Computers

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Computers
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Computers

• Use inputs to control outputs

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Inputs

• Most are from sensors
• Will usually be either an analog or digital
  voltage
• Most will supply an input similar to a
  potentiometer or have a varying frequency AC or
  DC signal

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Input types

• Insert sensor types here but shorten

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Specific inputs

• Insert sensors here but shorten

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Trouble codes

• A code stored in a computer to identify a
  specific type of fault
• Indication that something has gone outside of
  normal operating parameters for a specific period
  of time
• A function of the computers self diagnostic
  capabilities

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OBD1 (on-board diagnostics one)

• Began in late 1970s but was not made mandatory by
  federal govt. until 1990s
• Required all vehicles to perform self diagnostics
  to identify some major failures that can cause
  excessive emissions
• Most trouble codes could be flashed out on an
  indicator lamp

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OBD2 (on-board diagnostics two)

• Started appearing in 1994 and made mandatory on
  most vehicles in 1996
• Requires all vehicles to identify any failure
  that will result in exceeding the FTP by 1.5
• This includes identifying old catalytic
  converters, missfires, and evaporative systems
  failures

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OBD2

• Trouble codes are now universal and require the
  use of a scan tool to read
• DLC is now universal

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Trouble code access

• Can be gained by various methods
• Grounding a wire and counting flashes of bulb
• Grounding a wire and counting pulses of volt
  meter
• Unplugging the coolant temperature sensor and
  counting flashes

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Trouble code access

• Can be gained by various methods
• Cycling the key on and off three times and
  counting the flashes
• Through the data stream via a scan tool

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Trouble code types

• Current vs. History
• Just because the light is on does not mean
  problem is occurring
• Hard vs. Soft

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Trouble code diagnosis

• If problem is occurring use published
  diagnostics and grey matter
• If problem is not occurring the published
  diagnostics and charts can help but in almost
  every case can not be used directly
• If a vehicle has multiple codes, look for
  commonalties
• One malfunction can set multiple codes

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The End