W 250 Pickup L6-359 5.9L DSL (1989)
Powertrain Control Module: Description and Operation
MODES OF OPERATION
As input signals to the control module change, the control module adjusts the responses sent to the output devices. There are seven modes of operation
that determine how the control module responds to the various input signals.
The control module'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:
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Ignition switch ON
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Engine start-up (Crank)
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Engine warm-up
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Cruise or Idle
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Acceleration
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Deceleration
IGNITION SWITCH ON
When the ignition switch is turned to the ON position, the following actions occur:
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The control module receives battery voltage and an ignition sense input. Once the control module receives the ignition sense input, it becomes
activated and begins to interact with its input and output devices.
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The control module illuminates the Wait-To-Start lamp for approximately 2 seconds as a bulb check.
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The control module will monitor the input signal from the charge air temperature sensor. If the control module 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 control module will start the air intake heater preheat
cycle. When the control module starts this cycle, it illuminates the Wait-To-Start lamp until it is finished. The control module ENERGIZES the
air intake heaters by grounding the air intake heater relays.
NOTE: If the control module 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.
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The control module will illuminate the Water-In-Fuel lamp if a signal is sent to the control module from the Water-In-Fuel sensor.
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The control module 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:
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The control module receives a crank signal input when the starter relay is ENERGIZED.
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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.
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The control module monitors battery voltage, and if it senses that the battery voltage exceeds 12.66 volts, then it assumes the engine is running.
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If the control module 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 control module 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
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The control module 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).
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If the air intake temperature is at or below 54~F (12~C), then the thermistor is closed, allowing voltage to flow to the KSB solenoid. When the
intake air temperature increases above 60~F (16~C), the thermistor will open, DE-ENERGIZING the KSB solenoid.
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The control module will illuminate the Water-In-Fuel lamp if the Water-In-Fuel sensor senses excessive water in the fuel.
CRUISE OR IDLE
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The control module monitors the intake manifold air temperature based upon input signals from the charge air temperature sensor.
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If the air intake temperature is at or below 54~F (12~C), then the thermistor is closed, allowing voltage to flow to the KSB solenoid. When the
intake air temperature increases above 60~F (16~C), the thermistor will open, DE-ENERGIZING the KSB solenoid.
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If the air intake heater post-heat cycle is not finished, it will be completed in this mode.
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The control module will illuminate the Water-In-Fuel lamp if the Water-In-Fuel sensor senses excessive water in the fuel.
ACCELERATION
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If the air intake temperature is at or below 54~F (12~C), then the thermistor is closed, allowing voltage to flow to the KSB solenoid. When the
intake air temperature increases above 60~F (16~C), the thermistor will open, DE-ENERGIZING the KSB solenoid.
DECELERATION
