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Home >> Dodge or Ram Truck >> 1991 >> W 350 Pickup L6-359 5.9L DSL >> Repair and Diagnosis >> Relays and Modules >> Relays and Modules - Powertrain Management >> Relays and Modules - Computers and Control Systems >> Engine Control Module >> Description and Operation >> Computerized

Computerized

MODES OF OPERATION

As input signals to the engine controller change, the engine controller adjusts the responses sent to the output devices. There are seven modes of operation that determine how the engine controller responds to the various input signals.

The engine controller's purpose is to achieve optimum fuel economy and performance combined with low emission levels. The diesel fuel injection system has the following modes of operation:

- Ignition switch ON
- Engine start-up (Crank)
- Engine warm-up
- Cruise or Idle
- Acceleration
- Deceleration
- Ignition switch OFF



IGNITION SWITCH ON

When the ignition switch is turned to the ON position, the following actions occur:

- The engine controller receives battery voltage and an ignition sense input. Once the engine controller receives the ignition sense input, it becomes activated and begins to interact with its input and output devices.
- The engine controller illuminates the Wait-To-Start lamp for approximately 2 seconds as a bulb check.
- The engine controller will monitor the input signal from the charge air temperature sensor. If the engine controller receives a signal from the charge air temperature sensor that the intake air temperature is at or less than 59~F (15~C), then the engine controller will start the air intake heater preheat cycle. When the engine controller starts this cycle, it illuminates the Wait-To-Start lamp until it is finished. The engine controller ENERGIZES the air intake heaters by grounding the air intake heater relays.
NOTE: If the engine controller receives an engine crank signal before the preheat cycle is finished, it will abort the preheat cycle and shut off the Wait-To-Start lamp.
- The engine controller will illuminate the Water-In-Fuel lamp if a signal is sent to the engine controller from the Water-In-Fuel sensor.
- The engine controller monitors battery voltage, and the air intake preheat cycle time is adjusted based on the current battery voltage.




ENGINE START-UP

The following actions occur when the starter motor is engaged:

- The engine controller receives a crank signal input when the starter relay is ENERGIZED.
- If the air intake preheat cycle is running, it will be aborted. The air intake heaters do not get ENERGIZED if an engine crank signal is sensed.
- The engine controller monitors battery voltage, and if it senses that the battery voltage exceeds 12.66 volts, then it assumes the engine is running.
- If the engine controller receives an engine cranking signal while the air intake preheat cycle is running, the air intake heaters will be DE-ENERGIZED. The post-heat cycle will begin if the engine controller receives an input from the battery indicating that the battery voltage is greater than 12.66 volts (indicating that the engine is running), and if the intake air temperature is at or less than 59~F (15~C).



ENGINE WARM-UP

- The engine controller will start the post-heat cycle if the intake air temperature, when the engine was started, was at or less than 59~F (15~C).
- If the air intake temperature is at or below 54~F (12~C), then the air temperature switch is closed, allowing voltage to flow to the KSB solenoid. When the intake air temperature increases above 60~F (16~C), the air temperature switch will open, DE-ENERGIZING the KSB solenoid.
- If the coolant temperature is below 60~F (16~C), the coolant temperature switch will close. If the engine controller receives a signal that the coolant temperature switch is closed, the transmission will not be allowed to shift into overdrive (automatic transmission). Once the coolant temperature reaches 60~F (16~C), then the coolant temperature switch will open and the transmission will be able to be shifted into overdrive.
- The engine controller will illuminate the Water-In-Fuel lamp if the Water-In-Fuel sensor senses excessive water in the fuel.


CRUISE OR IDLE

- The engine controller monitors the intake manifold air temperature based upon input signals from the charge air temperature sensor.
- If the air intake temperature is at or below 54~F (12~C), then the air temperature switch is closed, allowing voltage to flow to the KSB solenoid. When the intake air temperature increases above 60~F (16~C), the air temperature switch will open, DE-ENERGIZING the KSB solenoid.
- If the air intake heater post-heat cycle is not finished, it will be completed in this mode.
- The Throttle Position Sensor (TPS) and the Vehicle Distance (speed) Sensor are used to determine when the transmission can be shifted into overdrive.
- If the coolant temperature is below 60~F (16~C), the coolant temperature switch will close. If the engine controller receives a signal that the coolant temperature switch is closed, the transmission will not be allowed to shift into overdrive (automatic transmission). Once the coolant temperature reaches 60~F (16~C), then the coolant temperature switch will open and the transmission will be able to be shifted into overdrive.
- If the transmission thermo-switch is open, the transmission will not be allowed to be shifted into overdrive (automatic transmission). If the transmission thermo-switch opens while the transmission is in overdrive, then the transmission will be downshifted. The opening or closing of the transmission thermo-switch is dependant upon the temperature of the transmission fluid. The thermo-switch opens at 273~F (134~C), and closes when the transmission fluid drops to 240~F (116~C).
- The engine controller will illuminate the Water-In-Fuel lamp if the Water-In-Fuel sensor senses excessive water in the fuel.



ACCELERATION

- The Throttle Position Sensor (TPS) and the Vehicle Distance (speed) Sensor are used to determine when the transmission can be shifted into overdrive.
- If the coolant temperature is below 60~F (16~C), the coolant temperature switch will close. If the engine controller receives a signal that the coolant temperature switch is closed, the transmission will not be allowed to shift into overdrive (automatic transmission). Once the coolant temperature reaches 60~F (16~C), then the coolant temperature switch will open and the transmission will be able to be shifted into overdrive.
- If the air intake temperature is at or below 54~F (12~C), then the air temperature switch is closed, allowing voltage to flow to the KSB solenoid. When the intake air temperature increases above 60~F (16~C), the air temperature switch will open, DE-ENERGIZING the KSB solenoid.
- If the transmission thermo-switch is open, the transmission will not be allowed to be shifted into overdrive (automatic transmission). If the transmission thermo-switch opens while the transmission is in overdrive, then the transmission will be downshifted. The opening or closing of the transmission thermo-switch is dependant upon the temperature of the transmission fluid. The thermo-switch opens at 273~F (134~C), and closes when the transmission fluid drops to 240~F (116~C).
- If the speed control system is being used, and the resume/accelerate button is held, the engine controller will only allow the vehicle to accelerate at a predetermined rate. If the speed control system has been set, and the resume/accelerate button is momentarily pressed, the engine controller will accelerate the vehicle at two mile per hour increments.
- If the brakes are applied, the engine controller will de-activate the speed control system.




DECELERATION

- The Throttle Position Sensor (TPS) and the Vehicle Distance (speed) Sensor are used to determine when the transmission can be shifted into overdrive.
- If the coolant temperature is below 60~F (16~C), the coolant temperature switch will close. If the engine controller receives a signal that the coolant temperature switch is closed, the transmission will not be allowed to shift into overdrive (automatic transmission). Once the coolant temperature reaches 60~F (16~C), then the coolant temperature switch will open and the transmission will be able to be shifted into overdrive.
- If the transmission thermo-switch is open, the transmission will not be allowed to be shifted into overdrive (automatic transmission). If the transmission thermo-switch opens while the transmission is in overdrive, then the transmission will be downshifted. The opening or closing of the transmission thermo-switch is dependant upon the temperature of the transmission fluid. The thermo-switch opens at 273~F (134~C), and closes when the transmission fluid drops to 240~F (116~C).
- If the air intake temperature is at or below 54~F (12~C), then the air temperature switch is closed, allowing voltage to flow to the KSB solenoid. When the intake air temperature increases above 60~F (16~C), the air temperature switch will open, DE-ENERGIZING the KSB solenoid.
- If the speed control system is being used, and the coast/set button is held, the engine controller will only allow the vehicle to decelerate at a predetermined rate. If the coast/set button is released, while decelerating, the engine controller will reset the speed control to the rate of speed the vehicle was traveling when the coast/set button was released.
- If the brakes are applied, the engine controller will de-activate the speed control system.




IGNITION SWITCH OFF

When the key is placed in the OFF position, the engine controller still receives battery voltage. The engine controller needs battery voltage at all times to keep its memory alive. The memory stores TPS value from the previous Key-on and it stores fault codes.
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