1. Modern Automotive Technology PowerPoint for by Russell Krick
Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

2. Emission Control System
Chapter 44
Emission Control System
Testing, Service,
and Repair

3. Contents Computer-controlled emission system service
(16 Topics)
Computer-controlled emission system service
Emission maintenance reminder
Inspecting emission control systems
Exhaust gas analyzer
Emissions testing programs
Vacuum solenoid service

4. Contents PCV system service
Evaporative emissions control system service
Thermostatic air cleaner system service
EGR system service
Air injection system service
Pulse air system service

5. Contents Catalytic converter service Oxygen sensor service
Emission control information sticker
OBD II drive cycle

6. Emission System Service
Computer-Controlled
Emission System Service
Most emissions problems are caused by a malfunction in a system unrelated to the emission control system
fuel system
ignition system
exhaust system
computer control and electrical systems

7. Scanning Emission Systems
Connect the scan tool to the data link connector
Check for diagnostic trouble codes (DTC’s)
Retrieve data

8. Scanning Emission Systems

9. Scan Tool Readout
A. DTC
B. Description
C. Possible causes

10. Emission Maintenance Reminder
The circuit turns on a dash light to indicate the need for emission control system service
After repairs, the light must be turned off
Refer to the service manual for numerous procedures

11. Inspect vacuum hoses and wires
Inspecting Emission
Control Systems
Inspect vacuum hoses and wires

12. Inspecting Vacuum Hoses
Use a stethoscope to listen for vacuum leaks

13. Measures the chemical content of exhaust gas
Exhaust Gas Analyzer
Measures the chemical content of exhaust gas

14. Two-Gas Analyzer Measures two gases: hydrocarbons (HC)
carbon monoxide (CO)

15. Four-Gas Analyzer Measures four gases: hydrocarbons (HC)
carbon monoxide (CO)
carbon dioxide (CO2)
oxygen (O2)

16. Five-Gas Analyzer Measures five gases: hydrocarbons (HC)
carbon monoxide (CO)
carbon dioxide (CO2)
oxygen (O2)
oxides of nitrogen (NOx)

17. Analyzer with a calibration gas
Five-Gas Analyzer
Analyzer with a calibration gas

18. Using a Gas Analyzer Warm-up the analyzer
about 10 minutes
Zero and calibrate the analyzer
zero the meter while sampling shop air or calibration gas
Warm the vehicle to operating temperature
Insert a probe into the tail pipe through a hole in the shop’s vent hose

19. Analyzer Test Procedures
Two speed idle test
idle and 2500 rpm
Dynamometer test
loads the engine to simulate actual driving conditions
Compare the readings to specifications

20. Using a Gas Analyzer

21. Exhaust Gas Analyzer Readings

22. Hydrocarbons HC Measured in parts per million (PPM) by volume
Unburned gasoline
Newer vehicles have specifications of approximately 220 PPM

23. Carbon Monoxide CO Measured in percentage (%) by volume
Indicates incomplete burning of fuel or rich mixtures during combustion caused by insufficient air or excess fuel
Normal readings are below 1.5%

24. Oxides of Nitrogen NOx Measured in parts per million (PPM) by volume
Formed when nitrogen and oxygen in the cylinder combines
Occurs when combustion chamber temperatures are high

25. Carbon Dioxide CO2 Measured in percentage (%) by volume
Byproduct of normal combustion that occurs when one carbon atom combines with two oxygen atoms
Readings should be high, 8–15%

26. Oxygen O2 Measured in percentage (%) by volume
Typical readings should be 1–2% on a fuel-injected engine
Needed for the catalytic converter to burn HC and CO emissions
Indicator of a vehicle’s air-fuel mixture
High readings indicate a lean mixture

27. Emissions Testing Programs Exhaust gas readings are taken
idle and a set rpm (e.g rpm)
The vehicle may be checked for a catalytic converter, fuel inlet restrictor, and other emission control systems

28. IM 240
The vehicle is operated on a dynamometer at speeds up to 55 mph (89 kmh) for 240 seconds while exhaust gases are measured
The evaporative emissions system may be tested:
purge test
pressure test

29. Purge Test
Measures the flow of fuel vapors into the engine while performing the IM 240 test
A flow meter is installed into the purge line between the canister and the intake manifold
A computer compares the purge rate to specifications

30. Pressure Test Checks the system for leaks into the atmosphere
Pressure test equipment is connected to the evaporative emission system
A computer meters low pressure nitrogen into the system (0.5 psi, 3.4 kPa)
If the pressure drops too much, the computer will fail the system

31. Vacuum Solenoid Service
Refer to a vacuum hose diagram

32. Checking Solenoid Valves
Check vacuum hoses for hardening, cracks, and leaks

33. Checking Solenoid Valves
Use a multimeter to check for voltage to the solenoid

34. Checking Solenoid Valves
Use a vacuum pump to check solenoid vent/hold

35. Checking Solenoid Valves

36. PCV System Service
A faulty PCV system can increase emissions, cause engine sludging, wear, and idle quality problems
A leaking system can cause lean mixture
A plugged system can cause a rich mixture

37. PCV Maintenance Manufacturers recommend periodic maintenance
Inspect hoses, grommets, fittings, and breather hoses
Clean or replace the breather filter
Check or replace the PCV valve

38. PCV Testing Remove the valve from the grommet and shake it
The valve should rattle freely
Start the engine and plug the valve with your finger
You should feel vacuum
The engine speed should drop 40–80 rpm on carbureted engines
A special tester may be used

39. PCV Testing

40. PCV Test / Gas Analyzer Run the engine at idle; note the readings
Pull the PCV valve out of the grommet; note the readings
Compare the readings
If O2 and CO do not change, the PCV system is plugged
If O2 goes up more than 1% or CO goes down more than 1%, the oil may be diluted with gasoline or excess blowby

41. Evaporative Emissions Control System Service
Symptoms:
fuel odor
fuel leakage
fuel tank collapse
excess pressure in fuel tank
rough idle

42. Maintenance and Repair
Clean or replace the canister filter when specified
Inspect the fuel tank cap and pressure test it for leakage
Inspect all hoses for deterioration
Replace with fuel-resistant hose

43. Canister Filter Replacement

44. Use a vacuum pump to check the diaphragm or solenoid vent/hold
Purge Valve Check
Use a vacuum pump to check the diaphragm or solenoid vent/hold

45. Thermostatic Air Cleaner
System Service
If the flap remains in the cold air position all the time, the engine may miss and hesitate
If the flap stays in the hot air position, the engine could perform poorly when at full operating temperature

46. Maintenance and Testing
Visually inspect the following parts:
hoses
hot air tube
exhaust manifold heat shroud
sensor and vacuum motor operation

47. Checking Operation A. Watch the door action
B. Apply vacuum to the motor

48. EGR System Service Symptoms: stalling at idle rough idle detonation
lean mixture
emissions testing NOx failure

49. EGR Testing Refer to a service manual
Warm the engine to operating temperature
Quickly increase engine speed to 2500–3000 rpm
The valve pintle should move
With the engine idling, apply vacuum to the valve with a hand pump
The engine should miss or stall, indicating EGR flow

50. EGR Testing

51. Testing (Electronic Type)
A scan tool may allow you to observe the valve status or drive the valve open manually
An oscilloscope can be used to observe the solenoid drive signal or feedback signal from a pintle position sensor

52. Testing (Electronic Type)
Oscilloscope connections

53. Testing (Electronic Type)
Solenoid drive signal

54. Testing (Electronic Type)
Pintle position sensor feedback signal

55. Air Injection System Service Symptoms: backfiring noise
increased HC and CO emissions

56. Maintenance Replace the pump inlet filter if specified
Adjust the belt tension
Inspect the hoses and components

57. Testing Use an exhaust gas analyzer
Run the engine and note the readings
Disable the air injection system by pinching or disconnecting the pump discharge hose
O2 should drop 2–5%
HC and CO should increase
If no change is noted, the system is not working

58. The pump should produce 2–3 psi (14–21 kPa)
Pump Output Check
The pump should produce 2–3 psi (14–21 kPa)

59. Catalytic Converter Service
Problems are caused by contamination, overheating, and extended service
A plugged converter can cause high exhaust back pressure and loss of power
Pellet-type converters may be drained and refilled with new pellets

60. Plugged Catalytic Converter

61. Backpressure Test
Install a pressure gauge in the O2 sensor hole; compare the pressure to specifications

62. Gas Analyzer Test
Run the engine and catalytic converter to operating temperature, and note the readings
If oxygen is 1–2% or more, and CO is high (above 0.5 %), the converter is not oxidizing

63. Converter Replacement
Replace all gaskets, rubber mounts, and hardware

64. Oxygen Sensor Service
Sensors become coated or fouled with exhaust byproducts
Fuel economy and emissions may be affected
A “lazy” or “dead” O2 sensor will change resistance or voltage slowly, or not at all, with changes in the exhaust gas oxygen level

65. Testing Connect a scan tool, check for diagnostic trouble codes
Observe the O2 sensor voltage in the scan data
A digital voltmeter may be used
An oscilloscope may be used

66. Voltmeter Testing Probe between the signal wire and ground
Fast-idle the engine to ensure the sensor is hot
Record the minimum, maximum, and average voltages
The voltage should go below 200 mV, above 800 mV, and average around 450 mV

67. Voltmeter Testing

68. Probe between the signal wire and ground
Oscilloscope Testing
Probe between the signal wire and ground

69. The sensor output should vary as shown
Oscilloscope Testing
The sensor output should vary as shown

70. Zirconia sensor waveform
Oscilloscope Testing
Zirconia sensor waveform

71. If the waveforms are too similar, it indicates a faulty converter
Dual Trace Scope
If the waveforms are too similar, it indicates a faulty converter

72. Emission Systems Wiring

73. O2 Sensor Replacement Disconnect the negative battery cable
Unplug the sensor connector
Spray the threads with penetrating oil
Use a special sensor socket
Inspect for contamination

74. O2 Sensor

75. Lazy sensor contaminated with carbon soot
O2 Sensor
Lazy sensor contaminated with carbon soot

76. Emission Control Information Sticker
The emission control information sticker contains important engine data
evaporative emissions information
schematics
specifications

77. Vehicle Emission Control Information

78. OBD II Drive Cycle Performed:
when the ECM has been disconnected from power
when the diagnostic trouble codes have been erased
to verify repairs, ensuring the DTC does not reoccur
before an emissions test

79. Each vehicle and manufacturer has its own drive cycle
OBD II Drive Cycle
Each vehicle and manufacturer has its own drive cycle

80. OBD II Drive Cycle The vehicle is driven on a road test or dynamometer
To begin, coolant has to be below a specified temperature
The vehicle is driven through various conditions to allow computer to monitor all specified systems