Engine Cooling System: Diagnosis Chevrolet Silverado 2500 HD

DIAGNOSTIC CODE INDEX

DIAGNOSTIC CODE INDEX

Diagnostic Starting Point - Engine Cooling

Begin the system diagnosis with Diagnostic System Check - Vehicle . The Diagnostic System Check - Vehicle 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 DTCs and the codes status

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

Scan Tool Output Controls

Scan Tool Output Controls

Scan Tool Data List (V8)

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

Use the Scan Tool Data List only after the following is determined

1. The Diagnostic System Check - Vehicle is completed.
2. No diagnostic trouble codes (DTCs)
3. On-board diagnostics are functioning properly.

Scan tool values from a properly cooling system may be used for comparison with the system you are diagnosing. The Scan Tool Data List represents values that would be seen on a normal cooling system.

Only the parameters listed below are referenced in this service manual for use in diagnosis. If all values are within the typical range described below, refer to Symptoms - Engine Cooling for diagnosis.

The column labeled Data List indicates where a parameter can be located on the scan tool. Refer to 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 List (V8)

Diagnostic Instructions

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provide an overview of each diagnostic category.

Diagnostic Fault Information

DTC P0480 or P0481

Conditions for Running the DTC

1. The battery voltage is between 9-18 volts.
2. The engine speed is greater than 400 RPM.

Conditions for Setting the DTC

1. The commanded state of the output driver module (ODM) and the actual state of the control circuit do not match.
2. The condition is present for more than 5 seconds.

Action Taken When the DTC Sets

DTCs P0480 and P0481 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0480 and P0481 are Type B DTCs.

Diagnostic Aids

1. This test procedure requires that the vehicle battery has passed a load test and is completely charged. Refer to «Battery Inspection/Test»(ref-278006-S02520634812008012100000) .
2. When disconnecting electrical connectors or removing fuses and relays from a fuse block, always inspect the component electrical terminals for corrosion and the mating electrical terminals for tightness.
3. Use the J 35616 for any test that requires probing the underhood fuse block terminals, component wire harness terminals, or the ECM wire harness connector terminals.

Circuit/System Testing

P0480

1. Ignition OFF, disconnect the cooling fan low relay from the underhood fuse block.
2. Ignition ON, verify that a test lamp illuminates between the fan low relay coil voltage supply circuit and ground. If the test lamp does not illuminate, test the fan low relay coil voltage supply circuit for and open/high resistance.
3. Connect a test lamp between the fan low relay coil supply voltage circuit and the fan low relay coil control circuit. With a scan tool, command the fan relay 1 ON and OFF. Verify that the test lamp turns ON and OFF with each command. If the test lamp remains illuminated with each command, test the relay coil control circuit for a short to ground. If the circuit tests normal, replace the control module. If the test lamp does not illuminate, test the relay coil control circuit for and open or a short to voltage. If the circuit tests normal, replace the control module.
4. If the circuits test normal, replace the fan low relay.

P0481

1. Ignition OFF, disconnect the cooling fan high relay from the underhood fuse block.
2. Ignition ON, verify that a test lamp illuminates between the fan high relay coil voltage supply circuit and ground. If the test lamp does not illuminate, test the fan high relay coil voltage supply circuit for and open/high resistance.
3. Connect a test lamp between the fan high relay coil supply voltage circuit and the fan high relay coil control circuit. With a scan tool, command the fan relays 2 and 3 ON and OFF. Verify that the test lamp turns ON and OFF with each command. If the test lamp remains illuminated with each command, remove the fan control relay and retest. If the test lamp now turns ON and OFF with the fan control relay removed, replace the fan control relay. If the test lamp still remains illuminated when commanded ON and OFF, test the fan high relay coil control circuit for a short to ground. If the circuit tests normal, replace the control module. If the test lamp does not illuminate, test the fan high relay coil control circuit for and open or a short to voltage. If the circuit tests normal, replace the control module.
4. If all circuits test normal, replace the fan high relay.

Circuit Description

The engine control module (ECM) 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 132°C (270°F). When an over temperature condition is present, DTC P1258 will set. The ECM will disable 2 groups of 4 cylinders by turning OFF the fuel injectors. By switching between the 2 groups of cylinders, the ECM 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

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

1. The ECM 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

1. «Cooling System Description and Operation»(ref-277993-S08073831142008012100000)
2. «Cooling Fan Description and Operation»(ref-277993-S07798735612008012100000)

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the Cooling System. Refer to «Checking Aftermarket Accessories»(ref-278019-S10639375482008012100000) .
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-277993-S24384274602008012100000)
2. «Cooling Fan Inoperative»(ref-277993-S16932229562008012100000)
3. «Engine Overheating»(ref-277993-S20063544482008012100000)
4. «Loss of Coolant»(ref-277993-S42443381422008012100000)
5. «Thermostat Diagnosis»(ref-277993-S35569332182008012100000)
6. «Engine Fails To Reach Normal Operating Temperature»(ref-277993-S11118169912008012100000)

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

Low Engine Coolant Indicator Always On

When the low coolant indicator comes on, the engine shutdown warning light and audio alarm will also come on. When the engine shutdown warning light comes on with the audio alarm, the engine will shut down in approximately 30 seconds. Once the ignition key has been cycled, the engine will restart and run for 30 seconds. This will continue to happen until the low coolant indicator issue is resolved.

1. Ignition OFF, disconnect the harness connector at the coolant level switch.
2. Install a 3A fused jumper wire between the signal circuit terminal and ground.
3. Engine running, verify the low coolant indicator turns OFF. If the indicator does not turn OFF, test the signal circuit for an open/high resistance. If the indicator turns OFF, test the ground circuit for an open/high resistance.
4. If all circuits test normal, replace the coolant level switch.

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

1. Ignition OFF, disconnect the fan high relay.
2. Ignition ON, observe that both fans are now OFF. If both fans are OFF, replace the fan high relay. If either fan is still activated, remove the fan low relay. If both fans are now OFF replace the fan low relay. If either fan is still activated, test for a short to voltage in the fan voltage supply circuit.

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

The ECM has the capability of providing command to the fan relays even while a scan tool output control is being used. Always refer to the fan control command parameters on the scan tool to know which fans are being commanded ON by the ECM.

1. Ignition OFF, disconnect the series/parallel fan relay.
2. Ignition ON, activate the cooling fan relay 1 with a scan tool. The fan should be OFF. If the fan is activated, test the left fan ground circuit for a short to ground.
3. Ignition OFF, disconnect the remaining fan relays.
4. Connect a 30A fused jumper between the normally-open switch contact terminals at the fan control relay connector in order to complete the left fan ground circuit. Leave this jumper in place for the remainder of this procedure.
5. One at a time, connect a 30A fused jumper between the positive terminal at the battery and the fan voltage supply circuit terminal at each relay connection and verify the appropriate fan activation. If the appropriate fan does not activate, test the fan voltage supply circuit for a short to ground or open/high resistance. If the circuit tests normal, test the fan ground circuit for open/high resistance. If the circuits test normal, replace the fan.
6. Ignition ON, connect a 30A fused jumper between the relay switch voltage supply circuit terminal and the fan voltage supply circuit terminal at the low speed and then the high speed relay connections and verify the appropriate fan activation. If the appropriate fan does not activate, test the relay switch voltage supply circuit for a short to ground or high resistance.
7. If the circuits and fans test normal, replace the relay.

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»(ref-277993-S07049521082008012100000) . The thermostat should begin to open. J 24731 -206 tempil stick melts at 97°C (206°F). See «Special Tools»(ref-277993-S07049521082008012100000) . 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.

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

1. Test the engine coolant heater for an open or short to ground. If open or shorted, replace the heater.
2. If the heater tests normal, replace the coolant heater power cord.

1. Perform the «Diagnostic System Check - Vehicle»(ref-278018-S19353494792008012100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-278018-S03493196652008012100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-278018-S38264170562008012100000) provides an overview of each diagnostic category.

1. Test the engine coolant heater for an open or short to ground. If open or shorted, replace the heater.
2. If the heater tests normal, replace the coolant heater power cord.

Pressure Cap Testing

Tools required

1. J 24460-01 Cooling System Pressure Tester. See «Special Tools»(ref-277993-S07049521082008012100000) .
2. J 42401 Radiator Cap / Surge Tank Test Adapter. See «Special Tools»(ref-277993-S07049521082008012100000) .

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»(ref-277993-S07049521082008012100000) .
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»(ref-277993-S07049521082008012100000) . 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»(ref-277993-S07049521082008012100000) .
2. J 42401 Radiator Cap/ Surge Tank Test Adapter. See «Special Tools»(ref-277993-S07049521082008012100000) .

1. Remove the pressure cap.
2. Test the operation of the pressure cap. Refer to «Pressure Cap Testing»(ref-277993-S21232947022008012100000) .
3. Wash the pressure cap mating surface with water.
4. Use the J 24460-01 with the. See «Special Tools»(ref-277993-S07049521082008012100000) . J 42401 in order to apply pressure to the cooling system. See «Special Tools»(ref-277993-S07049521082008012100000) . 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.