Engine: Description and Operation
Engine Shutdown/Warning Protection System DescriptionDescription and Operation
If the system detects any of the following conditions: low engine oil pressure, low engine coolant level or high engine coolant temperature, the corresponding warning lamp and the engine shutdown warning lamp will turn on. If the engine shutdown warning light comes on, a tone alarm rings. If the engine shutdown feature is programmed, the engine will automatically shutdown in 30 seconds for engine protection. If the engine shuts down when the vehicle is still in traffic, it can restart and get another 30 seconds of operation.
Condition for Running the Engine Shutdown/ Warning Protection by Low Engine Oil Pressure
Following conditions are met for longer than 14 seconds.
- DTCs P0117, P0118, P0522 and P0523 are not set.
- The engine is running.
- The engine coolant temperature is more than 176° F (80° C).
- The engine oil pressure is less than 2.9 psi (20 kPa).
Condition for Running the Engine Shutdown/ Warning Protection by Low Engine Coolant Level
Following conditions are met for longer than 2 seconds.
- The engine is running.
- The engine coolant temperature is more than 185° F (85° C).
- The ECM detects a low coolant level signal from the engine coolant level control module.
Condition for Running the Engine Shutdown/ Warning Protection by High Coolant Temperature
Following conditions are met for longer than 3 seconds.
- DTCs P0117 and P0118 are not set.
- The engine is running.
- The engine coolant temperature is more than 253° F (123° C).
Engine Oil Pressure (EOP) Sensor
The engine oil pressure (EOP) sensor is installed to the engine cylinder block and it detects the engine oil pressure in the oil gallery. The EOP sensor provides a signal to the ECM on the signal circuit, which is relative to the engine oil pressure changes in the oil gallery. The ECM should detect a low signal voltage at a low engine oil pressure. The ECM should detect a high signal voltage at a high engine oil pressure. The ECM uses this value to monitor the condition of engine oil pressure and controls the engine shutdown/ warning protection function.
Engine Oil Pressure Warning Lamp & Engine Oil Pressure (EOP) Switch
The low engine oil pressure warning lamp on the instrument panel (IP) cluster is turned ON/ OFF by the engine oil pressure (EOP) switch (not EOP sensor). The EOP switch is installed to the oil filter housing and it detects the engine oil pressure in the oil gallery. The EOP switch closes the internal switch with low engine oil pressure (below 4.3 psi [29.4 kPa]), and the low engine oil pressure warning lamp circuit is pulled to the switch housing, which is ground.
Engine Coolant Level Sensor
The engine coolant level sensor is installed to the radiator upper housing and it detects the level of the engine coolant. The sensor has a signal circuit and a low reference circuit. When the engine coolant level is low, the sensor resistance is high (greater than 30k &). When the engine coolant level is normal, the sensor resistance decreases (less then 10k &). NOTE: The resistance of the engine coolant level sensor can only be measured using an LCR meter. A traditional OHM meter will not work.
Engine Coolant Level Control Module
There is an engine coolant level control module between the engine coolant level sensor and the engine control module (ECM) because the characteristics of the level sensor and the ECM are not compatible. The engine coolant level control module supplies an oscillation signal of 100HZ on the engine coolant level sensor circuit. When the engine coolant level is low, the engine coolant level control module detects a high voltage level on the engine coolant level sensor circuit and when the engine coolant level is OK, the module detects a lower voltage.
If the engine coolant level is low for longer than 38 seconds ±18 seconds consecutively or accumulatively (counter resets if the fault goes away for longer than 5 seconds), the engine coolant level control module will send a low signal to the ECM (supply a ground to the circuit between the engine coolant level control module and ECM). After 2 seconds of receiving this low signal, the ECM (depending on vehicle options programming) will illuminate the warning lamps and sound the alarm OR illuminate the warning lamps, sound the alarm and shut down the engine.
Engine Coolant Temperature (ECT) Sensor
The engine coolant temperature (ECT) sensor is installed to the thermostat housing. The ECT sensor is a variable resistor and it measures the temperature of the engine coolant. The sensor has a signal circuit and a low reference circuit. The ECM supplies 5 volts to the signal circuit and a ground for the low reference circuit. When the ECT sensor is cold, the sensor resistance is high. When the engine coolant temperature increases, the sensor resistance decreases. With high sensor resistance, the ECM detects a high voltage on the signal circuit. With lower sensor resistance, the ECM detects a lower voltage on the signal circuit. The ECM uses this value to calculate a fuel injection quantity, injection timing, EGR control and preheating control. The ECM also uses this value to control the engine shutdown/ warning protection function.
Overheat Warning Lamp & Engine Coolant Temperature Gauge
The engine coolant temperature gauge signal for the instrument panel (I/P) cluster is sent from the ECM through the controller area network (CAN) communication bus line. The overheat warning lamp on the IP cluster is turned ON by presetting temperature in the IP cluster. When the engine coolant temperature is higher than 248° F (120° C), the gauge needle reaches red zone and turns ON the overheat warning lamp.