Engine Cooling System: Diagnosis Chevrolet Volt I

Diagnostic Code Index

DIAGNOSTIC CODE INDEX

Diagnostic Instructions

1. Perform the «Diagnostic System Check - Vehicle»(ref-487438-S13406627192012072300000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-487438-S08433352102012072300000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-487438-S20414004952012072300000) provides an overview of each diagnostic category.

Diagnostic Fault Information

Typical Scan Tool Data

Radiator Coolant Temperature Sensor

Conditions for Running the DTC

P00B3

1. The engine run time is greater than 10 seconds.
2. The intake air temperature (IAT) is colder than 70°C (158°F).
3. The DTC runs continuously when the above conditions are met.

P00B4

1. The engine run time is greater than 60 seconds.
2. The intake air temperature (IAT) is warmer than -7°C (19°F).
3. The DTC runs continuously when the above conditions are met.

Conditions for Setting the DTC

P00B3

The ECM detects that the RCT sensor is warmer than 149°C (300°F) for greater than 10 seconds.

P00B4

Note. The scan tool only displays to -40°C (-40°F).

The ECM detects that the RCT sensor is colder than -60°C (-76°F) for greater than 10 seconds.

Action Taken When the DTC Sets

DTC P00B3 and P00B4 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTC P00B3 and P00B4 are Type B DTCs.

Diagnostic Aids

1. As the thermostat opens, the RCT sensor temperature should rise steadily, then stabilize once the thermostat opens completely.
2. Test the RCT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor.
3. If the vehicle has sat for greater than 8 hours, the RCT sensor and the ECT sensor values should display within 3°C (5°F).

Circuit/System Testing

1. Vehicle OFF, disconnect the harness connector at the B203 engine coolant temperature sensor.
2. Vehicle OFF, all systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 5 ohms between the low reference circuit terminal 1 and ground. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20 ECM.
3. Vehicle in Service Mode, verify the scan tool Radiator Coolant Temperature Sensor parameter is at -40°C (-40°F). If warmer than the specified range, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the K20 ECM.
4. Install a 1 A fused jumper wire between the signal circuit terminal 2 and the low reference circuit terminal 1. Verify the Radiator Coolant Temperature Sensor parameter is at 140°C (284°F). If less than the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 ECM.
5. If all circuits test normal, test or replace the B203 engine coolant temperature sensor.

Component Testing

1. Vehicle OFF, remove the B203 engine coolant temperature sensor.
2. Test the engine coolant temperature sensor by varying the sensor temperature while monitoring the sensor resistance. Compare the readings with the «Temperature Versus Resistance»(ref-487511-S02115377072012072300000) table and verify that the resistance is within 5 percent of the specification. If not within the specified range, replace the B203 engine coolant temperature sensor.

1. Perform the «Diagnostic System Check - Vehicle»(ref-487438-S13406627192012072300000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-487438-S08433352102012072300000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-487438-S20414004952012072300000) provides an overview of each diagnostic category.

Radiator Coolant Temperature Sensor

Circuit Description

The engine coolant temperature sensor is a variable resistor that measures the temperature of the engine coolant in the radiator. The engine control module (ECM) supplies 5 volts to the engine coolant temperature signal circuit and supplies a ground to the low reference circuit. The purpose of this diagnostic is to determine if the input from the RCT sensor is skewed warmer than normal. The internal clock of the ECM will record the amount of time the engine is OFF. If the required engine OFF time is met at start-up, the ECM will compare the temperature difference between the actual measured RCT and ECT sensors.

The following table illustrates the difference between temperature, resistance, and voltage

1. DTCs P00B3, P00B4, P0112, P0113, P0116, P0117, P0118, P0502, P0503 or P2610 are not set.
2. The vehicle has been OFF and the propulsion system inactive for greater than 8 hours before vehicle ON.
3. The vehicle is ON, or the engine is running.
4. The intake air temperature (IAT) is warmer than -7°C (19°F).
5. The fuel level is greater than 10 percent.
6. The DTC runs once per ignition cycle when the above conditions are met.

The ECM determines the absolute difference of temperature between the RCT start up temperature and ECT start up temperature is greater than 20°C (68°F).

DTC P00B6 is a Type B DTC.

DTC P00B6 is a Type B DTC.

1. As the thermostat opens, the radiator coolant temperature sensor signal should rise steadily, then stabilize once the thermostat opens completely.
2. Inspect for the correct operation of the engine cooling system and verify the correct coolant level.

1. Vehicle OFF, disconnect the harness connector at the B203 engine coolant temperature sensor.
2. Vehicle OFF, all systems OFF. This may take up to 2 minutes for all vehicle systems to power down. Test for less than 5 ohms between the low reference circuit terminal 1 and ground. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20 ECM.
3. Vehicle in Service Mode, verify the scan tool Radiator Coolant Temperature Sensor parameter is at -40°C (-40°F). If warmer than the specified range, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the K20 ECM.
4. Install a 1 A fused jumper wire between the signal circuit terminal 2 and the low reference circuit terminal 1. Verify the scan tool Radiator Coolant Temperature Sensor parameter is at 140°C (284°F). If less than specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 ECM.
5. If all circuits test normal, test or replace the B203 ECT sensor.

1. Vehicle OFF, remove the B203 ECT sensor.
2. Test the engine coolant temperature sensor by varying the sensor temperature while monitoring the sensor resistance. Compare the readings with the «Temperature Versus Resistance»(ref-487511-S02115377072012072300000) table and verify that the resistance is within 5 percent of the specification. If not within the specified range, replace the B203 ECT sensor.

1. Perform the «Diagnostic System Check - Vehicle»(ref-487438-S13406627192012072300000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-487438-S08433352102012072300000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-487438-S20414004952012072300000) provides an overview of each diagnostic category.

Radiator Coolant Temperature Sensor

The engine control module (ECM) monitors the temperature of the engine radiator coolant. The ECM controls the thermostat with a pulse width modulated (PWM) signal. The ECM compares the radiator coolant temperature to the engine coolant temperature in order to determine if there sufficient coolant flow through the thermostat.

1. DTCs P00B3, P00B4, P00B6, P0116, P0117, and P0118 are not set.
2. The engine run time is greater than 45 s. OR
3. The engine coolant temperature is greater than 70°C (158°F).
4. The DTC runs continuously when the above conditions are met.

Note. The scan tool display range is between -40 and + 150°C (-40 and +302°F).

The ECM detects the difference between the RCT sensor and the ECT sensor is greater than 45°C (81°F) when the ECT sensor is warmer than 117°C (242°F) for greater than 5 s.

DTC P00B7 is a Type B DTC.

DTC P00B7 is a Type B DTC.

1. The thermostat has a mechanical fail-safe in case of an electrical condition with the thermostat heater. The mechanical thermostat will open at approximately 80°C (176°F). The mechanical thermostat will cycle from approximately 85°C (185°F) to approximately 102°C (215°F).
2. A resistance condition in the RCT sensor circuits may cause this DTC. This condition results in a greater voltage on the RCT sensor signal circuit, which is interpreted by the ECM as a colder RCT.

1. Vehicle OFF, inspect the cooling system for the conditions below. Refer to «Symptoms - Engine Cooling»(ref-487508-S14111027462012072300000) . Weak coolant solution Obstructed radiator air flow or bent radiator fins Blocked cooling system passages Radiator hoses that are restricted, collapsed, or deteriorated Damaged water pump and or belt Loss of cooling system pressure Leaking surge tank cap Radiator hoses Cylinder head or an engine block that is cracked or plugged If you find any of the above conditions, repair as necessary.
2. If all conditions test normal, replace the E41 engine coolant thermostat heater.

1. Perform the «Diagnostic System Check - Vehicle»(ref-487438-S13406627192012072300000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-487438-S08433352102012072300000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-487438-S20414004952012072300000) provides an overview of each diagnostic category.

Conditions for Running the DTCs

1. The ignition is ON, or the engine is running.
2. The DTCs run continuously once the above condition is met

The ECM detects that the commanded state of the driver and the actual state of the control circuit do not match for greater than 15 seconds.

1. DTCs P0597, P0598, and P0599 are Type B DTCs.
2. The engine control module commands the engine cooling fans ON.

Conditions for Clearing the DTC

DTCs P0597, P0598, and P0599 are Type B DTCs.

The thermostat has a mechanical fail-safe in case of an electrical condition with the thermostat heater. The mechanical thermostat will open at approximately 80°C (176°F). The mechanical thermostat will cycle from approximately 85°C (185°F) to approximately 102°C (215°F).

1. Vehicle OFF, disconnect the harness connector at the E41 engine coolant thermostat heater.
2. Vehicle in Service Mode, verify that a test lamp illuminates between the ignition circuit terminal 1 and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test all the components connected to the ignition circuit and replace as necessary.
3. Command the Engine Coolant Thermostat Heater to 10 % with a scan tool. Test for 2.5-3.5 V between the control circuit terminal 2 and ground. If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If the circuit/connections test normal, replace the K20 Engine Control Module. If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.
4. Command the Engine Coolant Thermostat Heater to 100 % with a scan tool. The DMM should transition from 2.5-3.5 V when commanded to 10 % to less than 0.1 V when commanded to 100 %. If the circuit voltage does not correspond to the specified values, replace the K20 Engine Control Module.
5. If all circuits test normal, test or replace the E41 engine coolant thermostat heater.

1. Perform the «Diagnostic System Check - Vehicle»(ref-487438-S13406627192012072300000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-487438-S08433352102012072300000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-487438-S20414004952012072300000) provides an overview of each diagnostic category.

1. DTC P2537 is not set.
2. The 12 V battery voltage is equal to or greater than 11 V.
3. The accessory circuit is active for greater than 5 seconds.
4. DTCs P1485, P1486, and P1487 run continuously when the conditions above are met.

The ECM detects that the commanded state of the driver and the actual state of the output circuit do not match for greater than 5 seconds.

DTCs P1485, P1486 and P1487 are type B DTCs.

DTCs P1485, P1486 and P1487 are type B DTCs.

DTCs P1485, P1486 and P1487 will not keep the cooling fans from operating. If one of these DTCs is set the HPCM 2 will command the cooling fans to 90%. If the cooling fans do not operate, refer to Cooling Fan Malfunction - DTC P148A-P148C for further diagnosis.

1. Vehicle OFF, disconnect the X2 harness connector at the K114B Hybrid Powertrain Control Module 2.
2. Vehicle in Service Mode, test for 3-4 V between the ECM cooling fan output circuit terminal X2-9 and ground. If less than the specified range, test the circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module. If greater than the specified range, test the circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.
3. If all circuits test normal, replace the K114B Hybrid Powertrain Control Module 2.

1. Perform the «Diagnostic System Check - Vehicle»(ref-487438-S13406627192012072300000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-487438-S08433352102012072300000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-487438-S20414004952012072300000) provides an overview of each diagnostic category.

1. DTCs P00B3, P00B4, P00B6, P0101, P0102, P0103, P0111, P0112, P0113, P0114, P0116, P0117 or P0118 are not set.
2. The engine run time is between 70 s and 30 min.
3. The engine coolant temperature (ECT) sensor at start-up is between -10°C to +59°C (14°F to 138°F).
4. The intake air temperature (IAT) sensor is between -7°C to +60°C (-4°F to +140°F).
5. The airflow into the engine is between 1 to 100 g/s.
6. The DTC runs once per ignition cycle when the above conditions are met.

The ECM detects the engine coolant thermostat is stuck open for at least 2.5 min.

DTC P2181 is a Type B DTC

DTC P2181 is a Type B DTC

1. Insufficient vehicle interior heating is an indication of improper thermostat operation.
2. The scan tool Desired ECT Sensor and the ECT Sensor parameters should be within 5°C (9°F) when the engine is at operating temperature.
3. A resistance condition in the ECT sensor circuits may cause this DTC. This condition results in a greater voltage on the ECT sensor signal circuit, which is interpreted by the ECM as a colder ECT.

Important Preliminary Inspections Before Starting

Before using the Symptom diagnosis, perform the following

1. Perform «Diagnostic System Check - Vehicle»(ref-487438-S13406627192012072300000) and verify all of the following items: Ensure that the engine control module (ECM) and indicator lamp are operating correctly. Ensure that there are no diagnostic trouble codes (DTCs) that are stored. Scan tool data is within a normal operating range.
2. Verify the customer concern.
3. Perform the Visual/Physical Inspection in this section. The visual/physical inspection is extremely important, and can lead to correcting a condition without additional testing. It may also help reveal the cause of an intermittent condition.
4. Locate the correct symptom. Perform the tests and inspections associated with the symptom.

Review the entire cooling system operation in order to familiarize yourself with the system functions. Refer to Cooling System Description and Operation , and Hybrid Cooling System Description and Operation .

Visual/Physical Inspection

Several of the symptom procedures call for a careful visual and physical inspection. This can lead to correcting a condition without further tests and can save time. This inspection should include the following areas

1. Ensure that all control module grounds are clean, tight, and correctly located.
2. Inspect cooling system hoses and pipes for splits, kinks, and proper connections. Inspect thoroughly for any type of a leak or a restriction.
3. Inspect for a dirty or restricted engine cooling radiator and HVAC condenser.
4. Inspect for aftermarket devices which could affect the operation of the Cooling System.
5. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
6. Inspect the surge tank reservoirs for the proper coolant level.

Symptom List

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

1. «Cooling Fan Malfunction - DTC P148A-P148C»(ref-487494-S19018652392012072300000)
2. «Engine Overheating»(ref-487508-S07310272362012072300000)
3. «Loss of Coolant»(ref-487508-S10104415102012072300000)
4. «Thermostat Diagnosis»(ref-487508-S14518536632012072300000)
5. «Engine Fails To Reach Normal Operating Temperature»(ref-487508-S34819324332012072300000)

Thermostat Diagnosis

Thermostat Diagnosis

Pressure Cap Testing

Special Tools

1. GE-42401-A Radiator Cap and Surge Tank Test Adapter
2. EN-24460-A Cooling System Pressure Tester

For equivalent regional tools, refer to Special Tools .

1. Remove the pressure cap.
2. Wash the pressure cap sealing surface with water.
3. Use the EN-24460-A cooling system pressure tester (1) with GE-42401-A radiator cap and surge tank test adapter (2) in order to test the pressure cap.
4. Test the pressure cap for the following conditions: Pressure release when the EN-24460-A cooling system pressure tester exceeds the pressure rating of the pressure cap. Maintain the rated pressure for at least 10 seconds. Note the rate of pressure loss.
5. Replace the pressure cap under the following conditions: The pressure cap does not release pressure which exceeds the rated pressure of the cap. The pressure cap does not hold the rated pressure.

Cooling System Leak Testing

Special Tools

1. EN-24460-A Cooling System Pressure Tester
2. GE-42401-A Radiator Cap and Surge Tank Test Adapter

For equivalent regional tools, Refer to Special Tools

1. Remove the pressure cap.
2. Test the operation of the pressure cap. Refer to «Pressure Cap Testing»(ref-487508-S33341410202012072300000) .
3. Wash the pressure cap mating surface with water.
4. Use the EN-24460-A Cooling System Pressure Tester with the GE-42401-A Radiator Cap and Surge Tank Test Adapter (2) in order to apply pressure to the cooling system. Do not exceed the pressure cap rating.
5. The cooling system should hold the rated pressure for at least 2 minutes. Observe the gauge for any pressure loss.
6. Repair any leaks as required.