B4000 Regular Cab 4WD V6-4.0L OHV (1997)
Powertrain Control Module (PCM): Description and Operation
Hardware Limited Operation Strategy
HLOS - HARDWARE LIMITED OPERATION STRATEGY
HLOS is a PCM function. HLOS provides minimal engine operation should the PCM stop functioning correctly. All modes of self-test are not
functional and electronic hardware is in control of system.
HLOS allowable output functions:
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Spark output controlled directly by PIP signal.
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Fixed fuel pulse width synchronized with PIP signal.
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Fuel pump energized.
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Idle speed control output signal functional.
HLOS disabled outputs to default state:
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EGR solenoids
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No converter lock-up.