Engine Cooling System: Diagnosis Pontiac Aztek I

Diagnostic Starting Point - Engine Cooling

Begin the system diagnosis with the DIAGNOSTIC SYSTEM CHECK - ENGINE COOLING . The Diagnostic System Check will provide the following information

1. The identification of the control module(s) which command the system.
2. The ability of the control module(s) 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 Data Definitions

Coolant Hot Lamp: The scan tool displays ON/OFF. The scan tool displays ON when the engine coolant temperature is above 120°C (248°F).

Coolant Temperature: The scan tool displays -40 to +151°C (-40 to +304°F). This data is the coolant temperature the Instrument Cluster is attempting to display on the coolant temperature gauge.

ECT: The scan tool displays -40 to +151°C (-40 to +304°F). The Engine Coolant Temperature (ECT) sensor is mounted in the coolant stream. The PCM applies 5 volts to the ECT sensor circuit. The sensor is a thermistor which changes internal resistance as temperature changes. When the sensor is cold (internal resistance high), the PCM monitors a high signal voltage and interprets it as a cold engine. As the sensor warms (internal resistance decreases), the voltage signal decreases and the PCM interprets the lower voltage as a warm engine.

FC Relay 1: The scan tool displays OK or Fault. This parameter indicates the state of the driver circuit for this device.

FC Relay 2 and 3: The scan tool displays OK or Fault. This parameter indicates the state of the driver circuit for this device.

Fans High Speed: The scan tool displays On or Off. The PCM is commanding all three fan control relays on when the scan tool indicates On. When all fan control relays are activated, both cooling fans are enabled on high speed.

Fans Low Speed: The scan tool displays On or Off. The PCM is commanding Fan Control relay 1 On when the scan tool indicates On. When the PCM commands the Fan Control relay 1 On, both fans are enabled on low speed.

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Circuit Description

1. P0480 is for the low speed cooling fan relay control circuit.
2. P0481 is for the high speed cooling fan relay control circuit.

Battery positive voltage is supplied to the cooling fan 1 relay from the COOL FAN #1 fuse. The powertrain control module (PCM) controls the cooling fan 1 relay by grounding the low speed cooling fan relay control circuit via an internal solid state device called a driver.

Battery positive voltage is supplied to the cooling fan 2 relay and the cooling fan 3 relay from the COOL FAN #2 fuse. The powertrain control module (PCM) controls the relays by grounding the high speed cooling fan relay control circuit.

When the PCM is commanding a relay on, the voltage potential of the control circuit should be low, near 0 volts. When the PCM is commanding the control circuit to a relay, the voltage potential of the circuit should be high, near battery voltage. If the fault detection circuit senses a voltage other than what is expected, the DTC will set.

The PCM will monitor the control circuit for the following

1. A short to ground
2. A short to voltage
3. An open circuit
4. An open relay coil
5. An internally shorted or excessively low resistance relay coil

When the PCM detects any of the above conditions, the DTC will set and the affected driver will be disabled.

Conditions for Running the DTC

1. The ignition is ON.
2. System voltage is between 9-18 volts.
3. The relay control circuit is transitioned from OFF to ON or ON to OFF.

Conditions for Setting the DTC

1. The PCM detects an open, a short to ground or a short to voltage on the cooling fan relay control circuit.
2. The above conditions are present for at least 30 seconds.

Action Taken When the DTC Sets

1. The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed.
2. The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data.

Conditions for Clearing the MIL/DTC

1. The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed.
2. The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
3. The DTC can be cleared by using the scan tool.

Diagnostic Aids

1. If the condition is not present, refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS in Wiring Systems.
2. Review the Freeze/Failure Records vehicle mileage since the diagnostic test last failed. This may help determine how often the condition that caused the DTC to be set occurs.

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the Cooling System. Refer to CHECKING AFTERMARKET ACCESSORIES in Wiring Systems.
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
3. Inspect the surge tank reservoir for the proper coolant level.

Symptom List

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

1. Engine Coolant Temperature Indicator Always On, See «Engine Coolant Temperature Indicator Always On Table»(ref-203946-S03914948062005091900000)
2. Cooling Fan Always On, See «Cooling Fan Always On Table»(ref-203946-S08639237952005091900000)
3. Cooling Fan Inoperative, See «Cooling Fan Inoperative Table»(ref-203946-S15260983522005091900000)
4. Coolant Heater Inoperative, See «Coolant Heater Inoperative»(ref-203946-S14458170432005091900000)
5. Engine Overheating, See «Engine Overheating Table»(ref-203946-S25071562202005091900000)
6. Loss Of Coolant, See «Loss of Coolant Table»(ref-203946-S28434031352005091900000)
7. «Thermostat Diagnosis»(ref-203946-S19387838612005072900000)
8. Engine Fails To Reach Normal Operating Temperature, See «Engine Fails To Reach Normal Operating Temperature»(ref-203946-S40253571472005091900000)

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Thermostat Test Procedure Using Tempil Sticks

The coolant thermostat can be tested using a temperature (tempil) stick. The temperature stick is a pencil like device. It has a wax material containing certain chemicals which melt at a given temperature.

Temperature sticks can be used to determine a thermostat's operating range, by rubbing 87°C (188°F) and 97°C (206°F) sticks on the thermostat housing.

1. Use a tempil stick in order to find the opening and the closing temperatures of the coolant thermostat. J 24731-188 tempil stick melts at 87°C (188°F). The thermostat should begin to open. J 24731-206 tempil stick melts at 97°C (206°F). The thermostat should be fully open.
2. Replace the coolant thermostat if it does not operate properly between this temperature range.

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