Engine Cooling System: Diagnosis GMC Sierra III

Diagnostic Code Index

DIAGNOSTIC CODE INDEX

Diagnostic Instructions

1. Perform the «Diagnostic System Check - Vehicle»(ref-650999-S38140870152014081900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-650999-S18942452582014081900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-650999-S34767258932014081900000) provides an overview of each diagnostic category.

Diagnostic Fault Information

Conditions for Running the DTC

1. The ignition voltage is 11 volts or greater.
2. The engine speed is 400 RPM or greater.
3. The ECM driver transitions from ON to OFF or from OFF to ON.
4. DTCs P0480, P0691 and P0692 run continuously once the above conditions are met.

Conditions for Setting the DTC

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

Action Taken When the DTC Sets

1. DTCs P0480, P0691 and P0692 are Type B DTCs.

Conditions for Clearing the MIL/DTC

1. DTCs P0480, P0691 and P0692 are Type B DTCs.

Diagnostic Aids

1. A delay or ramp up of approximately 12 seconds may occur before the cooling fan activates or changes speed when being commanded with a scan tool.
2. When operating the cooling fans with a scan tool, the Commanded States should be exercised in order, from OFF to High or High to OFF. The cooling fan control module may disable the cooling fans if a Commanded State is skipped.

Circuit/System Testing

1. Ignition OFF, disconnect the following G10 Cooling Fan Motors. G10L Cooling Fan Motor Left. G10R Cooling Fan Motor Right.
2. Ignition ON, verify that a test lamp illuminates between the following terminals and ground. G10L Cooling Fan Motor Left - terminal 2 G10R Cooling Fan Motor Right - terminal 2 If the test lamp does not illuminate and the circuit fuse is good Ignition OFF, remove the test lamp and turn all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 ohms in the appropriate B+ circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse. If the test lamp does not illuminate and the circuit fuse is open Ignition OFF, remove the test lamp and turn all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for infinite resistance between the terminals listed below and ground. G10L Cooling Fan Motor Left - terminal 2. G10R Cooling Fan Motor Right - terminal 2 If less than infinite resistance, repair the short to ground in the circuit. If infinite resistance, replace the appropriate G10 Cooling Fan Motor. If the test lamp illuminates
3. Ignition OFF, disconnect the following G10 Cooling Fan Motors. G10L Cooling Fan Motor Left G10R Cooling Fan Motor Right
4. Connect a DMM, set on the diode setting, between the following terminals and ground. G10L Cooling Fan Motor Left - terminal 4 G10R Cooling Fan Motor Right - terminal 4
5. Ignition ON, verify the DMM reading is greater than 2.5 V or displays O.L. with the cooling fan commanded OFF. If 2.5 V or less Ignition OFF, all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Disconnect the K20 Engine Control Module harness connector X1. Test for infinite resistance between the appropriate G10 Cooling Fan Motor control circuit terminal 4 and ground. If less than infinite resistance, repair the short to ground in the circuit. If infinite resistance, replace the K20 Engine Control Module. If greater than 2.5 V or displays O.L.
6. Command the Cooling Fan ON to 90 % with a scan tool.
7. Verify the DMM reading is less than 1 V. If 1 V or greater Ignition OFF, disconnect harness connector X1 at the K20 Engine Control Module, ignition ON. Test for less than 1 V between the appropriate G10 Cooling Fan Motor control circuit terminal 4 and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V. Ignition OFF and all vehicle systems OFF, it may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 ohms in the G10 Cooling Fan Motor control circuit terminal 4, end to end. If 2 ohms or greater, repair the open/high resistance in the control circuit. If less than 2 ohms, replace the K20 Engine Control Module. If less than 1 V
8. Test or replace the appropriate G10 Cooling Fan Motor.

1. Perform the «Diagnostic System Check - Vehicle»(ref-650999-S38140870152014081900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-650999-S18942452582014081900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-650999-S34767258932014081900000) provides an overview of each diagnostic category.

The engine is operating.

All V8

1. The coolant temperature is warmer than 129°C (264°F) for greater than 10 seconds.
2. DTC P1258 runs continuously once the conditions above have been met.

6.0L - Hybrid

1. The coolant temperature is warmer than 132°C (270°F) for greater than 10 seconds.
2. DTC P1258 runs continuously once the conditions above have been met.

1. DTC P1258 is a Type A DTC.
2. The engine will operate in the Overheated Engine Protection Operating Mode.
3. The IP will illuminate the coolant temperature indicator lamp and the driver information center (DIC), if equipped, may display a message.
4. If the protection mode is active and an ECT sensor DTC sets, the protection mode will remain active at the start of the next drive cycle until the ECT sensor DTC runs and passes.

DTC P1258 is a Type A DTC.

Important Preliminary Inspections Before Starting

Before using the Symptom diagnosis, perform the following

1. Perform «Diagnostic System Check - Vehicle»(ref-650999-S38140870152014081900000) 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. Refer to «Control Module References»(ref-651024-S37773196412014081900000) for scan tool information.
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 cooling fan and cooling system operation in order to familiarize yourself with the system functions.

1. «Cooling Fan Description and Operation»(ref-651030-S07264127982014081900000)
2. «Cooling System Description and Operation»(ref-651030-S05847577902014081900000)

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 the 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 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 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. «Cooling Fan Always On»(ref-651030-S16758140472014081900000)
2. «Cooling Fan Inoperative»(ref-651030-S06286087172014081900000)
3. «Engine Overheating»(ref-651030-S32653475622014081900000)
4. «Loss of Coolant (L83)»(ref-651030-S07304076372014081900000) , «Loss of Coolant (LV3)»(ref-651030-S21083874402014081900000)
5. «Thermostat Diagnosis»(ref-651030-S18447543952014081900000)
6. «Coolant Heater Inoperative»(ref-651030-S10545185072014081900000)
7. «Engine Fails To Reach Normal Operating Temperature»(ref-651030-S24930984452014081900000)

1. Perform the «Diagnostic System Check - Vehicle»(ref-650999-S38140870152014081900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-650999-S18942452582014081900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-650999-S34767258932014081900000) provides an overview of each diagnostic category.

1. Certain resistance conditions with IAT or ECT sensors may cause unwarranted cooling fan activation. If the ECM is commanding the cooling fan ON for no apparent reason and without any component or system DTCs set, the IAT or ECT sensor may be skewed. If this condition is suspected, refer to the temperature versus resistance tables in the appropriate engine controls subsection.
2. The cooling fans will not operate when the scan tool Cooling Fan Motor Command parameter displays 0 %. This is a normal condition.

1. Perform the «Diagnostic System Check - Vehicle»(ref-650999-S38140870152014081900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-650999-S18942452582014081900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-650999-S34767258932014081900000) provides an overview of each diagnostic category.

A delay or ramp up of approximately 12 seconds may occur before the cooling fan activates or changes speed when being commanded with a scan tool.

1. Ignition OFF, disconnect the appropriate G10 Cooling Fan Motor harness connector.
2. Verify that a test lamp illuminates between ground circuit terminal 1 and B+. If the test lamp does not illuminate Ignition OFF and all vehicle systems OFF, it may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 ohms in the ground circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, repair the open/high resistance in the ground connection. If the test lamp illuminates
3. Verify that a test lamp illuminates between B+ circuit terminal 2 and ground. If the test lamp does not illuminate and the circuit fuse is good Ignition OFF, remove the test lamp and turn all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 ohms in the appropriate B+ circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse. If the test lamp does not illuminate and the circuit fuse is open Ignition OFF, remove the test lamp and turn all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for infinite resistance between the appropriate B+ circuit terminal and ground. If less than infinite resistance, repair the short to ground in the circuit. If infinite resistance, replace the appropriate G10 Cooling Fan Motor. If the test lamp illuminates
4. Ignition OFF, disconnect the other G 10 Cooling Fan Motor harness connector.
5. Ignition ON, test appropriate G 10 Cooling Fan Motor for 3-4 volts on the control circuit terminal 4. If 3 V or less Ignition OFF, all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down. Test for less than 2 ohms between the terminals listed below: G10L Cooling Fan Motor Left - terminal 4 G10R Cooling Fan Motor Right - terminal 4 If 2 ohms or greater, repair the open/high resistance in the circuit. If 3-4 V
6. Test or replace the appropriate G 10 Cooling Fan Motor.

Thermostat Test Procedure Using Glycol

Inspect the operation of the thermostat by hanging the thermostat on a hook in a 33 percent glycol solution.

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

1. Completely submerge the thermostat in a 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-650999-S38140870152014081900000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-650999-S18942452582014081900000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-650999-S34767258932014081900000) 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

Special Tools

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

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 / 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. J 24460-01 Cooling System Pressure Tester
2. J 42401 Radiator Cap/Surge Tank Test Adapter

1. Remove the pressure cap.
2. Test the operation of the pressure cap. Refer to «Pressure Cap Testing»(ref-651030-S01781323512014081900000) .
3. Wash the pressure cap mating surface with water.
4. Use the J 24460-01 cooling system pressure tester with the J 42401 radiator cap/surge tank test adapter 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.