Diagnostic Starting Point - Engine Cooling
Begin the system diagnosis with the diagnostic system check. Refer to Diagnostic System Check - Vehicle in Vehicle DTC Information. The Diagnostic System Check - Vehicle will provide the following information
- The identification of the control modules which command the system
- The ability of the control modules to communicate through the serial data circuits
- 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.
Scan Tool Data List
| Scan Tool Parameter | Data List | Units Displayed | Typical Data Value |
|---|---|---|---|
| Ignition Switch in RUN/Engine running/Automatic Transmission in PARK/Manual Transmission in NEUTRAL/Air Conditioner is OFF | |||
| ECT Sensor | Engine Data 1/Engine Data 2 | Degrees | 87°C (189°F) |
| ECT Sensor (6.5L) | Engine Data 1 | Volts | 2-3 Volts |
Powertrain Control Module (PCM) Scan Tool Data List
Circuit Description
The powertrain control module (PCM) 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 131°C (268°F). When an over temperature condition is present, DTC P1258 will set. The PCM will disable 2 groups of 4 cylinders by turning OFF the fuel injectors. By switching between the 2 groups of cylinders, the PCM 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
Conditions for Running the DTC
The engine is running.
Conditions for Setting the DTC
The PCM detects an engine over temperature condition.
Action Taken When the DTC Sets
- The PCM will illuminate the malfunction indicator lamp (MIL) during the first trip in which the diagnostic test has been run and failed.
- The PCM will turn ON the Service Engine Soon indicator.
- The PCM will alternately disable 2 groups of 4 cylinders by turning OFF the fuel injectors.
- The PCM will store conditions which were present when the DTC set as Freeze Frame and File Records data.
Conditions for Clearing the MIL/DTC
- The PCM will turn the MIL OFF after 3 consecutive trips that the diagnostic has been run and passed.
- The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
- The DTC can be cleared by using the scan tool Clear DTC Information function.
| Step | Action | Yes | No |
|---|---|---|---|
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Check the engine cooling fans for proper operation. Are the engine cooling fans operative? | Go to Engine Overheating | Go to Symptoms - Engine Cooling |
DTC P1258
Symptoms - Engine Cooling
| IMPORTANT | Review the system operation in order to familiarize yourself with the system functions. Refer to Cooling System Description and Operation . |
Visual/Physical Inspection
- Inspect for aftermarket devices which could affect the operation of the Cooling System. Refer to «Checking Aftermarket Accessories»(ref-197823-S24443069382005101300000) in Wiring Systems.
- Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
- Inspect the coolant recovery reservoir for the proper coolant level.
Symptom List
Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom
- «Engine Overheating»(ref-197849-S18739150282005101300000)
- «Loss of Coolant»(ref-197849-S09775128662005101300000)
- «Thermostat Diagnosis»(ref-197849-S09898578332005101300000)
- «Coolant Heater Inoperative»(ref-197849-S28515795012005101300000)
- «Engine Fails To Reach Normal Operating Temperature»(ref-197849-S02565115612005101300000)
- «Fan Clutch Diagnosis»(ref-197849-S06381950832005101300000)
Thermostat Diagnosis
Tools Required
J 24731 Tempil Stick. See Special Tools .
Use one of the following procedures in testing for a malfunctioning thermostat.
Thermostat Test Procedure Using Tempil Sticks
The coolant thermostat can be tested using a temperature (tempil) stick. The temperature stick is a pencil like device. It has a wax material containing certain chemicals which melt at a given temperature. Temperature sticks can be used to determine a thermostat's operating range, by rubbing 87°C (188°F) and 97°C (206°F) sticks on the thermostat housing.
- 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-197849-S10591011172005101300000) . The thermostat should begin to open. J 24731 -206 tempil stick melts at 97°C (206°F). See «Special Tools»(ref-197849-S10591011172005101300000) . The thermostat should be fully open.
- 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
- Completely submerge the thermostat in the glycol solution. The solution should be 11°C (22°F) above the temperature indicated on the thermostat valve.
- 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
- Completely submerge the thermostat in a glycol solution. The solution should be 6°C (10°F) below the temperature indicated on the thermostat valve.
- Thoroughly agitate the solution. Under these conditions, the thermostat valve should close completely.
Pressure Cap Testing
Tools Required
- J 24460-01 Cooling System Pressure Tester. See «Special Tools»(ref-197849-S10591011172005101300000) .
- J 42401 Radiator Cap/Surge Tank Test Adapter
- Remove the pressure cap.
- Wash the pressure cap sealing surface with water.
- Use the J 24460-01 (1) with J 42401 (2) in order to test the pressure cap. See «Special Tools»(ref-197849-S10591011172005101300000) .
- 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-197849-S10591011172005101300000) . Maintain the rated pressure for at least 10 seconds. Note the rate of pressure loss.
- 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
- J 24460-01 Cooling System Pressure Tester. See «Special Tools»(ref-197849-S10591011172005101300000) .
- J 42401 Radiator Cap/Surge Tank Test Adapter
- Remove the pressure cap.
- Test the operation of the pressure cap. Refer to «Pressure Cap Testing»(ref-197849-S40373959462005101300000) .
- Wash the pressure cap mating surface with water.
- Install the J 42401 to the surge tank.
- Use the J 24460-01 in order to apply pressure to the cooling system. See «Special Tools»(ref-197849-S10591011172005101300000) . Do not exceed the pressure cap rating.
- The cooling system should hold the rated pressure for at least 2 minutes. Observe the gage for any pressure loss.
- Repair any leaks as required.