Engine Cooling System: Diagnosis Chevrolet Silverado 3500

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

Hybrid Control Module (HCM) Scan Tool Output Controls

Instrument Cluster Scan Tool Output Controls

Starter Generator Control Module (SGCM) Scan Tool Output Controls

Scan Tool Data List

Instrument Panel Cluster (IPC) Scan Tool Data List

Powertrain Control Module (PCM) Scan Tool Data List

Hybrid Control Module (HCM) Scan Tool Data List

Starter Generator Control Module (SGCM) Scan Tool Data List

Diagnostic Trouble Code (DTC) List

Diagnostic Trouble Code (DTC) List

Circuit Description

The powertrain control module (PCM) uses the rationality diagnostic to determine if the sensor is skewed to a higher temperature range that would reduce the amount of time that would otherwise be spent with the engine off at idle. The PCM uses the intake air temperature (IAT) sensor input and the ambient air temperature sensor input from the HVAC control module to calculate the approximate ambient air temperature.

The HVAC control also monitors the ambient air temperature sensor and sends the data to the hybrid control module (HCM). The PCM monitors the intake air temperature sensor and sends the data to the HCM. The HCM uses these two data parameters to determine if the ambient air temperature sensor may not be with in range. If the HCM determines that the IAT sensor is 10° C (18° F) greater than the ambient air temperature sensor input, then DTC B0159 will set.

Conditions for Running the DTC

1. The following DTCs are not set as current in the PCM: P0112 P0113 P0502 P0503 P2610
2. The IAT input is not less than -7° C (19° F).
3. DTC B0159 is not set in the HVAC control module.
4. No loss of communication with the HVAC control module.
5. The ignition has been in the OFF position for 10 hours

Conditions for Setting the DTC

The IAT input is 10° C (18° F) greater than the ambient air temperature input for 1 second. The diagnostic is run 1 time during each ignition cycle.

Action Taken When the DTC Sets

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. The driver information center, if equipped, may display a message.

Conditions for Clearing the DTC

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

Diagnostic Aids

1. If DTC is set in the HVAC control module, perform that diagnostic first. Refer to «DTC B0159 or B0164»(ref-184159-S25608441442005082200000) in HVAC Systems - Automatic.
2. If condition is intermittent, refer to «Testing for Intermittent Conditions and Poor Connections»(ref-184114-S28299220792005082200000) in Wiring Systems.

The hybrid control module (HCM) controls the coolant pump operation by applying voltage to the coolant pump relay control circuit with an internal solid state device called a driver. When the HCM is commanding the relay ON, the voltage of the control circuit should be high, near 12 volts. When the HCM is commanding the relay OFF, the voltage potential of the control circuit should be low, near 0 volts.

The HCM monitors the relay control circuits for the following conditions

1. Short to ground
2. Short to voltage
3. An open circuit

If the HCM detects an improper voltage level on the coolant pump control circuit driver circuit, then DTC B3844 will set and the driver will be disabled.

1. The ignition switch is in the RUN or CRANK position.
2. DTC B1422 is not set.
3. The ignition 0 voltage circuit input is within 8 to 16 volts.

The HCM determines the state of the coolant pump relay control circuit is shorted to ground, open or shorted to power.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. The driver information center, if equipped, may display a message.

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

If the condition is not present, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

The PCM uses the ECT sensor to monitor the engine for an over temperature condition. This condition occurs when the coolant temperature is above 132° C (270° F). When an over temperature condition is present, DTC P1258 will set. The PCM will disable two groups of four cylinders by turning OFF the fuel injectors. By switching between the two groups of cylinders, the PCM is able to reduce the temperature of the coolant.

1. DTCs P0117, P0118, P1114, and P1115 are not active.
2. The engine is running.

The engine coolant temperature is above 132° C (270° F) for 10 seconds or more.

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 IPC to turn ON the Service Engine Soon indicator.
3. The PCM will alternately disable two groups of four cylinders by turning OFF the fuel injectors.
4. The PCM will store conditions which were present when the DTC set as Freeze Frame and File Records data.

Conditions for Clearing the MIL/DTC

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

The following DTCs are for the internal fluid temperature sensors located internal to the starter/generator control module (SGCM)

1. P0A01 is for the internal fluid temperature sensor 1 performance.
2. P0A02 is for the internal fluid temperature sensor 1 high temperature.
3. P0A03 is for the internal fluid temperature sensor 1 low temperature.
4. P1A7A is for the internal fluid temperature sensor 3 low temperature.
5. P1A75 is for the internal fluid temperature sensor 2 performance.
6. P1A76 is for the internal fluid temperature sensor 2 high temperature.
7. P1A77 is for the internal fluid temperature sensor 2 low temperature.
8. P1A78 is for the internal fluid temperature sensor 3 performance.
9. P1A79 is for the internal fluid temperature sensor 3 high temperature.

The SGCM monitors its internal fluid temperature sensors to control the SGCM coolant pump and SGCM cooling fan. The internal fluid temperature sensors of the SGCM are thermostats and are not serviceable. When the internal fluid temperatures are cold, the resistances of the sensors are high and the voltage signals are high. When the internal fluid temperatures are hot, the resistances of the sensors are low and the voltage signals are low. The input parameters are not displayed on the scan tool.

1. The engine has been running for 30 seconds.
2. The SGCM has received voltage on the ignition 0 voltage circuit.
3. The SGCM has turned ON and no configuration DTC are present.

1. For low temperature DTC the monitored internal fluid temperature of the sensor is below -40° C (-40° F).
2. For high temperature DTC the monitored internal fluid temperature of the sensor is above 125° C (257° F)
3. For performance DTC the monitored average internal fluid temperature of the sensor is 15° C (27° F) different than average of the all internal fluid temperature sensors.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. The driver information center, if equipped, may display a message.

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

DTC P0A01, P0A02, P0A03, P1A7A, P1A75, P1A76, P1A77, P1A78, or P1A79

The starter/generator control module (SGCM) coolant pump/fan relay supplies battery voltage to the SGCM coolant pump relay and the SGCM coolant fan relay. The SGCM monitors the temperature of the low side driver for the SGCM coolant pump/fan relay. The temperature sensor of the driver is not serviceable and the data for this sensor is not available on the scan tool. This internal driver temperature sensor aids in detecting a control circuit shorted to ground or a shorted relay coil.

1. The engine has been running for 30 seconds.
2. The SGCM coolant pump/fan relay has been commanded ON.

The SGCM detects an over temperature condition of the driver for the SGCM coolant pump/fan relay.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. The driver information center, if equipped, may display a message.

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

DTC P1AC0

The following DTCs are for the starter/generator control module (SGCM) coolant pump relay

1. P0A06 is for the SGCM coolant pump relay control circuit low voltage condition.
2. P0A07 is for the SGCM coolant pump relay control circuit high voltage condition.

The SGCM controls the coolant pump operation by applying voltage to the coolant pump relay control circuit with an internal solid state device called a driver. When the SGCM is commanding the relay ON, the voltage of the control circuit should be low, near 0 volts. When the SGCM is commanding the relay OFF, the voltage potential of the control circuit should be high, near 12 volts.

The SGCM monitors the relay control circuit for the following conditions

1. Short to ground
2. Short to voltage
3. An open circuit

If the SGCM detects an improper voltage level on the coolant pump control circuit, then DTC P0A06 or P0A07 will set and the driver will be disabled.

1. The engine has been running for 30 seconds.
2. The SGCM has received voltage on the ignition 0 voltage circuit.
3. The SGCM has turned ON and no configuration DTC are present.
4. For DTC P0A06 the SGCM coolant pump is commanded OFF.
5. For DTC P0A07 the SGCM coolant pump is commanded ON.

1. For DTC P0A06 the SGCM detects a low voltage condition on the SGCM coolant pump relay control circuit.
2. For DTC P0A07 the SGCM detects a high voltage condition on the SGCM coolant pump relay control circuit.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

If condition is not present, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

The following DTCs are for the starter/generator control module (SGCM) coolant fan relay

1. P1AC1 is for the SGCM coolant fan relay control circuit low voltage condition.
2. P1AC2 is for the SGCM coolant fan relay control circuit high voltage condition.

The SGCM controls the coolant fan operation by applying voltage to the coolant fan relay control circuit with an internal solid state device called a driver. When the SGCM is commanding the relay ON, the voltage of the control circuit should be low, near 0 volts. When the SGCM is commanding the relay OFF, the voltage potential of the control circuit should be high, near 12 volts.

The SGCM monitors the relay control circuits for the following conditions

1. Short to ground
2. Short to voltage
3. An open circuit

If the SGCM detects an improper voltage level on the coolant fan relay control circuit, then DTC P1AC1 or P1AC2 will set and the driver will be disabled.

1. The engine has been running for 30 seconds.
2. The SGCM has received voltage on the ignition 0 voltage circuit.
3. The SGCM has turned ON and no configuration DTC are present.
4. For DTC P1AC1 the SGCM coolant pump is commanded OFF.
5. For DTC P1AC2 the SGCM coolant pump is commanded ON.

1. For DTC P1AC1 the SGCM detects a low voltage condition on the SGCM coolant fan relay control circuit.
2. For DTC P1AC2 the SGCM detects a high voltage condition on the SGCM coolant fan relay control circuit.

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

If condition is not present, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

The starter/generator control module (SGCM) monitors its internal fluid temperature sensors to control the SGCM coolant pump and SGCM cooling fan. The internal fluid temperature sensors of the SGCM are thermistors and are not serviceable. When the internal fluid temperatures are cold, the resistances of the sensors are high and the voltage signals are high. When the internal fluid temperatures are hot, the resistances of the sensors are low and the voltage signals are low. The input parameters are not displayed on the scan tool. The SGCM calculates the estimated temperature of the electronics to interpret the total temperature of the SGCM. This value is displayed on the scan tool.

1. The engine has been running for 30 seconds.
2. The SGCM has received voltage on the ignition 0 voltage circuit.
3. The SGCM has turned ON and no configuration DTC are present.

The SGCM calculated temperature is over 100° C (212° F).

1. The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.
3. The SGCM functions are limited.

1. The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

If there is a restriction of the air flow through the radiator this DTC may set. Ensure that the vehicle front end has at least 1.5 meters (5 feet) of clearance from obstructions to airflow if vehicle is parked.

DTC P0A3E

The starter/generator control module (SGCM) monitors its internal fluid temperature sensors to control the SGCM coolant pump and SGCM cooling fan. The internal fluid temperature sensors of the SGCM are thermistors and are not serviceable. When the internal fluid temperatures are cold, the resistances of the sensors are high and the voltage signals are high. When the internal fluid temperatures are hot, the resistances of the sensors are low and the voltage signals are low. The input parameters are not displayed on the scan tool. The SGCM calculates the estimated temperature of the electronics to interpret the total temperature of the SGCM. This value is displayed on the scan tool.

1. The engine has been running for 30 seconds.
2. The SGCM has received voltage on the ignition 0 voltage circuit.
3. The SGCM has turned ON and no configuration DTC are present.

The SGCM calculated temperature is over 110° C (230° F).

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. The driver information center, if equipped, may display a message.
5. The SGCM shuts down and system will run on 12 volt system only.

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

If there is a restriction of the air flow through the radiator this DTC may set. Ensure that the vehicle front end has at least 1.5 meters (5 feet) of clearance from obstructions to airflow if vehicle is parked.

DTC P1A7E

The following DTCs are for the internal fluid temperature sensors located internal to the starter/generator control module (SGCM)

1. P1A7F is for the internal fluid level sensor 1 low voltage.
2. P1A80 is for the internal fluid level sensor 1 high voltage.
3. P1A81 is for the internal fluid level sensor 2 low voltage.
4. P1A82 is for the internal fluid level sensor 2 high voltage.
5. P1A83 is for the internal fluid level sensor 3 low voltage.
6. P1A84 is for the internal fluid level sensor 3 high voltage.
7. P1A85 is for the internal fluid level sensor 4 low voltage.
8. P1A86 is for the internal fluid level sensor 4 high voltage.

The SGCM electronics are immersed in an internal fluid to distribute the heat of the electronics evenly through the SGCM, this electronics internal fluid is not the coolant that is circulated through the SGCM cooling system. The SGCM monitors 4 separate internal fluid level sensors to determine if the electronics internal fluid level is low.

1. The engine has been running for 30 seconds.
2. The SGCM has received voltage on the ignition 0 voltage circuit.
3. The SGCM has turned ON and no configuration DTC are present.

1. For low voltage coolant level sensor indicates a temperature that is higher than its normal operating range
2. For high voltage coolant level sensor indicates a temperature that is lower than its normal operating range

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. The driver information center, if equipped, may display a message.

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

If the vehicle is on an extreme angle this DTC may set.

DTC P1A7F, P1A80, P1A81, P1A82, P1A83, P1A84, P1A85, or P1A86

The starter/generator control module (SGCM) electronics are immersed in an internal fluid to distribute the heat of the electronics evenly through the SGCM, this electronics internal fluid is not the coolant that is circulated through the SGCM cooling system. The SGCM monitors 4 separate coolant level sensors to determine if the electronics internal fluid level is low.

1. The engine has been running for 30 seconds.
2. The SGCM has received voltage on the ignition 0 voltage circuit.
3. The SGCM has turned ON and no configuration DTC are present.

All internal fluid level sensors are indicating a low internal fluid level.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The malfunction indicator lamp (MIL) will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. The driver information center, if equipped, may display a message.

1. A current DTC Last Test Failed clears when the diagnostic runs and passes.
2. A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Clear the DTC with a scan tool.

If the vehicle is on an extreme angle this DTC may set.

DTC P1A87

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-184114-S31353837752005082200000) 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 Overheated Indicator Always On»(ref-184167-S05942752562005082200000)
2. «Engine Coolant Temperature Indicator Always On»(ref-184167-S04825052272005082200000)
3. «Low Engine Coolant Indicator Always On»(ref-184167-S14054462852005082200000)
4. «Coolant Heater Inoperative»(ref-184167-S25883981742005082200000)
5. «Engine Overheating»(ref-184167-S32821469652005082200000)
6. «Loss of Coolant»(ref-184167-S36535832992005082200000)
7. «Thermostat Diagnosis»(ref-184167-S14777952282005082200000)
8. «Engine Fails To Reach Normal Operating Temperature»(ref-184167-S28097375882005082200000)
9. 119645
10. «Starter Generator Control Module Coolant Pump Inoperative»(ref-184167-S23178753712005082200000)
11. «Starter Generator Control Module Cooling Fan Always On»(ref-184167-S04665034872005082200000)
12. «Starter Generator Control Module Cooling Fan Inoperative»(ref-184167-S00202999702005082200000)
13. «Fan Clutch Diagnosis»(ref-184167-S34711806892005082200000)

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). 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.

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-184167-S07936639632005082200000) .
2. J 42401 Radiator Cap/Surge Tank Test Adapter. See «Special Tools and Equipment»(ref-184167-S07936639632005082200000) .

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.
4. Test the pressure cap for the following conditions: Pressure release when the J 24460-01 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.

Pressure Cap Testing - Starter/Generator Control Module

Tools Required

1. J 24460-01 Cooling System Pressure Tester. See «Special Tools and Equipment»(ref-184167-S07936639632005082200000) .
2. J 46143 Cooling System Adapter. See «Special Tools and Equipment»(ref-184167-S07936639632005082200000) .

Scheme 9

1. Follow the steps below in order to remove the starter/generator control module (SGCM) coolant tank cap. Slowly rotate the cap counterclockwise. Stop rotating and allow the hissing to stop. After all the hissing stops, continue turning counterclockwise in order to remove the cap.
2. Wash the pressure cap sealing surface with water.
3. Use the J 24460-01 (1) with the J 46143 in order to test the pressure cap.
4. Test the pressure cap for the following conditions: Pressure release when the J 24460-01 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

Tools Required

1. J 24460-01 Cooling System Pressure Tester. See «Special Tools and Equipment»(ref-184167-S07936639632005082200000) .
2. J 42401 Radiator Cap/Surge Tank Test Adapter. See «Special Tools and Equipment»(ref-184167-S07936639632005082200000) .

1. Remove the pressure cap.
2. Test the operation of the pressure cap. Refer to «Pressure Cap Testing»(ref-184167-S36338952562005082200000) .
3. Wash the pressure cap mating surface with water.
4. Use the J 24460-01 with the J 42401 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 gage for any pressure loss.
6. Repair any leaks as required.

Cooling System Leak Testing - Starter/Generator Control Module

Tools Required

1. J 24460-01 Cooling System Pressure Tester. See «Special Tools and Equipment»(ref-184167-S07936639632005082200000) .
2. J 46143 Cooling System Adapter. See «Special Tools and Equipment»(ref-184167-S07936639632005082200000) .

1. Follow the steps below in order to remove the starter/generator control module (SGCM) coolant tank cap. Slowly rotate the cap counterclockwise. Stop rotating and allow the hissing to stop. After all the hissing stops, continue turning counterclockwise in order to remove the cap.
2. Test the operation of the pressure cap. Refer to «Pressure Cap Testing - Starter/Generator Control Module»(ref-184167-S09315761702005082200000) .
3. Wash the pressure cap mating surface with water.
4. Use the J 24460-01 with the J 46143 in order to apply pressure to the cooling system. IMPORTANT: 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.

Fan Clutch Diagnosis

Fan Clutch Diagnosis

Inspection Procedure

1. Inspect the thermostats for sticking, cracks, and/or leakage of wax.
2. Replace the thermostats if damage is found.
3. Clean the thermostat housing and thermostat housing cover sealing surfaces.

1. Inspect the thermostats for sticking, cracks, and/or leakage of wax.
2. Replace the thermostats if damage is found.
3. Clean the thermostat housing and thermostat housing cover sealing surfaces.