930316752014081900000)
3. «Wiring Repairs»(ref-651023-S35699655412014081900000)

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Coolant Heater Replacement (L83)»(ref-651030-S28586965222014081900000) , «Coolant Heater Replacement (LV3)»(ref-651030-S24964864112014081900000)
2. «Coolant Heater Cord Replacement»(ref-651030-S37087655902014081900000)

Engine Fails To Reach Normal Operating Temperature

Engine Fails To Reach Normal Operating Temperature

Filling Procedure

1. Install the lower radiator hose and/or drain cock to the radiator.
2. Using the J 38185 hose clamp pliers, reposition the lower radiator hose clamp.
3. If the left and right engine block coolant drain plugs were removed, perform the following: Apply pipe sealer to the drain plugs. Install the drain plugs. Tighten Tighten the drain plugs to 60 (44 lb ft).
4. Install the engine block coolant heater, if equipped. Refer to «Coolant Heater Replacement (L83)»(ref-651030-S28586965222014081900000) , «Coolant Heater Replacement (LV3)»(ref-651030-S24964864112014081900000) .
5. Lower the vehicle.
6. Slowly fill the cooling system with a 50/50 coolant mixture. Refer to «Approximate Fluid Capacities»(ref-650996-S03129344952014081900000) .
7. Install the coolant pressure cap.
8. Start the engine.
9. Run the engine at 2, 000-2, 500 RPM until the engine reaches normal operating temperature. Engine should reach an operating temperature of 90°C (194°F) and the upper radiator hose should be HOT.
10. Allow the engine to idle for 3 minutes.
11. Shut the engine OFF.
12. Allow the engine to cool.
13. Top off the coolant as necessary.
14. Inspect the concentration of the engine coolant using the J 26568 coolant and battery tester.
15. Rinse away any excess coolant from the engine and the engine compartment.

Radiator Cleaning

1. Some conditions may require the use of warm water and a mild (non caustic) 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 31

Radiator Surge Tank Replacement (L83)

Cooling Fan Control

The engine cooling fan system is composed of 2 electric cooling fans, fan motors and 2 control modules. The engine control module (ECM) controls the fan speed by sending a pulse width modulated (PWM) signal to the cooling fan control modules. The cooling fan control module varies the voltage drop across the cooling fan motors in relation to the pulse width modulated signal, which allows the cooling fans to operate at variable speeds.

The cooling fan speed is effected by many different conditions and the ECM will adjust the duty cycle from 0-100 percent based on cooling system requirements. The scan tool output control is only capable of operating the cooling fan increments, between 10-90 percent. 90 percent is considered high speed fan. When multiple cooling fan speed requests are received, the ECM operates the fan at the highest of speed requests. The ECM commands the fans ON under the following conditions

1. The engine coolant temperature is warmer than a predetermined temperature.
2. The engine oil temperature is warmer than a predetermined temperature.
3. The A/C pressure reaches a predetermined pressure.
4. If the engine coolant temperature at key-off is warmer than a predetermined value or the A/C pressure is greater than a predetermined value, the cooling fan will operate at a low speed. The fan will shut OFF if the temperature or pressure drops below the predetermined value, but will only operate for 2 minutes, regardless of the coolant temperature or A/C pressure.

Engine Coolant Indicators

ENGINE COOLANT HOT

The instrument panel cluster (IPC) displays ENGINE COOLANT HOT message when the IPC receives a message from the powertrain control module (PCM) requesting illumination of this driver warning.

ENGINE OVERHEATED

The IPC displays ENGINE OVERHEATED message when the IPC receives a message from the PCM requesting illumination of this driver warning.

REDUCED ENGINE POWER

The IPC displays REDUCED ENGINE POWER message when the IPC detects a reduced engine power condition from the PCM. The IPC receives a message from the PCM requesting illumination when the engine temperature exceeds a calibrated value.

Coolant Heater (If Equipped)

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 -18°C (0°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 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 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 also has a drain cock (except HD), located in the bottom of the right hand tank. The drain cock unit includes the drain cock and drain cock seal.

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.

During vehicle use, the coolant heats and expands. The increased coolant volume can in some conditions push past the pressure cap and through a channel into the overflow bottle. As the coolant circulates, air is allowed to bubble out. This air is then transferred to the overflow bottle, through the surge tank cap, where it returns to the atmosphere. Coolant without air bubbles absorbs heat much better than coolant with bubbles. When the engine cools, the coolant, without air bubbles, contracts back into the surge tank from the bottom of the overflow bottle.

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.

Cooling Fan and Clutch

The engine cooling fan and clutch are driven by the crankshaft via the drive belt. The cooling fan draws air through the radiator to improve the transfer of heat from the coolant to the atmosphere. As the fan blades spin, they pull cool, outside air past the radiator core. The fan clutch drives the cooling fan. The fan clutch controls the amount of torque that is transmitted from the crankshaft to the fan blades. The clutch allows more torque to engage on the fan when the engine operating temperature increases and/or the vehicle speed is low. As the torque increases, the fan turns more quickly. The fan clutch decreases the torque applied to the cooling fan when the engine temperature decreases and/or the vehicle speed is high. As the torque decreases, the fan speed decreases.

Transmission Oil Cooler

The transmission oil cooler is a heat exchanger. It is located inside the right side (V6) or left side (V8), end tank of the radiator. The transmission fluid temperature is regulated by the temperature of the engine coolant that surrounds the oil cooler as the transmission fluid passes through the cooler.

The transmission oil pump, pumps the fluid through the transmission oil cooler feed line to the oil cooler. The fluid then flows through the cooler while the engine coolant absorbs heat from the fluid. The fluid is then pumped through the transmission oil cooler return line, to the transmission.

Engine Oil Cooler

The engine oil cooler is a heat exchanger located inside the left side (V6) or right side (V8), 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 engine block system.

Cooling Fan Control - Two Fan System

The engine cooling fan system consists of 2 electrical cooling fans, with a microcontroller that receives and allows the powertrain control module (PCM) to operate both fans together at several speeds. The cooling fans and fan PWM Signal receive battery positive voltage from the underhood fuse block.

During closed loop mode (PWM signal between 10% and 87%), both cooling fans will run at a controlled speed, depending on the percentage of PWM signal is being sent. At this closed loop mode, both fans will run at the speed it is being indicated according to the signal is being read by the microcontroller.

During open loop mode (PWM signal between 88% and 95%), both cooling fans will run at a non-controlled speed, this mode is when the fans will run at the maximum speed giving the maximum airflow, this mode is activated when conditions being mentioned later in this document activate it.

Note. The right and left cooling fan connectors are interchangeable. When servicing the fans be sure that the connectors are plugged into the correct fan.

The PCM commands the low speed cooling fans ON under the following conditions

1. Engine coolant temperature exceeds a calibrated value.
2. A/C refrigerant pressure exceeds a calibrated value.
3. After the vehicle is shut OFF if the engine coolant temperature at key-off is: 109°C-112°C then enable low speed fans. 107°C then disable low speed fans. 112°C then enable high speed fan. 105°C then disable high speed fans. The fans (high and low speed) will turn off after a maximum 5 min.

The PCM commands the high speed fans ON under the following conditions

1. Engine coolant temperature exceeds a calibrated value.
2. A/C refrigerant pressure exceeds a calibrated value.
3. When certain DTCs set.

At idle and very low vehicle speeds the cooling fans are only allowed to increase in speed if required. This insures idle stability by preventing the fans from cycling between high and low speed.