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No. 17 Cooling System Concerns-Overheating

17 COOLING SYSTEM CONCERNS-OVERHEATING
DESCRIPTION 
  • The engine runs at higher than normal temperature/overheats.
POSSIBLE CAUSE 
  • Improper coolant level
  • Blown fuses
  • Coolant leakage
  • Excessive A/C system pressure
  • A/C system operation is improper
  • Improper water/anti-freeze mixture
  • Fans reverse rotation
  • Cooling air passage to radiator blockage
  • Poor radiator condition
  • Thermostat malfunction
  • Radiator hose damage
  • Improper or damaged radiator cap
  • Cooling fans are inoperative
  • Coolant overflow system malfunction
  • Improper tension of drive belt
  • Drive belt damage
  • Eccentric shaft bypass valve malfunction (stuck closed)
DIAGNOSTIC PROCEDURE

STEP INSPECTION RESULTS ACTION
1 Inspect the following:
  • Engine coolant level
  • Coolant leakage
  • Water and anti-freeze mixture
  • Radiator condition
  • Collapsed or restricted radiator hoses
  • Radiator pressure cap
  • Overflow system
  • Fan rotational direction
  • Cooling air passage to radiator
  • Fuses

Are all items normal?		 Yes Go to the next step.
No Service if necessary.
Repeat Step 1.
2 Turn the ignition switch to the ON position (engine off).
Retrieve any DTCs using the M-MDS.
(See ON-BOARD DIAGNOSTIC TEST ).
Are there any DTCs displayed?		 Yes Go to the applicable DTC inspection.
(See DTC TABLE ).
No Go to the next step.
3 Start the engine and run it at idle speed.
Turn the A/C switch on and the set blower fan to any speed.
Does the A/C compressor engage?		 Yes Go to Step 5.
No Inspect the following:
  • Refrigerant charging amount
  • Open circuit between A/C relay and PCM terminal 1I
  • Seized A/C magnetic clutch
  • A/C magnetic clutch malfunction

Repair or replace if necessary.
If all items are normal, go to the next step.
4 Start the engine and run it at idle speed.
Turn the A/C switch on and the set blower fan to any speed.
Measure the voltage at the PCM terminal 1AU.
Is the voltage normal?
(See PCM INSPECTION ).		 Yes Go to the next step.
No Inspect the following:
  • Refrigerant pressure switch operation
  • A/C switch is stuck open
  • Open or short circuit between refrigerant pressure switch and PCM terminal 1AU
  • Open circuit of blower motor fan switch and resistor (if blower motor does not operate)
  • Evaporator temperature sensor and A/C amplifier
5 Inspect the cooling fan control system operation.
(See ENGINE CONTROL SYSTEM OPERATION INSPECTION ).
Does the cooling fan control system work properly?		 Yes Go to the next step.
No Repair or replace the malfunctioning part according to the inspection results.
6 Is the drive belt normal?
(See DRIVE BELT DEFLECTION/TENSION INSPECTION ).		 Yes Go to the next step.
No Replace the drive belt.
(See DRIVE BELT REPLACEMENT ).
7 Is there any leakage around the heater unit in the passenger compartment? Yes Inspect and service the heater for leakage.
No Go to the next step.
8 Is there any leakage from coolant hoses and/or radiator? Yes Repair or replace the malfunctioning part according to the inspection results.
No Go to the next step.
9 Cool down the engine.
Remove the thermostat and inspect operation.
(See THERMOSTAT REMOVAL/INSTALLATION ).
(See THERMOSTAT INSPECTION ).
Is the thermostat normal?		 Yes Install the thermostat.
(See THERMOSTAT REMOVAL/INSTALLATION ).
Go to the next step.
No Replace the thermostat.
(See THERMOSTAT REMOVAL/INSTALLATION ).
10 Access the ECT PID.
(See ON-BOARD DIAGNOSTIC TEST ).
Inspect the readings on both the ECT PID and the water temperature gauge on the instrument cluster.
Is the ECT PID indication the same as the water temperature gauge readings?		 Yes Inspect the eccentric shaft bypass valve.
No If the water temperature gauge is in the normal range but the ECT PID is not the same as the water temperature gauge reading, inspect the ECT sensor.
(See ENGINE COOLANT TEMPERATURE (ECT) SENSOR INSPECTION ).
If the water temperature gauge on the instrument cluster indicates the cold range but the ECT PID is normal, inspect the water temperature gauge.
(See INSTRUMENT CLUSTER INSPECTION ).
11 Verify test results.
  • If normal, return to the diagnostic index to service any additional symptoms.
  • If the malfunction remains, inspect the related Service Bulletins and/or On-line Repair Information and perform repair or diagnosis.
    • If the vehicle is repaired, troubleshooting is completed.
    • If the vehicle is not repaired or additional diagnostic information is not available, reprogram the PCM if a later calibration is available. Retest.
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