OBD II

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OBD II

• Chapter 14
• Pg 433 Classroom Manual

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What is OBD II ?
433 Class manual

• On Board Diagnostics II
• Response to Federal Government
• Monitors when emissions increase by 50 percent
  or more.
• Calls for standard service procedure without
  dedicated special tools.
• Universal Diagnostic Test connector
• Standard list of Diagnostic Trouble codes

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OBD II MONITORS
Page 436C

• Catalyst Efficiency Monitor (437C)
• Misfire Monitor (438C)
• Fuel System Monitor (440C)
• Heated Oxygen Sensor Monitor (440C)
• EGR System Monitor (441C)
• Evaporative Emission System Monitor (442C)
• Secondary Air Injection System Monitor (442C)
• Comprehensive Monitor (444C)

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Catalyst Efficiency Monitor (437C)

• PCM monitors Oxygen sensors before catalyst and
  after catalyst
• Downstream sensors internal heater only turn on
  after engine is warm
• Catalyst stores oxygen and creates a low
  frequency signal
• If downstream O2 sensor signal reaches a certain
  frequency, DTC is set in memory

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Misfire Monitor (438C)

• If cylinder misfires, HC goes into cat and
  catalytic converter tries to convert and
  overworks itself.
• Type A misfire - immediate catalyst damage
• Type B misfire - cause emissions to rise 1.5
  times the design standard
• Type C misfire - could cause a I/M failure

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Fuel System Monitor (440C)

• Monitors air/fuel ratio in closed loop
• Short term fuel trim - Block Integrator is a
  short term correction of fuel delivery
• Long term fuel trim - Block Learn is a long term
  correction of fuel delivery
• If two drive cycle fuel trim corrections occur,
  PCM will set a DTC and illuminate the MIL.

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Heated Oxygen Sensor Monitor (440C)

• OBDII systems have primary and secondary Oxygen
  sensors
• Monitors O2 sensor switching times
• All O2s are monitored once per drive cycle
• PCM will vary fuel delivery and look for O2
  sensor response
• PCM must see O2 sensors signal within a certain
  range

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EGR System Monitor (441C)

• PCM monitors EGR operation by looking at MAP, or
  EGR temp, Delta pressure feedback sensor, etc.
• Operated once per OBDII trip
• If EGR pressure or temp is just a little out of
  range, will set a code
• If two drive cycles, will turn on MIL

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Non- Enhanced Evaporative Emission System
Monitor (442C)

• Monitors ability of fuel tank to hold vapors and
  ability of system to purge vapors
• System uses purge flow sensor
• Some systems use a Vapor Management Valve (VMV)

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Enhanced EVAP System

• EVAP Operation
• Power up Vac Test
• Excess Vac Test
• Loaded Canister Test
• Weak Vac Test
• Small Leak Test
• Purge Solenoid Test
• Should detect a .040 leak.

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Secondary Air Injection System Monitor (442C)

• Air injection is monitored for correct operation
• PCM tests system with passive and active tests
• Passive test - PCM just looks at operation of 02
  sensor
• Active test - PCM activates air injection to see
  reaction of O2 sensor if passive test fails.

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Comprehensive Monitor (444C)

• PCM monitors opens, shorts or input signal values
  that are out of range
• PCM checks voltage levels of inputs
• PCM checks frequency signals by performing
  rationality tests
• Looks at sensor readings to check if make sense
• Output state test - monitors output voltages

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SYSTEM READINESS MODE

• Warm Up Cycle - Engine Must rise at least 40
  degrees and reach 160 deg.
• Trip - Says at least five monitors must occur
  (not catalyst efficiency)
• Drive Cycle - Says five monitors plus catalyst
  efficiency must occur

PAGE 446C
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OBD II TRIP

• .Is when 5 monitors are completed.
• Misfire, Fuel, Comprehensive, EGR and HO2S.
• Each monitor requires specific driving
  conditions. (some once, some continuously)
• Scanner will tell you when a Trip is completed.

PAGE 446C
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OBD II TRIP
447 Classroom
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DRIVE CYCLE

• .is when all five plus catalyst monitor is
  completed
• If same fault detected during two drive cycles,
  DTC is stored
• If misfire occurs, will store code and turn on
  MIL immediately
• If catalyst monitor detects a fault in three
  drive cycles, it will set a code
• All faults erased after 40 ign. cycles

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OBD II DRIVE CYCLE
447 Classroom
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Data Link Connector (DLC)

• Mounted in standard location
• 16 pin with 9 pins defined by SAE
• Cannot jump across any pins to display codes on
  MIL
• Any Scanner should access Data Stream

Pg 450 Classroom
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LOCATION OF DLC

• Must be accessible from drivers seat
• Must be located between left of center and 300
  millimeters to the right of center
• Must not be hidden
• 9 Pins OBDII
• 7 Pins Manufacturer

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PCM Communication

• Federal regulations mandate common communication
  system
• OBDII systems use bi-directional communication
• Scanner can access data from any vehicle sold in
  the United States

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OBD II Scan Tools
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OBD II Programming

• EEPROM Programming
• Direct Programming
• Hooked directly from a PC to vehicle DLC
• Remote Programming
• Connected from PC to Scanner to DLC
• Scanner acts as a intermediary with Mass Storage
  Cartridge
• Off-Board Programming
• Used away from vehicle.
• Requires a Programming Adapter

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OBD II DIAGNOSIS

• Diagnostic systems will be standardized
• Scanners
• Codes
• Terminology
• Locations of DLCs
• Testing of Engine Control Systems
• Trouble code standardization

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Diagnostic Trouble Codes (DTCs)

• SAE J2012 specify format
• First Digit Area where code belongs
• P - Powertrain
• B - Body
• C - Chassis
• Second Digit Whos Responsible
• 0 - SAE
• 1 - Manufacturer

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DTCs

• Third Digit - Subgroup
• 0 - Total System
• 1 - Fuel-air control
• 2 - Fuel-air control
• 3 - Ignition System misfire
• 4 - Auxiliary Emission Systems
• 5 - Idle Speed Control
• 6 - PCM and Input/Output
• 7 - Transmission
• 8 - Non-EEC Powertrain

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DTCs

• Fourth and Fifth digits - Specific Area where
  trouble exists
• EXAMPLE P1711
• P - Powertrain DTC
• 1 - Manufacturer defined code
• 7 - Transmission Subgroup
• 11- Transmission oil temp (TOT) sensor and
  related circuit

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OBD II Diagnostic Codes
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SCANNER OPTIONS

• Some scanners have built in printer
• Some scanners have graph or lab scope
  capabilities
• Most scanners have freeze mode
• Some scanners have diagnostic information
  available such as common problems, technical
  service bulletins ref.
• Engine Analyzers have scanners also

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TEST SELECTIONS

• KOEO Test
• KOER Test
• Computed Timing
• Clear Memory
• Code Library
• Basic Test
• CDR Test
• Cruise Control Test

• Fault Codes
• Switch Tests
• ATM Tests
• Sensor Tests
• AIS Tests
• Output State Tests
• EMR reset
• Wiggle Test

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FREEZE FRAME MODE
Pg 609 Lab Manual

• Federal Regulations require engine operating
  conditions be captured whenever a MIL is
  illuminated.
• The latest failure will always overwrite a
  previous failure except misfire or fuel trim
  malfunctions.
• Some scanners will print out a graph showing
  sensor malfunctioning sensor signals

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