start Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 62, the reader should be able to: • • • • Prepare for the ASE Engine Performance (A8) certification test content area “D” (Emission Control Systems) Describe the purpose and function of the exhaust gas recirculation system Explain methods for diagnosing and testing for faults in the exhaust gas recirculation system Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 62, the reader should be able to: • Describe the purpose and function of the • • • positive crankcase ventilation and the air injection reaction system Explain methods for diagnosing and testing faults in the PCV and AIR systems Describe the purpose and function of the catalytic converter Explain the method for diagnosing and testing the catalytic converter Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 62, the reader should be able to: • Describe the purpose and function of the • • evaporative emission control system Discuss how the evaporative emission control system is tested under OBD-II regulations Explain methods for diagnosing and testing faults in the evaporative emission control system Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: adsorption • air injection reaction (AIR) backpressure • blowby canister purge (CANP) • catalyst • catalytic converter • cerium • check valves delta pressure feedback EGR (DPFE) • digital EGR evaporative control system • EGR valve position (EVP) • electronic vacuum regulator valve (EVRV) • exhaust gas recirculation (EGR) heated oxygen sensor (HO2S) Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: inert • infrared pyrometer leak detection pump (LDP) • light-off • light-off converter (LOC) • linear EGR mini-converter negative backpressure • nitrogen oxides (NOX) oxygen storage capacity (OSC) palladium • platinum • positive backpressure • positive crankcase ventilation (PCV) • pressure feedback EGR (PFE) • preconverter • pup converter Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: rhodium smog pump thermactor pump • three-way catalytic converter (TWC) washcoat Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SMOG The common term used to describe air pollution is smog, a word  that combines the two words smoke and fog. Smog is formed in the  atmosphere when sunlight combines with unburned fuel  (hydrocarbon, or HC) and oxides of nitrogen (NOX) produced  during combustion.  NOTE: Although upper­atmospheric ozone is desirable because it blocks out harmful ultraviolet rays from the sun, ground­level ozone is considered  to be unhealthy smog HC (unburned hydrocarbons)  Excessive HC emissions  (unburned fuel) are controlled by the evaporative system  (charcoal canister), the positive crankcase ventilation (PCV)  system, the air­pump system, and the catalytic converter Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 NOX (oxides of nitrogen)  Excessive NOX emissions are controlled by the exhaust gas  recirculation (EGR) system and catalytic converter. An oxide of nitrogen (NO) is a  colorless, tasteless, and odorless gas, but as soon as it reaches the atmosphere and mixes  with more oxygen, nitrogen oxides (NO 2) are formed, which appear as reddish­brown CO (carbon monoxide) Excessive CO emissions are controlled by the PCV system, the air­ pump system, and  catalytic converter Figure 62–1 Notice the reddish-brown haze that is often over many major cities Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 EXHAUST GAS RECIRCULATION SYSTEMS Exhaust gas recirculation (EGR) is emission control that lowers  nitrogen oxides (NOX). In the presence of sunlight, NO X reacts  with hydrocarbons in the atmosphere to form ozone (O 3) or  photochemical smog, an air pollutant NOX Formation  Nitrogen N2 and oxygen O2 molecules are  separated into individual atoms of nitrogen and oxygen during  combustion. These then bond to form NO X (NO, NO2) When combustion flame­front temperatures exceed 2500°F  (1370°C), NOX formation increases dramatically Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 EVAPORATIVE SYSTEM MONITOR OBD­II computer programs not only detect faults, but also  periodically test various systems and alert the driver before  emissions­related components are harmed by system faults Serious faults cause a blinking malfunction indicator lamp (MIL)  or even an engine shutdown; less serious faults may simply store a  code but not illuminate the MIL The OBD­II requirements state that vehicle fuel systems are to be  routinely tested while underway by the PCM management system Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 All OBD­II vehicles—during normal driving cycles and under  specific conditions—experience a canister purge system pressure  test, as commanded by the PCM. While the vehicle is being driven,  the vapor line between the canister and the purge valve is  monitored for pressure changes.  The EVAP system monitor tests for purge volume and leaks. Most  applications purge the charcoal canister by venting the vapors into  the intake manifold during cruise. To do this, the PCM typically  opens a solenoid­operated purge valve installed in the purge line  leading to the intake manifold A typical EVAP monitor first closes off the system to atmospheric  pressure and opens the purge valve during cruise operation. A fuel  tank pressure (FTP) sensor then monitors the rate with which  vacuum increases in the system.  Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 The monitor uses this information to determine the purge volume  flow rate. To test for leaks, the EVAP monitor closes the purge valve,  creating a completely closed system. The fuel tank pressure sensor  then monitors the leak down rate.  Figure 62–35 The fuel tank pressure sensor (black unit with three wires) looks like a MAP sensor and is usually located on top of the fuel pump module (white unit) If the rate exceeds PCM­stored  values, a leak greater than or  equal to the OBD­II standard of  0.040 in. (1.0 mm) or 0.020 in.  (0.5 mm) exists.  The fuel tank pressure sensor is often the same part as the MAP  sensor, and instead of monitoring intake manifold absolute pressure,  it is used to monitor fuel tank pressure.  Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Engine Off Natural Vacuum  System integrity (leakage) can  also be checked after the engine is shut off The premise is that a warm evaporative system will cooldown  after the engine is shut off and the vehicle is stable. A slight  vacuum will be created in the gas tank during this cooldown  period. If a specific level of vacuum is reached and maintained,  the system is said to have integrity (no leakage) Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Tighten the Cap Correctly Many diagnostic trouble codes (DTCs) are set because the gas cap has not been properly installed Many diagnostic trouble codes (DTCs) are set because the gas cap has not been properly installed To be sure a screw-type gas cap is properly sealed, tighten the cap until it clicks three times The clicking is a ratchet device and the clicking does not harm the cap Therefore, if a P0440 or similar DTC is set, check the cap Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman Figure 62–36 This Toyota cap has a warning, the check engine light will come on if not tightened until one click ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 TYPICAL EVAP MONITOR The PCM will run the EVAP monitor when the following enable  criteria are met. Typical enable criteria include: Cold start BARO greater than 70 kPa (20.7 in. Hg or 10.2 psi) IAT between 39° and 86°F at engine start­up ECT between 39° and 86°F at engine start­up ECT and IAT within 39°F of each other at engine start­up Fuel level within 15% to 85% TP sensor between 9% and 35% Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Running the EVAP Monitor  There are four tests which are performed during a typical  GM EVAP monitor A DTC is assigned to each test Weak Vacuum Test (P0440—large leak)  Identifies gross  leaks. During the monitor, the vent solenoid is closed and the  purge solenoid is duty cycled. The FTP should indicate a  vacuum of approximately 6 to 10 in. H2O Small Leak Test (P0442—small leak)  After the large leak  test passes, the PCM checks for a small leak by keeping the  vent solenoid closed and closing the purge solenoid. The  system is now sealed. PCM measures change in FTP voltage  over time Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Excess Vacuum Test (P0446)  Vent path restrictions. With  the vent solenoid open and purge commanded, PCM should  not see excessive vacuum in the EVAP system. Typical  EVAP system vacuum with the vent solenoid open is about 5 to 6 in. H2O Purge Solenoid Leak Test (P1442)  With the purge solenoid  closed and vent solenoid closed, no vacuum should be present  in the system. If there is vacuum present, the purge solenoid  may be leaking Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Keep the Fuel Tank Properly Filled Most evaporative system monitors will not run unless the fuel level is between 15% and 85% In other words, if a driver always runs with close to an empty tank or always tries to keep the tank full, the EVAP monitor may not run Figure 62–37 The fuel level must be above 15% and below 85% before the EVAP Monitor will run on most vehicles Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 See the chart on Page 761 of your textbook.  Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY Recirculating 6% to 10% inert exhaust gases back into the intake  system reduces peak temperature inside the combustion chamber  and reduces NOX exhaust emissions EGR is usually not needed at idle, at wide­open throttle, or when  the engine is cold Many EGR systems use a feedback potentiometer to signal the  PCM the position of the EGR valve pintle OBD­II regulation requires that the flow rate be tested and then is  achieved by opening the EGR valve and observing the reaction of  the MAP sensor Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY (cont.) Positive crankcase ventilation (PCV) systems use a valve or a  fixed orifice to transfer and control the fumes from the  crankcase back into the intake system A PCV valve regulates the flow of fumes depending on engine  vacuum and seals the crankcase vent in the event of a backfire As much as 30% of the air needed by the engine at idle speed  flows through the PCV system The AIR system forces air at low pressure into the exhaust to  reduce CO and HC exhaust emissions Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY (cont.) A catalytic converter is an after­treatment device that reduces  exhaust emissions outside of the engine. A catalyst is an  element that starts a chemical reaction but is not consumed in  the process 10 The catalyst material used in a catalytic converter includes  rhodium, palladium, and platinum 11 The OBD­II system monitor compares the relative activity of a  rear oxygen sensor to the precatalytic oxygen sensor to  determine catalytic converter efficiency Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY (cont.) 12 The purpose of the evaporative emission (EVAP) control  system is to reduce the release of volatile organic compounds  (VOCs) into the atmosphere 13 A carbon (charcoal) canister is used to trap and hold gasoline  vapors until they can be purged and run into the engine to be  burned 14 OBD­II regulation requires the evaporative emission control  system be checked for leakage and proper purge flow rates 15 External leaks can best be located by pressurizing the fuel  system with low­pressure smoke Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 end Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458