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H
Hydrogen
H/CMPR
High Compression
H2O
Water
HAC
High Altitude Compensator
HAIS
Heated Air Intake System (Chrysler)
HALL EFFECT
Process where current is passed through a small slice of semiconductor material at the same time as a magnetic field to produce a small voltage in the semiconductor.
HARD FAULT
Fault present during current engine operating cycle. Opposite of an intermittent fault which does not stay present.
HARD FAULT CODE
A circuit or component failure that reappears after codes have been cleared and the system has been retested.
HBV
Heater Blower Voltage
HC
Hydrocarbons
HCDS
High Clutch Drum Speed
HCV
Hydrocarbon (Ford)
HCV
Exhaust Heat Control Valve (Ford)
HD
Heavy Duty
HDC
Heavy Duty Cooling
HDR-CKP
High Data Rate CKP Sensor
HEATED OXYGEN SENSOR (HO2S)
The heated oxygen sensor monitors the oxygen content of the vehicle's exhaust gases, and generates a voltage signal (representing the air/fuel ratio) used by the vehicle's on-board computer for fuel control. The heated sensor contains a heating element to keep the sensor at consistent temperature, allowing the system to enter closed loop earlier and maintain closed loop operation with the engine at idle speed.
Heater Blower Voltage
Heater Blower Voltage input to EEC-IV processor reflecting heater blower voltage demand.
HEDF
High-speed Electro-Drive Fan relay or its circuit.
HEGO
Heated Exhaust Gas Oxygen Sensor
HEI
High Energy Ignition (GM)
HFC
High (speed) Fan Control
HFP
High Fuel Pump (Relay) Control
Hg (MERCURY)
A material used as a calibration standard for vacuum measurement.
HIC
Hot-Idle Compensator (Ford)
HIGH TENSION SECONDARY VOLTAGE
Voltage which enables current to jump the spark plug gap. This voltage is caused by the collapse of the magnetic field around the coil secondary windings.
HIGH-RESISTANCE SHORT
A short circuit which draws a slow current.
HLOS
Hardware Limited Operation System
HO
High Output
HO2S
Heated Oxygen Sensor
HO2S-1-1
Bank One Sensor One Signal
HO2S-1-2
Bank One Sensor Two Signal
HO2S-1-3
Bank One Sensor Three Signal
HO2S-2-1
Bank Two Sensor One Signal
HO2S-2-2
Bank Two Sensor Two Signal
hp
Horsepower
HPC
High Pressure Cutoff
HPL
High Pressure Liquid
HPS
High Performance System
HPV
High Pressure Vapor
HSC
High Swirl Combustion
HT
High Tension
HUD
Heads Up Display
HVAC
Heater Ventilation and Air Conditioning
HVACM
Heater-Vent-Air Conditioning Module
HVS
High Voltage Switch
Hz
Hertz
