Engine Cooling System: Diagnosis Chevrolet SSR 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 Output Controls

Powertrain Control Module Scan Tool Output Controls

Scan Tool Data List

Powertrain Control Module Scan Tool Data List

Instrument Panel Cluster Scan Tool Data List

Diagnostic Trouble Code (DTC) List

Diagnostic Trouble Code (DTC) List

Circuit Description

The following DTCs are for the cooling fan relay control circuits controlled by the powertrain control module (PCM)

1. DTC P0480 - low speed cooling fan relay control circuit
2. DTC P0481 - high speed cooling fan relay control circuit

Ignition 1 voltage is supplied to the cooling fan 1 relay from the IGN E fuse. The PCM controls the low speed cooling fan relay by grounding the low speed cooling fan relay control circuit.

Ignition 1 voltage is supplied to the cooling fan 2 relay from the IGN E fuse. The PCM controls the low speed cooling fan relay by grounding the low speed cooling fan relay control circuit.

The PCM grounds the cooling fan relay control circuits through an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line that is monitored by the PCM. When the PCM is commanding a component on, the voltage potential of the control circuit should be low, near 0 volts. When the PCM is commanding the control circuit to a component off, 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 effected driver will be disabled.

Conditions for Running the DTC

1. The ignition is ON.
2. The system voltage is between 9.0 and 18.0 volts.

Conditions for Setting the DTC

1. An improper voltage level has been detected on the cooling fan relay control circuit.
2. The condition is 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 the conditions that 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 Conditions and Poor Connections»(ref-187796-S06167208922005090100000) 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 occurs.
3. If the IGN E fuse is open, the DTC U0107 will be set as current DTC.

The engine control module (PCM) uses the engine coolant temperature (ECT) sensor to monitor the engine for an over temperature condition. This condition occurs when the coolant temperature is above 131° C (268° F). When an over temperature condition is present, DTC P1258 will set. The PCM will disable 2 groups of 4 cylinders by turning OFF the fuel injectors. By switching between the 2 groups of cylinders, the PCM is able to reduce the temperature of the coolant.

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC P1258 Engine Coolant Overtemperature-Protection Mode Active

The ignition is ON.

1. The PCM detects an ECT over 131° C (268° F).
2. The above condition is present for at least 3 seconds.

1. The PCM will illuminate the malfunction indicator lamp (MIL) during the first trip in which the diagnostic test has been run and failed.
2. The PCM will signal the instrument panel cluster (IPC) to turn ON the Service Engine Soon indicator.
3. The PCM will alternately disable 2 groups of 4 cylinders by turning OFF the fuel injectors.
4. The PCM will store conditions which were present when the DTC set in Freeze Frame Data.
5. The PCM will command the fan on high speed.

1. The PCM will turn the MIL OFF after 3 consecutive trips that 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 Clear DTC Information function.

DTC P1258

Symptoms - Engine Cooling

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the Cooling System. Refer to «Checking Aftermarket Accessories»(ref-187796-S08905438042005090100000) in Wiring Systems.
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 Always On»(ref-187839-S09530995412005090100000)
2. «Cooling Fan Inoperative»(ref-187839-S12383240552005090100000)
3. «Engine Overheating»(ref-187839-S30264421972005090100000)
4. «Loss of Coolant»(ref-187839-S16058200722005090100000)
5. «Thermostat Diagnosis»(ref-187839-S33129600982005090100000)
6. «Coolant Heater Inoperative»(ref-187839-S24159283242005090100000)
7. «Engine Fails To Reach Normal Operating Temperature»(ref-187839-S17733377312005090100000)

Thermostat Diagnosis

Tools Required

J 24731 Tempil Stick. See Special Tools and Equipment .

Use one of the following procedures in testing for a malfunctioning thermostat.

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). See «Special Tools and Equipment»(ref-187839-S19047857302005090100000) . The thermostat should begin to open. J 24731 -206 tempil stick melts at 97° C (206° F). See «Special Tools and Equipment»(ref-187839-S19047857302005090100000) . The thermostat should be fully open.
2. Replace the coolant thermostat if it does not operate properly between this temperature range.

Thermostat Test Procedure Using Glycol

Inspect the operation of the thermostat by hanging the thermostat on a hook in a 50/50 percent solution of DEX-COOL® and clean drinkable water.

In order to inspect if the thermostat valve is opening properly, perform the following test

1. Completely submerge the thermostat in the glycol solution. The solution should be 11° C (22° F) above the temperature indicated on the thermostat valve.
2. Thoroughly agitate the solution. Under these conditions, the thermostat valve should open.

In order to inspect if the thermostat valve is closing properly, perform the following test

1. Completely submerge the thermostat in a glycol solution. The solution should be 6° C (10° F) below the temperature indicated on the thermostat valve.
2. Thoroughly agitate the solution. Under these conditions, the thermostat valve should close completely.

Pressure Cap Testing

Tools Required

1. J 24460-01 Cooling System Pressure Tester. See «Special Tools and Equipment»(ref-187839-S19047857302005090100000) .
2. J 42401 Radiator Cap / Surge Tank Test Adapter. See «Special Tools and Equipment»(ref-187839-S19047857302005090100000) .

1. Remove the pressure cap.
2. Wash the pressure cap sealing surface with water.
3. Use the J 24460-01 (1) with J 42401 (2) in order to test the pressure cap. See «Special Tools and Equipment»(ref-187839-S19047857302005090100000) .
4. Test the pressure cap for the following conditions: Pressure release when the J 24460-01 exceeds the pressure rating of the pressure cap. See «Special Tools and Equipment»(ref-187839-S19047857302005090100000) . 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

Tools Required

1. J 24460-01 Cooling System Pressure Tester. See «Special Tools and Equipment»(ref-187839-S19047857302005090100000) .
2. J 42401 Radiator Cap / Surge Tank Test Adapter. See «Special Tools and Equipment»(ref-187839-S19047857302005090100000) .

1. Remove the pressure cap.
2. Test the operation of the pressure cap. Refer to «Pressure Cap Testing»(ref-187839-S20268879202005090100000) .
3. Wash the pressure cap mating surface with water.
4. Use the J 24460-01 (1) with J 42401 (2) in order to apply pressure to the cooling system. See «Special Tools and Equipment»(ref-187839-S19047857302005090100000) . Do not exceed the pressure cap rating.
5. The cooling system should hold the rated pressure for at least 2 minutes. Observe the gage for any pressure loss.
6. Repair any leaks as required.