Engine Cooling System: Diagnosis GMC Cutaway G3500

Diagnostic Code Index

DIAGNOSTIC CODE INDEX

Diagnostic Instructions

1. Perform the «Diagnostic System Check - Vehicle»(ref-478441-S40412187692012061100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-478441-S09524533772012061100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-478441-S05742973822012061100000) provides an overview of each diagnostic category.

Diagnostic Fault Information

Typical Scan Tool Data

RCT Sensor

Conditions for Running the DTC

1. The ignition is ON, or the engine is running.
2. The battery voltage is greater than 9 V.
3. The intake air temperature (IAT) is warmer than -30°C (-22°F) or the IAT is colder than -30°C (-22°F) and the engine run time is greater than 120 s.
4. This DTC runs continuously within the enabling conditions.

Conditions for Setting the DTC

P00B3

The ECM detects that the RCT sensor signal is less than 0.27 V, which is warmer than 137°C (279°F) for greater than 2 s.

P00B4

The ECM detects that the RCT sensor signal is greater than 4.96 V, which is colder than-39°C (-38°F) for greater than 2 s.

Action Taken When the DTC Sets

1. DTCs P00B3 and P00B4 are Type B DTCs.
2. The cooling fans will be commanded ON.
3. The A/C compressor will be commanded OFF.

Conditions for Clearing the DTC

DTCs P00B3 and P00B4 are Type B DTCs.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the B34B Radiator Coolant Temperature Sensor.
2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal 2 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 Engine Control Module.
3. Ignition ON, verify the scan tool RCT sensor parameter is at -40°C (-40°F). If less than the specified range, test the signal circuit terminal 1 for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module.
4. Install a 3 A fused jumper wire between the signal circuit terminal 1 and the low reference circuit terminal 2. Verify the scan tool RCT sensor parameter is greater than 142°C (288°F). If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.
5. If all circuits test normal, test or replace the B34B Radiator Coolant Temperature Sensor.

Component Testing

Static Test

Measure and record the resistance of the B34B Radiator Coolant Temperature Sensor at various ambient air temperatures, then compare those measurements to the Temperature Versus Resistance table.

1. Perform the «Diagnostic System Check - Vehicle»(ref-478441-S40412187692012061100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-478441-S09524533772012061100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-478441-S05742973822012061100000) provides an overview of each diagnostic category.

Radiator Coolant Temperature Sensor

1. DTCs P00B3, P00B4, P0112, P0113, P0117, P0118 or P2610 are not set.
2. The ignition has been off for greater than 8 h before vehicle is started.
3. The ignition is ON, or the engine is running.
4. The intake air temperature (IAT) is greater than -7°C (19°F).
5. The fuel level is greater than 10%.
6. The DTC runs once per ignition cycle when the above conditions are met.

This DTC sets if one of the following conditions occurs for less than 1 s

1. The ECM detects the RCT sensor and the ECT sensor are greater than a predetermined intake air temperature at engine start-up.
2. The ECM detects the RCT sensor is 20°C (68°F) warmer than the ECT sensor at engine start-up and the block heater has not been detected.
3. The ECM detects the RCT sensor is 20°C (68°F) warmer than the ECT sensor at engine start-up and the engine has been cranking for greater than 10 s without a fuel level sensor DTC.

DTC P00B6 is a Type B DTC.

DTC P00B6 is a Type B DTC.

Diagnostic Aids

1. If the vehicle has sat overnight, the RCT sensor and the ECT sensor values should display within 3°C (5°F).
2. As the thermostat opens, the RCT sensor temperature should rise steadily, then stabilize once the thermostat opens completely.
3. Test the RCT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor.
4. Inspect for the correct operation of the engine cooling system and verify the correct coolant level.
5. If the condition is intermittent, allowing the vehicle to sit for greater than 8 h with the ignition OFF, may help isolate the condition. Compare the scan tool RCT and ECT temperature sensor values at Ignition ON. The RCT sensor and the ECT sensor values should display within 3°C (5°F).

1. Ignition OFF, disconnect the harness connector at the B34B Engine Coolant Temperature Sensor 2.
2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal 2 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 Engine Control Module.
3. Ignition ON, verify the scan tool B34B Engine Coolant Temperature Sensor 2 parameter is -40°C (-40°F). If greater than the specified range, test the signal circuit terminal 1 for a short to ground. If the circuit tests normal, replace K20 Engine Control Module.
4. Install a 1 A fused jumper wire between the signal circuit terminal 1 and the low reference circuit terminal 2. Verify the scan tool B34B Engine Coolant Temperature Sensor 2 parameter is at 150°C (302°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 Engine Control Module.
5. If all circuits test normal, test or replace the B34B Engine Coolant Temperature Sensor 2.

Static Test

1. Ignition OFF, disconnect the harness connector at the B34B Engine Coolant Temperature Sensor 2.
2. Test the B34B Engine Coolant Temperature Sensor 2 by varying the sensor temperature while monitoring the sensor resistance. Compare the readings with the table and verify that the resistance «Temperature Versus Resistance»(ref-478537-S08239586052012061100000) table and verify that the resistance is within 5% of the specification. If not within the specified range, replace the B34B Engine Coolant Temperature Sensor 2.

1. Perform the «Diagnostic System Check - Vehicle»(ref-478441-S40412187692012061100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-478441-S09524533772012061100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-478441-S05742973822012061100000) provides an overview of each diagnostic category.

FC Ckt, and FC Ckt 2 Open, Short Gnd, and Short Volts Test Status with Component OFF

FC Ckt, and FC Ckt 2 Open, Short Gnd, and Short Volts Test Status with Component ON

1. The ignition voltage is greater than 11 volts.
2. The engine is operating.
3. The engine speed is greater than 600 RPM.
4. DTC P0480 runs continuously when the conditions above exist for greater than 3 seconds.

The ECM detects that the commanded state of the ECM driver, and the actual state of the fan clutch solenoid control circuit do not match for greater than 1 second.

DTC P0480 is a Type B DTC.

DTC P0480 is a Type B DTC.

The scan tool FC Ckt 2 Test Status parameters can used in conjunction with the FC Ckt Test Status parameters to verify the integrity of the individual relay control circuits. If both the scan tool FC Ckt and FC Ckt 2 parameters indicate Fault in the respective Open Test Status then the condition is isolated to the portion of relay control circuit that is after the splice and common to both drivers. If Fault is indicated in only FC Ckt or FC Ckt 2, then the condition is isolated to the respective output driver and the portion of the circuit before the splice.

1. Ignition OFF, disconnect the fan clutch solenoid valve jumper harness connector.
2. Ignition ON, verify that a test lamp illuminates between the ignition voltage circuit terminal B and ground. If the test lamp does not illuminate, test the ignition voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition voltage circuit fuse is open, test the fan clutch solenoid and jumper harness for a short to ground.
3. Test for 3-4 V between solenoid control circuit terminal A and ground. If less than the specified range, test the control circuit for an open/high resistance or for a short to ground. If the circuit tests normal, replace the ECM. If greater than the specified range, test the relay control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
4. Connect a 3 A fused jumper wire between the solenoid control circuit terminal A and ground. Observe the scan tool Test Status parameters listed below: FC Ckt Short Gnd Test Status FC Ckt 2 Short Gnd Test Status Both parameters should transition from OK to Fault when the control circuit is connected to ground. If both parameters do not respond as specified, test the solenoid control circuit for a high resistance. If only one of the parameters responds as specified, test the appropriate solenoid control circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
5. If all circuits test normal, test or replace the cooling fan clutch assembly.

EV Fan Clutch Solenoid Valve Test-Static

1. Disconnect the fan clutch jumper harness connector X142.
2. Test for 5-12 ohms between terminal B and terminal A of the jumper harness connector. If not within the specified range, replace the fan clutch assembly.
3. Measure the resistance between the terminals listed below. The DMM should display OL. B and C B and D B and E B and the fan clutch housing/ground If less than the specified range, test the circuits of the jumper harness for an open/shorted condition. If the jumper harness tests normal, replace the cooling fan clutch assembly.

1. Perform the «Diagnostic System Check - Vehicle»(ref-478441-S40412187692012061100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-478441-S09524533772012061100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-478441-S05742973822012061100000) provides an overview of each diagnostic category.

FC Ckt, and FC Ckt 2 Open, Short Gnd, and Short Volts Test Status with Component OFF

FC Ckt, and FC Ckt 2 Open, Short Gnd, and Short Volts Test Status with Component ON

1. DTC P0016, P007C, P007D, P0112, P0113, P0117, P0118, P0335, P0336, P0340, P0341, P0480, P0495, or P0526 is not set.
2. The engine is operating for greater than 10 seconds.
3. The engine speed is between 1,200-3,429 RPM.
4. The BARO is greater than 75 kPa.
5. The engine coolant temperature is warmer than 70°C (158°F).
6. The ECM commanded fan clutch solenoid duty cycle is greater than 36 percent.
7. The cooling fan input shaft speed is steady.
8. DTC P0483 runs continuously every 100 mS when the conditions above exist.

1. The difference between the desired and the actual cooling fan speeds is 500 RPM or greater.
2. The condition exists for greater than 2 minutes.

DTC P0483 is a Type B DTC.

DTC P0483 is a Type B DTC.

The scan tool FC Ckt 2 Test Status parameters can be used in conjunction with the FC Ckt Test Status parameters to verify the integrity of the individual control circuits. If both the scan tool FC Ckt and FC Ckt 2 parameters indicate Fault in the respective Open Test Status then the condition is isolated to the portion of relay control circuit that is after the splice and common to both drivers. If Fault is indicated in only FC Ckt or FC Ckt 2, then the condition is isolated to the respective output driver and the portion of the circuit before the splice.

1. Ignition OFF, disconnect the fan clutch solenoid valve jumper harness connector X142.
2. Ignition ON, verify that a test lamp illuminates between the ignition voltage circuit terminal B and ground. If the test lamp does not illuminate, test the ignition voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition voltage circuit fuse is open, test the fan clutch solenoid and jumper harness for a short to ground.
3. Test for 3-4 V between the solenoid control circuit terminal A and ground. If less than the specified range, test the control circuit for an open/high resistance or for a short to ground. If the circuit tests normal, replace the ECM. If greater than the specified range, test the relay control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
4. Connect a 3 A fused jumper wire between the solenoid control circuit terminal A and ground. Observe the scan tool Test Status parameters listed below: FC Ckt Short Gnd Test Status FC Ckt 2 Short Gnd Test Status Both parameters should transition from OK to Fault when the control circuit is connected to ground. If both parameters do not respond as specified, test the solenoid control circuit for a high resistance. If only one of the parameters responds as specified, test the appropriate solenoid control circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
5. If all circuits test normal, test or replace the cooling fan clutch assembly.

EV Fan Clutch Solenoid Valve Test-Static

1. Disconnect the fan clutch jumper harness connector X142.
2. Test for 5-12 ohms between terminal B and terminal A of the jumper harness connector. If not within the specified range, replace the fan clutch assembly.
3. Measure the resistance between the terminals listed below. The DMM should display OL. B and C B and D B and E B and the fan clutch housing If less than the specified range, test the circuits of the jumper harness for an open/shorted condition. If the jumper harness tests normal, replace the cooling fan clutch assembly.

EV Fan Clutch Solenoid Valve Test-Dynamic

1. Ignition OFF, disconnect the fan clutch jumper harness connector X142.
2. Connect a 10 A fused jumper wire between terminal B of jumper harness connector and B+.
3. Connect a jumper wire to terminal A of the jumper harness connector.
4. Engine operating, connect the jumper wire from terminal A to ground. The fan should get much louder to indicate the clutch is engaged.
5. Disconnect the ground from the jumper wire connected to terminal A. The fan should become quiet to indicate the clutch is disengaged. If the fan clutch doesn't engage or disengage according to the test, replace the cooling fan clutch.

1. Perform the «Diagnostic System Check - Vehicle»(ref-478441-S40412187692012061100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-478441-S09524533772012061100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-478441-S05742973822012061100000) provides an overview of each diagnostic category.

1. DTC P0016, P0112, P0113, P0117, P0118, P0335, P0336, P0340, P0341, P0480, P0483, P0526, P2228, or P2229 is not set.
2. The engine is operating for greater than 10 seconds.
3. The engine speed is greater than 1,071 RPM.
4. The engine OFF time after the previous ignition cycle was greater than 0 seconds.
5. The ambient air temperature (AAT) is warmer than -40°C (-40°F).
6. The BARO is greater than 55 kPa.
7. The ECM commanded fan clutch solenoid duty cycle is less than 36 percent.
8. DTC P0495 runs continuously when the conditions above exist.

1. The cooling fan speed is greater than 1,500 RPM for greater than 80 seconds. OR
2. The clutch fluid pump-out, which is the time it takes for the fan clutch to disengage completely, is greater than a range of 10 minutes at sea level to 52 minutes at elevations of 6,500 ft.

DTC P0495 is a Type B DTC.

DTC P0495 is a Type B DTC.

1. Perform the «Diagnostic System Check - Vehicle»(ref-478441-S40412187692012061100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-478441-S09524533772012061100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-478441-S05742973822012061100000) provides an overview of each diagnostic category.

1. The engine is operating for greater than 10 S.
2. The engine speed is greater than 550 RPM.
3. The ECM commanded fan clutch solenoid duty cycle is greater than 45 percent.
4. DTC P0526 runs continuously when the conditions above exist for greater than 30 S.

1. The ECM detects a loss of cooling fan speed signal for greater than 300 mS.
2. The ECM detects that the cooling fan speed signal is greater or less than a predetermined threshold.
3. DTC P0526 sets if either condition exists for greater than 3 S.

DTC P0526 is a Type B DTC.

DTC P0526 is a Type B DTC.

1. Ignition OFF, disconnect the fan clutch harness connector X142.
2. 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 5 ohms between low reference circuit terminal C 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 ECM.
3. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal E and ground. If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM. If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
4. Test for 4.8-5.2 V between the signal circuit terminal D and ground. If less than the specified range, test for a short to ground or an open/high resistance. If circuit/connections test normal, replace the ECM. If greater than specified range, test for a short to voltage. If circuit/connections test normal, replace the ECM. If the circuit/connections test normal, test the circuits of the fan clutch jumper harness for an open/shorted condition.
5. If all the circuit/connections test normal, test or replace the cooling fan clutch assembly.

1. Perform the «Diagnostic System Check - Vehicle»(ref-478441-S40412187692012061100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-478441-S09524533772012061100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-478441-S05742973822012061100000) provides an overview of each diagnostic category.

The engine is operating.

The coolant temperature is warmer than 129°C (264°F) for greater than 10 seconds.

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

DTC P1258 is a Type A DTC.

1. Test the thermostat for correct operation. Refer to «Thermostat Diagnosis»(ref-478473-S03306989412012061100000) .
2. Test the fan clutch for proper operation. Refer to «Fan Clutch Diagnosis»(ref-478473-S30560708742012061100000) .
3. Test the engine cooling system for overheating. Refer to «Engine Overheating»(ref-478473-S26348010992012061100000) .
4. Inspect the water pump and coolant flow for correct operation. Refer to «Water Pump Replacement (V6)»(ref-478473-S18523385772012061100000) , «Water Pump Replacement (V8)»(ref-478473-S36698346402012061100000) , «Water Pump Replacement (LMF/LY2)»(ref-478473-S25112447092012061100000) .
5. Inspect the engine for worn/leaking/cracked cylinder heads and engine block. Refer to «Coolant in Combustion Chamber»(ref-478523-S38356762032012061100000) , and «Coolant in Engine Oil»(ref-478523-S41604643622012061100000) .

1. Perform the «Diagnostic System Check - Vehicle»(ref-478441-S40412187692012061100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-478441-S09524533772012061100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-478441-S05742973822012061100000) provides an overview of each diagnostic category.

1. DTCs P00B3, P00B4, P0101, P0102, P0103, P0112, P0113, or P0114 are not set.
2. The engine run time is between 70 s and 22 m.
3. The engine coolant temperature (ECT) sensor at start-up is between -20°C to +75°C (19 to 140°F).
4. The intake air temperature (IAT) sensor is between -7°C to +75°C (-4°F to +167°F).
5. The airflow into the engine is between 11 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 160 s.

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.
4. The mechanical thermostat will open at approximately 104°C (220°F). The mechanical thermostat will cycle from approximately 104°C (220°F) to approximately 98°C (208°F).

Important Preliminary Inspections Before Starting

Before using the Symptom diagnosis, perform the following

1. Perform «Diagnostic System Check - Vehicle»(ref-478441-S40412187692012061100000) 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-478463-S11680464072012061100000) 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 (w/LGH)»(ref-478473-S23181882732012061100000)
2. «Cooling System Description and Operation»(ref-478473-S16406822202012061100000)

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. «Engine Overheating»(ref-478473-S26348010992012061100000)
2. «Loss of Coolant»(ref-478473-S25495354912012061100000)
3. «Thermostat Diagnosis»(ref-478473-S03306989412012061100000)
4. «Coolant Heater Inoperative (without Diesel)»(ref-478473-S12204035502012061100000) , «Coolant Heater Inoperative (with Diesel)»(ref-478473-S17116497632012061100000)
5. «Engine Fails To Reach Normal Operating Temperature»(ref-478473-S23771421242012061100000)
6. «Fan Clutch Diagnosis»(ref-478473-S30560708742012061100000) , except diesel

1. Perform the «Diagnostic System Check - Vehicle»(ref-478441-S40412187692012061100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-478441-S09524533772012061100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-478441-S05742973822012061100000) provides an overview of each diagnostic category.

Note. Circuit/System Verification must be performed before performing the Circuit/System Testing.

1. Ignition OFF, disconnect the harness connector at the B33 coolant level switch.
2. Test for less than 5 ohms between the ground circuit terminal B and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
3. Engine operating, connect a 3 A fused jumper wire between the signal circuit terminal A and ground. Verify the low coolant indicator turns OFF. If the indicator does not turn OFF, test the signal circuit for short to ground. If the circuit tests normal, replace the P16 IPC.
4. If all circuits test normal, replace the B33 coolant level switch.

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»(ref-478473-S06617945892012061100000) -188 tempil stick melts at 87°C (188°F). The thermostat should begin to open. «J 24731»(ref-478473-S06617945892012061100000) -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.

1. Perform the «Diagnostic System Check - Vehicle»(ref-478441-S40412187692012061100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-478441-S09524533772012061100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-478441-S05742973822012061100000) 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-478441-S40412187692012061100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-478441-S09524533772012061100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-478441-S05742973822012061100000) provides an overview of each diagnostic category.

Note. The power supply cord will test open due to an internal thermal switch if the ambient temperature is warmer than -10°C (14°F). The thermal switch is designed to close when the ambient temperature is below -18°C (0°F).

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. «J 24460-01»(ref-478473-S06617945892012061100000) Cooling System Pressure Tester
2. «J 42401»(ref-478473-S06617945892012061100000) Radiator Cap/Surge Tank Test Adapter

1. Remove the pressure cap.
2. Wash the pressure cap sealing surface with water.
3. Use the «J 24460-01»(ref-478473-S06617945892012061100000) (1) with «J 42401»(ref-478473-S06617945892012061100000) (2) in order to test the pressure cap.
4. Test the pressure cap to verify the following conditions are met: Main pressure release occurs between 2 psi below and 5 psi above the rated cap pressure. The hold pressure reads greater than 3 psi below the rated cap pressure 60 seconds after initial pressure release.
5. Replace the pressure cap if the conditions in step 4 are not met.

Cooling System Leak Testing

Special Tools

1. «J 24460-01»(ref-478473-S06617945892012061100000) Cooling System Pressure Tester
2. «J 42401»(ref-478473-S06617945892012061100000) 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-478473-S08800223352012061100000) .
3. Wash the pressure cap mating surface with water.
4. Install the «J 42401»(ref-478473-S06617945892012061100000) to the surge tank.
5. Use the «J 24460-01»(ref-478473-S06617945892012061100000) in order to apply pressure to the cooling system. Do not exceed the pressure cap rating.
6. The cooling system should hold the rated pressure for at least 2 minutes. Observe the gauge for any pressure loss.
7. Repair any leaks as required.

Fan Clutch Diagnosis

Fan Clutch Diagnosis