A/C OFF or Non-A/C Model
- The cooling fans are actuated by the Engine Control Module (ECM) using a low-speed cooling fan relay and a high-speed cooling fan relay. On A/C-equipped vehicles, a series/parallel cooling fan relay is also used.
- The ECM will turn the cooling fans ON at low speed when the coolant temperature reaches 93 °C (199 °F) and at high speed when the coolant temperature reaches 97 °C (207 °F).
- The ECM will change the cooling fans from high speed to low speed at 94 °C (201 °F) and will turn the cooling fans OFF at 90 °C (194 °F).
A/C ON
- The ECM will turn the cooling fans on at low speed when the A/C system is ON. The ECM will change to high speed when the coolant temperature reaches 115 °C (239 °F) or the high side A/C pressure reaches 1,859 kPa (270 psi).
- The cooling fans will return to low speed when the coolant temperature reaches 113 °C (235 °F) and the high side A/C pressure reaches 1,449 kPa (210 psi).
Engine Overheats
| Checks | Action |
|---|---|
| Check for a loss of the coolant. | Add the coolant. |
| Check for a weak coolant solution. | Confirm that the coolant solution is a 50/50 mixture of ethylene glycol and water. |
| Check the front of the radiator for any dirt, any leaves, or any insects. | Clean the front of the radiator. |
| Check for leakage from the hoses, the coolant pump, the heater, the thermostat housing, the radiator, the core plugs, or the head gasket. | Replace any damaged components. |
| Check for a faulty thermostat. | Replace a damaged thermostat. |
| Check for retarded ignition timing. | Perform an ECM code diagnosis. Confirm the integrity of the timing belt. |
| Check for an improperly operating electric cooling fan. | Replace the electric cooling fan. |
| Check for radiator hoses that are plugged or rotted. | Replace any damaged radiator hoses. |
| Check for a faulty water pump. | Replace a faulty water pump. |
| Check for a faulty surge tank cap. | Replace a faulty surge tank cap. |
| Check for a cylinder head or an engine block that is cracked or plugged. | Repair the damaged cylinder head or the damaged engine block. |
ENGINE OVERHEATS DIAGNOSIS CHART
Loss of Coolant
| Checks | Action |
|---|---|
| Check for a leak in the radiator. | Replace a damaged radiator. |
| Check for a leak in the following locations: Surge tank Hose | Replace the following parts, as needed: Surge tank Hose |
| Check for loose or damaged radiator hoses, heater hoses, and connections. | Reseat the hoses. Replace the hoses or the clamps. |
| Check for leaks in the coolant pump seal. | Replace the coolant pump seal. |
| Check for leaks in the coolant pump gasket. | Replace the coolant pump gasket. |
| Check for an improper cylinder head torque. | Tighten the cylinder head bolts to specifications. Replace the cylinder head gasket, if needed. |
| Check for leaks in the following locations: Intake manifold Cylinder head gasket Cylinder block plug Heater core Radiator drain plug | Repair or replace any components, as needed, to correct the leak. |
LOSS OF COOLANT DIAGNOSIS CHART
Engine Fails to Reach Normal Operating Temperature or Cool Air from the Heater
| Checks | Action |
|---|---|
| Check to determine if the thermostat is stuck open or is the wrong type of thermostat. | Install a new thermostat of the correct type and heat range. |
| Check the coolant level to determine if it is below the MIN mark on the surge tank. | Add sufficient coolant to raise the fluid to the specified mark on the surge tank. |
ENGINE FAILS TO REACH NORMAL OPERATING TEMPERATURE OR COOL AIR FROM HEATER