Engine Cooling System: Diagnosis Chevrolet Aveo I facelift

DIAGNOSTIC CODE INDEX

DIAGNOSTIC CODE INDEX

Diagnostic Starting Point - Engine Cooling

Begin diagnosis with the Diagnostic System Check - Vehicle . The Diagnostic System Check will provide the following information

1. The identification of the control modules which command the system
2. The ability of the control modules to communicate through the serial data circuit
3. The identification of any stored diagnostic trouble codes (DTCs) and their status

The use of the Diagnostic System Check will identify the correct procedure for diagnosing the system and where the procedure is located.

Scan Tool Output Controls

Scan Tool Data List

The Engine Scan Tool Data List contains all engine related parameters that are available on the scan tool. The list is arranged in alphabetical order. A parameter may appear in any one of the data lists, and in some cases may appear more than once, or in more than one data list in order to group certain related parameters together.

Use the Engine Scan Tool Data List only after the following conditions are determined

1. The Diagnostic System Check - Engine Controls is completed.
2. There are no DTCs.
3. The on-board diagnostics are functioning correctly.

Scan tool values from an engine that is operating correctly may be used for comparison with the engine you are diagnosing. The Engine Scan Tool Data List represents the values that would be seen on a normal operating engine.

Only the parameters listed below are referenced in this service information for use in diagnosis.

The column labeled Data List indicates where a parameter is located on the scan tool. Review the scan tool operating manual for the exact locations of the data lists. The following is a description of each term listed

Scan Tool Data Definitions

The Scan Tool Data Definitions list contains a brief description of all of the engine related parameters that are available on the scan tool. The list is arranged in alphabetical order. A given parameter may appear in any one of the data lists. In some cases the parameter may appear more than once, or in more than one data list in order to group certain related parameters together.

Circuit Description

The Cooling Fan Relay 1 and the Cooling Fan Relay 2 are controlled by the engine control module (ECM). Battery positive voltage is supplied to the relay coil. The ECM monitors the voltage level on the control circuit of the relay. When the relay is OFF, voltage level should be near battery voltage on the control circuit of the relay. When the relay is commanded ON, voltage level will be low on the control circuit of the relay. The ECM will provide ground on the control circuit of the relay using a low side driver. If the ECM detects a improper voltage level on the control circuit of the relay, a DTC will set.

DTC Descriptors

This diagnostic procedure supports the following DTCs

1. DTC P0480 Cooling Fan Relay 1 Control Circuit
2. DTC P0481 Cooling Fan Relay 2 Control Circuit

Conditions for Running the DTC

1. The ignition is ON or the engine is operating.
2. The ignition 1 voltage is more than 10 volts.
3. DTCs P0480 and P0481 run continuously once the above conditions are met.

Conditions for Setting the DTC

The ECM detects one of the following conditions on the control circuit of one of the relays

1. An open
2. A short to ground
3. A short to voltage

Action Taken When the DTC Sets

1. The malfunction indicator lamp (MIL) will not illuminate.
2. The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.

Conditions for Clearing the MIL/DTC

1. DTCs can be cleared by using the scan tool.
2. Disconnect the ECM battery feed for more than 10 seconds.

Diagnostic Aids

1. For an intermittent condition, refer to «Testing for Intermittent Conditions and Poor Connections»(ref-300844-S37738883112008101600000) .
2. The following tables illustrate the COOL FAN LOW relay and COOL FAN HIGH relay terminal locations in the underhood fuse block

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the system.
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. «Cooling Fan Circuit Diagnosis (Dual Fans)»(ref-300853-S07596369092008101600000) or «Cooling Fan Circuit Diagnosis (Single Fan)»(ref-300853-S10326282952008101600000)
2. «Engine Overheating»(ref-300853-S34527350262008101600000)
3. «Loss of Coolant»(ref-300853-S40169521502008101600000)
4. «Thermostat Diagnosis»(ref-300853-S20666437632008101600000)
5. «Coolant Heater Inoperative»(ref-300853-S26666569982008101600000)
6. «Engine Fails To Reach Normal Operating Temperature»(ref-300853-S05106325882008101600000)

The engine cooling fan circuit operates the main cooling fan and the auxiliary cooling fan. The cooling fans are controlled by the engine control module (ECM) based on inputs from the engine coolant temperature (ECT) sensor and the air conditioning pressure (ACP) sensor. The ECM controls the low speed cooling fan operation by providing a ground signal to the low speed fan relay. This energizes the low speed cooling fan relay and operates the main cooling fan and the auxiliary cooling fan at low speed as the cooling fans are connected in a series circuit. The ECM controls the high speed cooling fan operation by providing a ground signal to the high speed cooling fan relay and the series/parallel relay a the same time. This energizes the low speed cooling fan relay, the high speed cooling fan relay, and the series/parallel cooling fan relay resulting in high speed fan operation as the cooling fans are now connected in a parallel circuit.

1. If the owner complained of an overheating problem, it must be determined if the complaint was due to an actual boil over, or the engine coolant temperature gage indicated overheating. If the engine is overheating and the cooling fans are ON, the cooling system should be inspected.
2. If the engine fuse block fuses EF3 become open, blown, immediately after installation, inspect for a short to ground in the wiring of the appropriate circuit. If the fuses become open, blown, when the cooling fans are to be turned ON by the ECM, suspect a faulty cooling fan motor.
3. The ECM will turn the cooling fans ON at low speed when the coolant temperature is 97°C (207°F). The ECM will turn the cooling fans OFF when the coolant temperature is 94°C (201°F).
4. The ECM will turn the cooling fans ON at high speed when the coolant temperature is 101°C (214°F). The ECM will change the cooling fans from high speed to low speed when the coolant temperature is 98°C (208°F).
5. The ECM will turn the cooling fans ON at low speed when the A/C system is ON. The ECM will change the cooling fans from low speed to high speed when the high side A/C pressure is 1882 kPa (273 psi), then return to low speed when the high side A/C pressure is 1448 kPa (210 psi). When the A/C system is ON, the ECM will change the cooling fans from low to high speed when the coolant temperature reaches 117°C (244°F), then return to low speed when the coolant temperature reaches 114°C (237°F).
6. The cooling fan circuit can be inspected quickly by disconnecting the ECM and ground the low speed relay control circuit. This should create low speed cooling fan operation with the ignition ON. By grounding the ECM low speed relay control circuit and the high speed relay control circuit and turning the ignition ON, high speed cooling fan operation should be achieved.

The engine cooling fan circuit operates the cooling fan. The cooling fan is controlled by engine control module (ECM) based on input from the engine coolant temperature (ECT) sensor. The ECM controls the low speed cooling fan operation by providing a ground signal to the low speed fan relay. This energizes the low speed cooling fan relay and operates the cooling fan at low speed. The low speed cooling fan operation is achieved by the cooling fan resistor causing a drop in the voltage supplied to the cooling fan. The ECM controls the high speed cooling fan operation by providing a ground signal to the high speed fan relay. This energizes the high speed cooling fan relay, bypassing the radiator fan resistor. This results in high speed cooling fan operation.

1. If the owner complained of an overheating problem, it must be determined if the complaint was due to an actual boil over, or the engine coolant temperature gage indicated overheating. If the engine is overheating and the cooling fans are ON, the cooling system should be inspected.
2. If the I/P fuse block fuse F18 or the engine fuse block fuse EF3 or main relay fuse EF2 (1.2L only), become open, blown, immediately after installation, inspect for a short to ground in the wiring of the appropriate circuit. If the fuses become open, blown, when the cooling fan is to be turned ON by the ECM, suspect a faulty cooling fan motor.
3. The ECM will turn the cooling fans ON at low speed when the coolant temperature is 93°C (199°F). The ECM will turn the cooling fans OFF when the coolant temperature is 90°C (194°F).
4. The ECM will turn the cooling fans ON at high speed when the coolant temperature is 97°C (207°F). The ECM will change the cooling fans from high speed to low speed when the coolant temperature is 94°C (201°F).
5. The cooling fan circuit can be inspected quickly by disconnecting the ECM connector and grounding the low cooling fan control circuit. This should create low speed cooling fan operation with the ignition ON. By grounding the ECM low cooling fan relay and high cooling fan relay control circuits and turning the ignition ON, high speed cooling fan operation should be achieved.

Thermostat Diagnosis

Testing

The surge tank cap maintains proper pressure, protects the system from high pressure by opening a pressure valve, and protects the coolant hoses from collapsing because of a vacuum.

1. Wash any sludge from the surge tank cap and the valve seat of the vacuum pressure valve for the surge tank cap.
2. Check for any damage or deformity to the vacuum pressure valve for the surge tank cap. If any damage or deformity is found, replace the cap.
3. Install a suitable cooling system pressure tester to the cap using the J-36649 . See «Special Tools»(ref-300853-S36492369312008101600000) .
4. Pull the vacuum pressure valve open. If the surge tank cap does not seal properly, replace the surge tank cap.
5. Pressurize the cap to 120-160 kPa (17-23 psi).
6. Wait 10 seconds and check the pressure held by the tank cap tester.
7. If the pressure held by the cooling system pressure tester falls below 80 kPa (16 psi), replace the surge tank cap.

Coolant Pump Cleaning and Inspection

1. Inspect the coolant pump body for cracks and leaks.
2. Inspect the coolant pump bearing for play or abnormal noise.
3. Inspect the coolant pump pulley for excessive wear. If the coolant pump is defective, replace the coolant pump as a unit.
4. Clean the mating surfaces of the coolant pump and cylinder block.