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Engine Cooling System: Diagnosis Cadillac STS I facelift

Cooling System (Mechanical) ~3561 words

DIAGNOSTIC CODE INDEX

DTCDescription
DTC P0480 or P0481P0480: Cooling Fan Relay 1 Control Circuit P0481: Cooling Fan Relay 2 Control Circuit
DTC P0480, P0481, P0691, P0692, P0693, or P0694 (V6)P0480: Cooling Fan Relay 1 Control Circuit P0481: Cooling Fan Relay 2 Control Circuit P0691: Cooling Fan Relay 1 Control Circuit Low Voltage P0692: Cooling Fan Relay 1 Control Circuit High Voltage P0693: Cooling Fan Relay 2 Control Circuit Low Voltage P0694: Cooling Fan Relay 2 Control Circuit High Voltage
DTC P1258 (V6)P1258: Engine Coolant Overtemperature - Protection Mode Active
DTC P1258 (with RPO LC3 or LH2)P1258: Engine Coolant Overtemperature - Protection Mode Active
DTC P2600-P2603P2600: Auxiliary Coolant Pump Relay Control Circuit P2601: Auxiliary Coolant Pump Performance P2602: Auxiliary Coolant Pump Relay Control Circuit Low Voltage P2603: Auxiliary Coolant Pump Relay Control Circuit High Voltage

DIAGNOSTIC CODE INDEX

Diagnostic Starting Point - Engine Cooling

Begin the system diagnosis with the diagnostic system check. Refer to 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 circuits
  3. The identification of any stored DTCs and their status

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

Diagnostic Instructions

  1. Perform the «Diagnostic System Check - Vehicle»(ref-338149-S41903538652009081700000) prior to using this diagnostic procedure.
  2. «Strategy Based Diagnosis»(ref-338149-S37154416862009081700000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-338149-S02595537362009081700000) provide an overview of each diagnostic category.

Diagnostic Fault Information

CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Low Speed Cooling Fan Relay Control Circuit for Lo Fan Spd RelayP0480P0480P0480
Lo Fan Spd Relay Coil Voltage Supply CircuitP0480P0480P0480
Hi Speed Cooling Fan Relay Control Circuit for Hi Fan Spd RelayP0481P0481P0481
Hi Fan Spd Relay Coil Voltage Supply CircuitP0481P0481P0481

Conditions for Running the DTC

  1. The ignition is ON.
  2. The system voltage is between 9-18 volts.
  3. The relay control circuit is transitioned from OFF to ON or ON to OFF.

Circuit/System Testing

  1. Ignition OFF, disconnect the 3 cooling fan relays listed below: Lo fan SPD relay HI fan SPD relay Fan S/P relay
  2. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 85 of each relay and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
  3. Verify that a test lamp does not illuminate between the ignition circuit terminal 85 and the control circuit terminal 86 of each relay. If the test lamp illuminates, test the control circuit for a short to ground. If the circuit test normal, replace the ECM.
  4. Remove the test lamp.
  5. Ignition ON, command the affected relay ON using a scan tool. Verify the affected scan tool FC Relay Control Ckt. Short Volts Test Status parameter is OK. For the Lo Fan SPD relay, use the scan tool Fan Relay 1 command. For the HI Fan SPD and Fan S/P relays, use the scan tool Relay 2 and 3 command. If not the specified value, test the control circuit for a short to voltage. If the circuit tests normal, replace the ECM
  6. Install a 3A fused jumper wire between the control circuit terminal 86 and the ignition circuit terminal 85. Command the affected relay ON with a scan tool. Verify the scan tool Relay Control Ckt Short Volts Test Status parameter is Fault. If not the specified value, test the control circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  7. If all circuits and the ECM test normal, replace the affected relay.

Diagnostic Instructions (V6)

  1. Perform the «Diagnostic System Check - Vehicle»(ref-338149-S41903538652009081700000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-338149-S37154416862009081700000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-338149-S02595537362009081700000) provides an overview of each diagnostic category.

Diagnostic Fault Information (V6)

CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Relay Coil Ignition CircuitP0691, P0693P0480, P0481
Relay Switch Ignition Circuit**
Low Fan Speed Relay Control CircuitP0691P0480P0692
Hi Fan Speed Relay and Fan S/P Relay Control CircuitP0693P0481P0694
Relay Controlled Output Circuit****
*Fans inoperative without a DTC. **Fans always ON without a DTC.

Conditions for Running the DTC (V6)

  1. The ignition voltage is between 8-18 volts.
  2. The engine speed is more than 40 RPM.
  3. The ECM driver transitions from ON to OFF or from OFF to ON.

Conditions for Clearing the MIL/DTC (V6)

DTCs P0480, P0481, P0691, P0692, P0693, and P0694 are Type B DTCs.

Circuit/System Testing (V6)

  1. Ignition OFF, disconnect all three cooling fan relays.
  2. Ignition ON, verify that a test lamp illuminates between ground and the relay coil ignition circuit terminal listed below: Low and high speed fan relays terminal 85 S/P fan relay terminal 86 If the test lamp does not illuminate, test the relay coil ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the relay coil ignition circuit fuse is open, test all components connected to the ignition circuit and replace as necessary.
  3. Test for 2.6-4.6 volts between ground and the relay coil control circuit terminal listed below: Low and high speed fan relays terminal 86 S/P fan relay terminal 85 If less than the specified range, test the relay coil 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 coil control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  4. Connect a test lamp between the relay coil control circuit and the relay coil ignition circuit, terminals 85 and 86.
  5. Command the fan relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always OFF, replace the ECM.
  6. If all circuits test normal, test or replace the relay.

Component Testing (V6)

  1. Ignition OFF, disconnect the cooling fan relay.
  2. Test for 70-110 ohms between terminals 85 and 86. If the resistance is not within the specified range, replace the relay.
  3. Test for infinite resistance between the following terminals: 30 and 86 30 and 87 30 and 85 85 and 87 If not the specified range, replace the relay.
  4. Test for less than 2 ohms between terminals 30 and 87A. If greater than the specified range, replace the relay.
  5. Install a 20A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87. If greater than the specified range, replace the relay.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-338149-S41903538652009081700000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-338149-S37154416862009081700000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-338149-S02595537362009081700000) provides an overview of the diagnostic category.
  1. The engine is running for greater than 30 seconds.
  2. DTC P0116, P0117, P0118, or P0128 are not set.

Conditions for Setting the DTC (V6)

The EM detects that engine coolant temperature is greater than 136°C (277°F) for more than 1 second or a cumulative time of 10 seconds.

Action Taken When the DTC Sets (V6)

  1. DTC P1258 is a Type A DTC.
  2. The engine will operate in the Overheated Engine Protection Operating Mode.
  3. The instrument panel (IP) will illuminate the coolant indicator lamp and the driver information center (DIC), if equipped, may display a message.

Conditions for Clearing the DTC (V6)

DTC P1258 is a Type A DTC.

Diagnostic Instructions (with RPO LC3 or LH2)

  1. Perform the «Diagnostic System Check - Vehicle»(ref-338149-S41903538652009081700000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-338149-S37154416862009081700000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-338149-S02595537362009081700000) provides an overview of each diagnostic category.

Conditions for Running the DTC (with RPO LC3 or LH2)

  1. The engine is running.
  2. DTCs P0116, P0117, P0118, or P0128 are not set.

Conditions for Setting the DTC (with RPO LC3 or LH2)

Coolant temperature more than 131°C (267.8°F) for more than 7 seconds.

Action Taken When the DTC Sets (with RPO LC3 or LH2)

  1. DTC P1258 is a Type A DTC.
  2. The engine will operate in the Overheated Engine Protection Operating Mode.
  3. The instrument panel (IP) will illuminate the coolant indicator lamp and the driver information center (DIC), if equipped, may display a message.

Conditions for Clearing the DTC (with RPO LC3 or LH2)

DTC P1258 is a Type A DTC.

Circuit/System Testing (with RPO LC3 or LH2)

  1. Test the thermostat for correct operation. Refer to «Thermostat Diagnosis»(ref-338194-S03473611072009081700000) .
  2. Test the engine cooling system for overheating. Refer to «Engine Overheating»(ref-338194-S10729140912009081700000) .
  3. Inspect the water pump and coolant flow for correct operation. Refer to «Water Pump Replacement (V6)»(ref-338194-S08295661812009081700000) or «Water Pump Replacement (LC3)»(ref-338194-S26114230482009081700000) or «Water Pump Replacement (LH2)»(ref-338194-S12362747682009081700000) .
  4. Inspect the engine mechanical for worn/leaking/cracked cylinder heads and engine block. Refer to «Coolant in Combustion Chamber»(ref-338166-S12097806622009081700000) and «Coolant in Engine Oil»(ref-338166-S03748791282009081700000) for the 4.4L engine, or «Coolant in Combustion Chamber»(ref-338167-S36440247322009081700000) and «Coolant in Engine Oil»(ref-338167-S18491135302009081700000) for the 4.6L engine.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-338149-S41903538652009081700000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-338149-S37154416862009081700000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-338149-S02595537362009081700000) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Auxiliary Coolant Pump Relay ControlP2602P2600P2603
GroundP2600

Typical Scan Tool Data

CircuitShort to GroundOpenShort to Voltage
Operating Conditions: Component Commanded OFF Parameter Normal Range: The following illustrates the normal parameter state with no circuit conditions: Component OFF - OK for Open/Short Gnd test and Not Run for Short to Volts test Component ON - Not Run for Open/Short Gnd test and OK for Short to Volts test
Ignition VoltageFaultFault
Auxiliary Coolant Pump Relay ControlFaultFaultNot Run

Aux. Coolant Pump Ckt. Short Gnd, Open, and Short Volts Test Status - Component Commanded OFF

CircuitShort to GroundOpenShort to Voltage
Operating Conditions: Component Commanded ON Parameter Normal Range: The following illustrates the normal parameter state with no circuit conditions: Component OFF - OK for Open/Short Gnd test and Not Run for Short to Volts test Component ON - Not Run for Open/Short Gnd test and OK for Short to Volts test
Ignition VoltageNot RunNot Run
Auxiliary Coolant Pump Relay ControlNot RunNot RunFault

Aux. Coolant Pump Ckt. Short Gnd, Open, and Short Volts Test Status - Component Commanded ON

  1. Ignition OFF, disconnect the harness connector at the auxiliary coolant pump relay.
  2. Ignition ON, verify that a test lamp illuminates between the ignition voltage circuit terminal 85 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 all components connected to the ignition voltage circuit and replace as necessary.
  3. Test for 2.6-4.6 volts between the control circuit terminal 86 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 control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  4. Connect a test lamp between the control circuit terminal 86 and the ignition voltage circuit terminal 85.
  5. Command the auxiliary coolant pump relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always OFF, replace the ECM.
  6. If all circuits/connections test normal, test or replace the auxiliary coolant pump relay.

Component Testing

  1. Ignition OFF, disconnect the auxiliary coolant pump relay.
  2. Test for 70-110 ohms between terminals 85 and 86. If the resistance is not within the specified range, replace the relay.
  3. Test for infinite resistance between the following terminals: 30 and 86 30 and 87 30 and 85 85 and 87 If not the specified value, replace the relay.
  4. Connect a 20-amp fused jumper wire from the positive terminal of the battery to relay terminal 85. Connect a jumper wire from the negative terminal of the battery to relay terminal 86. Measure for less than 2 ohms between terminals 30 and 87 of the relay. If greater than the specified range, replace the relay.

Visual/Physical Inspection

  1. Inspect for aftermarket devices which could affect the operation of the Cooling System. Refer to «Checking Aftermarket Accessories»(ref-338151-S01119782592009081700000) .
  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. «Cooling Fan Always On (V6)»(ref-338194-S19140249342009081700000) or «Cooling Fan Always On (with RPO LC3 or LH2)»(ref-338194-S35394982842009081700000)
  2. «Cooling Fan Inoperative (V6)»(ref-338194-S06116001362009081700000) or «Cooling Fan Inoperative (w/RPO LC3 or LH2)»(ref-338194-S00846444062009081700000)
  3. «Engine Overheating»(ref-338194-S10729140912009081700000)
  4. «Loss of Coolant (LC3)»(ref-338194-S04917575742009081700000) or «Loss of Coolant (LH2, LY7, LLT)»(ref-338194-S31105212702009081700000)
  5. «Thermostat Diagnosis»(ref-338194-S03473611072009081700000)
  6. «Engine Fails To Reach Normal Operating Temperature»(ref-338194-S19017615182009081700000)
  7. «After Boil Coolant Pump Always On»(ref-338194-S24511889682009081700000)
  8. «After Boil Coolant Pump Inoperative»(ref-338194-S03531612282009081700000)
  9. «After Boil Coolant Pump Malfunction»(ref-338194-S04348310862009081700000)
  10. «Pressure Cap Testing (Powertrain)»(ref-338194-S11059816032009081700000)
  11. «Cooling System Leak Testing (Charge Air Cooling)»(ref-338194-S40141388852009081700000) or «Cooling System Leak Testing (Powertrain)»(ref-338194-S05168469262009081700000)
  1. Ignition OFF, disconnect each cooling fan relay one at a time.
  2. Ignition ON, observe that the cooling fans are not activated. If the fans are activated, test for a short to voltage in the relay controlled output circuit. If the fans are not activated, test or replace the cooling fan relay.
  1. Ignition OFF, disconnect each cooling fan relay one at a time.
  2. Ignition ON, observe that the cooling fans are not activated. If the fans are activated, test for a short to voltage in the relay controlled output circuit. If the fans are not activated, test or replace the appropriate cooling fan relay.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-338149-S41903538652009081700000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-338149-S37154416862009081700000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-338149-S02595537362009081700000) provides an overview of each diagnostic category.
  1. Ignition OFF, disconnect the cooling fan relays.
  2. Connect a 30A fused jumper between the relay switch circuit terminal 30 and the ground circuit terminal 87 at the S/P fan relay connector. This will complete the left side fan ground circuit. Leave this jumper in place for the remainder of this procedure.
  3. Ignition ON, verify that a test lamp illuminates between the relay switch ignition circuit terminal 30 and ground. If the test lamp does not illuminate, test the appropriate relay switch B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the relay switch B+ circuit fuse is open, test the relay controlled output circuit for a short to ground. If the circuit tests normal, test or replace the relay.
  4. Connect a 30A fused jumper between the relay switch B+ circuit terminal 30 and the relay controlled output circuit terminal 87. Verify the appropriate fan is activated If the appropriate fan does not activate, test the relay controlled output circuit for a short to ground or an open/high resistance. If the circuit tests normal, test the fan ground circuit for an open/high resistance. If the circuit tests normal, replace the fan.
  5. Install the S/P fan relay. Verify both fans activate at low speed. If both fans do not activate, test the relay controlled output circuit terminal 87A of the S/P fan relay for a short to ground or an open/high resistance.
  6. If all circuits test normal, test or replace the relay.
  1. Ignition OFF, disconnect the cooling fan relay.
  2. Test for 70-110 ohms of resistance between terminals 85 and 86. If the resistance is not within the specified range, replace the relay.
  3. Test for infinite resistance between the following terminals: 30 and 86 30 and 87 30 and 85 85 and 87 If not the specified range, replace the relay.
  4. Test for less than 2 ohms of resistance between terminals 30 and 87A. If greater than the specified range, replace the relay.
  5. Install a 20A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms of resistance between terminals 30 and 87. If greater than the specified range, replace the relay.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-338149-S41903538652009081700000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-338149-S37154416862009081700000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-338149-S02595537362009081700000) provides an overview of the diagnostic category.
IMPORTANTYou must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
  1. Ignition OFF, disconnect the S/P relay.
  2. Ignition ON, activate the cooling fan relay 1 with the 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 fan relays.
  4. Connect a 30A fused jumper between the normally-open switch contact terminals at the S/P 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 the low speed fan and the high speed fan relay connections and verify 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 an 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 fan and the high speed fan relay connections and verify fan activation. If the fan does not activate, test the relay switch voltage supply circuit for a short to ground or high resistance. If the circuit tests normal and its fuse is open, test all connected components and replace as necessary.
  7. If the circuits and fans test normal, replace the relay.
  1. Ignition OFF, disconnect FUEL COOL relay.
  2. Ignition ON, observe that the auxiliary coolant pump is not activated. If the pump is activated, test for a short to voltage in the relay controlled output circuit. If the pump is not activated, test or replace the relay.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-338149-S41903538652009081700000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-338149-S37154416862009081700000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-338149-S02595537362009081700000) provides an overview of each diagnostic category.
  1. Ignition OFF, disconnect the FUEL COOL Relay.
  2. Ignition ON, verify that a test lamp illuminates between the relay switch ignition circuit and ground. If the test lamp does not illuminate, test the relay switch ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the relay switch ignition circuit fuse is open, test the appropriate relay controlled output circuit for a short to ground. If the circuit tests normal, test or replace the relay.
  3. Connect a 10A fused jumper between the relay switch ignition circuit and the relay controlled output circuit. Verify the pump is activated If the pump activates, test or replace the relay.
  1. If the pump does not activate, test the relay controlled output circuit for a short to ground or an open/high resistance. If the circuit tests normal, test the pump ground circuit for an open/high resistance. If the circuit tests normal, replace the pump.
  1. Ignition OFF, disconnect the auxiliary coolant pump relay.
  2. Test for 70-110 ohms of resistance between terminals 85 and 86. If the resistance is not within the specified range, replace the relay.
  3. Test for infinite resistance between the following terminals: 30 and 86 30 and 87 30 and 85 85 and 87 If not the specified value, replace the relay.
  4. Install a 20A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms of resistance between terminals 30 and 87. If greater than the specified value, replace the relay.
  1. Test for a blockage or restriction in the auxiliary coolant pump lines and hoses.
  2. Test the pump coolant passage for a blockage or a restriction.
  3. Test the pump impeller for a seized or binding condition.

Diagnostic Aids

The engine may overheat due to an intermittent operation of one of the following components

  1. The after boil heater pump
  2. The coolant bypass solenoid
  3. The coolant bypass valve
  4. The mechanical cooling fan
  5. The electric cooling fans
  6. The thermostat

For electrical inspection of the cooling fans and the after boil heater pump, refer to Testing for Intermittent Conditions and Poor Connections .

StepActionValue(s)YesNo
DEFINITION: Engine temperature lamp comes ON and stays ON, or the temperature gage shows hot, or coolant overflows from the surge tank onto the ground while the engine is running.
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle
2Inspect the surge tank for low coolant. Is there a loss of coolant?Go to Loss of Coolant (LC3) or Loss of Coolant (LH2, LY7, LLT)Go to Step 3
3IMPORTANT: Do not allow the engine temperature to exceed the specified value. Start the engine and allow to reach normal operating temperature.Does the engine begin to exceed the specified value?107°C (225°F)Go to Step 4Go to Diagnostic Aids
4Inspect for loose, damaged, and/or missing of the following: The A/C condenser seals The front air deflector The side seals Repair the system as necessary. Does the engine still overheat?Go to Step 5Go to Step 18
5Using the J 23688 Coolant and Battery Fluid Tester, test for insufficient coolant concentration. See Special Tools . Is the coolant protection greater than the specified value?37°C (-34°F)Go to Step 6Go to Step 7
6Correct the coolant concentration as necessary. Does the engine still overheat?Go to Step 7Go to Step 18
7Inspect for obstructed radiator air flow or bent radiator fins. Is the radiator air flow obstructed?Go to Step 8Go to Step 9
8Clean the radiator. Refer to Radiator Cleaning (Charge Air Cooling) or Radiator Cleaning (Powertrain) . Does the engine still overheat?Go to Step 9Go to Step 18
9Inspect the drive belt tensioner. Refer to Drive Belt Tensioner Diagnosis for the 3.6L engine or Drive Belt Tensioner Diagnosis for the 4.6L engine. Is the drive belt tensioner working properly and is the tension correct?Go to Step 11Go to Step 10
10Replace the drive belt tensioner. Refer to Water Pump and Generator Belt Tensioner Replacement or Air Conditioning Compressor and Power Steering Pump Belt Tensioner Replacement for the 3.6L engine or Drive Belt Tensioner Replacement - Generator or Drive Belt Tensioner Replacement - Air Conditioning, Power Steering, and Water Pump for the 4.6L engine. Does the engine still overheat?Go to Step 11Go to Step 18
11Inspect the thermostat for proper operation. Refer to Thermostat Diagnosis . Does the thermostat operate properly?Go to Step 13Go to Step 12
12Replace the thermostat. Refer to Engine Coolant Thermostat Replacement (LY7) or Engine Coolant Thermostat Replacement (V6) or Engine Coolant Thermostat Replacement (LC3) or Engine Coolant Thermostat Replacement (LH2) . Does the engine still overheat?Go to Step 13Go to Step 18
13Inspect for an inoperative after boil coolant pump if equipped. Does the engine still overheat?Go to Step 14Go to Step 18
14Inspect for an inoperative cooling fan. Refer to Cooling Fan Inoperative (V6) or Cooling Fan Inoperative (w/RPO LC3 or LH2) or Fan Clutch Diagnosis . Does the engine still overheat?Go to Step 15Go to Step 18
15Inspect for blocked cooling system passages. Are the cooling system passages blocked?Go to Step 16Go to Step 17
16Replace the radiator. Refer to Radiator Replacement (LY7 Standard Cooling) or Radiator Replacement (LH2 Heavy Duty Cooling) or Radiator Replacement (LH2 With Out V92) or Radiator Replacement (LLT) . Does the engine still overheat?Go to Step 17Go to Step 18
17Replace the engine water pump. Refer to Water Pump Replacement (V6) or Water Pump Replacement (LC3) or Water Pump Replacement (LH2) . Did you complete the repair?Go to Step 18
18Operate the system in order to verify the repair. Did you correct the condition?System OKGo to Step 2
IMPORTANT
Do not allow the engine temperature to exceed the specified value.
  1. Perform the «Diagnostic System Check - Vehicle»(ref-338149-S41903538652009081700000) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(ref-338149-S37154416862009081700000) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(ref-338149-S02595537362009081700000) provides an overview of each diagnostic category.

Note. The power supply cord will read open due to an internal thermal switch if the ambient temperature is above -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.

The engine may fail to reach normal operating temperature due to an intermittent operation of one of the following components

  1. The thermostat
  2. The electric fan system
  3. The mechanical fan system

For electrical inspection of the electrical fan system, refer to Testing for Intermittent Conditions and Poor Connections .

StepActionYesNo
DEFINITION: Normal coolant temperature readings will be expected to vary from 88-104°C (190-220°F).
1Did you perform the Diagnostic System Check - Vehicle?Go to Step 2Go to Diagnostic System Check - Vehicle
2Verify that the engine fails to reach normal operating temperature. Is the engine failing to reach normal operating temperature?Go to Step 3Go to Diagnostic Aids
3Inspect the surge tank for low coolant. Is there a loss of coolant?Go to Loss of Coolant (LC3) or Loss of Coolant (LH2, LY7, LLT)Go to Step 4
4Inspect the thermostat for proper operation. Refer to Thermostat Diagnosis . Does the thermostat operate properly?Go to Step 6Go to Step 5
5Replace the thermostat. Refer to Engine Coolant Thermostat Replacement (LY7) or Engine Coolant Thermostat Replacement (V6) or Engine Coolant Thermostat Replacement (LC3) or Engine Coolant Thermostat Replacement (LH2) . Did you complete the repair?Go to Step 6
6Operate the system in order to verify the repair. Did you correct the condition?System OKGo to Step 2

Pressure Cap Testing

  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-338194-S08548216942009081700000) .
  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-338194-S08548216942009081700000) . 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

  1. Remove the charge air coolant pressure cap.
  2. Test the operation of the charge air coolant pressure cap. Refer to «Pressure Cap Testing (Powertrain)»(ref-338194-S11059816032009081700000) .
  3. Wash the charge air coolant pressure cap mating surface with water.
  4. Use the J 24460-01 (1) with J 46143 (2) in order to apply pressure to the charge air cooling system. See «Special Tools»(ref-338194-S08548216942009081700000) . Do not exceed the pressure cap rating.
  5. The charge air 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.
  1. Remove the pressure cap.
  2. Test the operation of the pressure cap. Refer to «Pressure Cap Testing (Powertrain)»(ref-338194-S11059816032009081700000) .
  3. Wash the pressure cap mating surface with water.
  4. Use the J 24460-01 (1) with J 42401 (2) in order to apply pressure to the cooling system. See «Special Tools»(ref-338194-S08548216942009081700000) . 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

StepActionYesNo
DEFINITION: Testing the engagement and disengagement of the fan clutch.
1Were you sent here from Symptoms or another diagnostic table?Go to Step 2Refer to Symptoms - Engine Cooling
2Is there excessive fan air noise?Go to Step 3Go to Step 4
3Fan air noise is normal during cold engine start up. Does the fan noise go away at normal engine operating temperature?Go to Step 13Go to Step 4
4IMPORTANT: The engine must be turned OFF and the engine temperature should be cold. Rotate the fan clutch.Does the fan clutch rotate?Go to Step 5Go to Step 14
5Visually inspect the fan blades for cracks, looseness or damage. Are the fan blades in good condition?Go to Step 6Go to Step 15
6Visually inspect the fan clutch for signs of silicone leakage. Slight silicone leakage may not effect the fan clutch engagement. Excess leakage will prevent the fan clutch from engaging. Is the silicone fluid leakage excessive?Go to Step 14Go to Step 7
7Inspect the fan clutch for proper installation. Move the fan blade back and forth in a lateral motion. Inspect for fan blade to fan clutch movement. Is the fan blade loose at the fan clutch?Go to Step 10Go to Step 8
8Inspect the fan clutch for wear. Move the fan blade back and forth in a lateral motion. IMPORTANT: Approximately 6.5 mm (1/4 in) movement at the tip of the fan blade is normal. Inspect for fan clutch lateral movement. Is the fan clutch lateral movement excessive?Go to Step 14Go to Step 9
9The fan clutch should have more turning resistance when the engine is at or above normal operating temperature. Does the fan clutch have more resistance when the engine temperature is raised?Go to Step 11Go to Step 14
10Tighten the fan. Refer to Fastener Tightening Specifications . Is the repair complete?Go to Step 15
11Perform a fan clutch engagement test. Ensure the engine coolant level is full. Ensure the cooling fan drive belt tension is correct and not slipping. Position and secure a thermometer between the fan clutch and the radiator. Ensure the cooling fan is disengaged before starting this test. Sufficiently cover the radiator grille to restrict the air flow. IMPORTANT: Do not allow engine temperature to exceed 121°C (250°F). Start the engine. Turn the A/C ON. Operate the engine at approximately 2,000 RPM. Inspect the thermometer reading when the fan clutch engages. Do not continue this test if the fan clutch does not engage between 85-96°C (185-205°F). Fan clutch engagement will be indicated by an increase in fan air noise, fan speed, and a drop of about 3-10°C (5-15°F) on the thermometer reading. Did the fan clutch engage between 85-96°C (185-205°F)?Go to Step 12Go to Step 14
12Once the fan clutch engages, perform the following steps: Uncover the radiator grille. Turn the A/C OFF. Operate the engine at approximately 2,500 RPM to reduce the engine operating temperature. Remove the thermometer. Did the engine return to normal operating temperature?Go to Step 13
13As the engine temperature returns to normal, the fan clutch will disengage, indicated by a reduction in fan air noise and fan speed. Did the fan clutch disengage?Go to Step 15Go to Step 14
14Replace the fan assembly. Refer to Fan Replacement (LY7) or Fan Replacement (LH2) . Is the repair complete?Go to Step 15
15Operate the fan clutch to verify proper operation. Did you find and correct the condition?System OKGo to Step 2
IMPORTANT
The engine must be turned OFF and the engine temperature should be cold.
IMPORTANT
Approximately 6.5 mm (1/4 in) movement at the tip of the fan blade is normal.
IMPORTANT
Do not allow engine temperature to exceed 121°C (250°F).

Charge Air Cooling System Coolant Level Inspection

  1. Remove the intake manifold sight shield. Refer to «Intake Manifold Sight Shield Replacement»(ref-338139-S02548253932009081700000) .
  2. Verify that the coolant is at the cold fill line on the charge air cooling system fill neck.
  3. Verify that the coolant is at the cold fill line on the charge air cooling system reservoir.
  4. Add coolant as necessary to the fill neck and reservoir to bring the coolant level to the cold fill line.
  5. Install the intake manifold sight shield. Refer to «Intake Manifold Sight Shield Replacement»(ref-338139-S02548253932009081700000) .

More articles — Engine Cooling System