Interpret diagnostic trouble codes (DTCs) and scan tool data related to the emissions control systems; determine necessary action.
Lesson Plan for
AUT 188-189/AUT 293
Automotive Service Technology Section D/Automotive Special Problems
Course HS Title: / Automobile Service Technology/Special Problems / Program:KCTCS Courses included in HS Title: (Lesson is prepared for course highlighted.)
KCTCS Course No. / KCTCS Course Title
Introduction/Context / This lesson will instruct the student on how to interpret diagnostic trouble codes (DTCs) and scan tool data related to the emissions control systems, and determine necessary action. Knowledge of these techniques and the skills required to correct problems associated with this task are necessary for a student to acquire if they wish to compete for high paying, high skilled jobs in an Automotive Repair Facility. Entry level technicians need to be able to perform this task to 100% accuracy. Incorrectly performing this task can lead to an automobile accident or create customer satisfaction issues.
Prepared By / School / Date:
Grade Level / No. Students / No.IEP's: / Lesson Length:
Task
Interpret diagnostic trouble codes (DTCs) and scan tool data related to the emissions control systems; determine necessary action.
No. / Objective
1 / Given the proper tools and instruction, the student will be able to interpret diagnostic trouble codes (DTCs) and scan tool data related to the emissions control systems, determine necessary action, and pass a written test covering the task with 100% accuracy.
Connections:
Skills Standards:OH 001
OH 002
OH 003
OD 002
OD 003
OD 005
Common Core Technical Standards:
TD-SYS-2
New Common Core Standards:
RST 11-12.2
RST 11-12 3
A-CED-4
N-Q-1
New Generation Science Standards:
HS-PS2-5.
HS-PS3-3.
HS-PS3-5.
INSTRUCTIONAL MATERIALS/TECHNOLOGY
Teacher Designed Materials and Other Handouts
Textbooks and Workbooks
Ken Pickerill / Automotive Engine Performance / Fourth / Delmar / 635-636
Tim Gilles / Automotive Service Inspection, Maintenance and Repair / Third / Delmar / 691-693
Web Addresses
Testing Evaporation Control Systems / Auto Inc. / http://www.asashop.org/autoinc/sept97/techtotech.htm
Today's Class / Melior / www.todaysclass.com
Equipment
As Needed / Scan Tool / Various
Content/Presentation/Demonstration Outline
Inform students to be sure all the conditions required to energize the purge solenoid are present, and observe this solenoid status on the scan tester. The tester should indicate the purge solenoid is on when all the conditions are present for canister purge operation. Explain that if the purge solenoid is not on under the necessary conditions, be sure to check the power supply wire to the solenoid, solenoid winding, and the wire from the solenoid to the PCM. The PCM can control the purge and vent valves open and closed. When used in conjunction with the tank pressure sensor, this enables diagnostics on the integrity of the system.
Describe the initial vacuum pull down, or the weak vacuum test to students. Explain that this will establish if there is a large system leak. Tell students that once the enable criterion (on the scan tool) is set, the PCM will close the vent valve and open the purge valve. This would cause a vacuum to be indicated on the fuel tank pressure sensor if the system were sealed. Let students know that if the vehicle should fail to pull a vacuum of up to 7 in. Hg, then the MIL would illuminate after the second consecutive failure under similar conditions and set a code P0455, gross evaporative system leak.
Tell students that some vehicles will set a "Check Fuel Cap" light and a code P0457 after this test was failed after a refueling event was detected by the PCM using the fuel level sensor. Explain that one of the problems associated with the evaporative emissions were customers who failed to install their fuel cap tight enough for a good seal, which alerts the PCM to a problem. Some other problems that may be indicated by this failure are a large system leak, such as a vapor line loose or kinked, or a hole in the system. Another would be a stuck-open vent solenoid, or loose vent line (basically the PCM cannot close the valve).
Inform students that if the initial vacuum pull down (weak vacuum test) passes, the system assumes there is no large leak, and begins to check for a small leak. Tell students that this is done through the vacuum hold and decay, or small leak test. For this test, explain that the system will look for a leak that is down to 0.020 inch in size. The vent and purge solenoids will close and the PCM will watch for decay in the vacuum being held. Tell students that if the vacuum drops too quickly, a P0442 is armed and set if the system fails again under similar conditions.
Explain to students that with leaks so small, the software in the PCM makes allowance for the buildup of pressure inside the tank due to high volatility fuel, and/or high ambient temperatures and excessive fuel slosh. For these reasons, tell students that the test will abort if fuel level, engine load, or fuel tank pressure should change abruptly. The pressure from high volatility fuel could reduce the vacuum measured and result in false code triggering.
Inform students that in order to guard against this false triggering, the vent can be opened, eliminating the vacuum entirely, and then the system vent and purge valves can be closed while the PCM actually measures how much pressure is being added to the tank by the fuel volatility. Instruct students that the cold idle test can be used to entirely screen out the effects of fuel volatility by running the test only with the fuel cold (engine running less than 10 minutes) and the vehicle at idle or less than 10 mph. Tell students that even this test can be cancelled by conditions that may produce excessive fuel slosh conditions.
Let students know that the sealing of the purge valve is checked by measuring vacuum inside the tank with the vent and purge valve closed. If there is vacuum building under these conditions it is assumed that the purge valve is leaking. Tell students this will set a code P1443 on Ford vehicles.
Instruct students on the Engine Off Natural Vacuum (EONV) test. Explain that the system runs a pressure and vacuum test based on the natural volatility of the fuel. Inform students that after driving, the fuel will be warm, and if the vent to the tank is closed, the fuel pressure will build according to the ambient temperature. Let students know that after the fuel starts to cool down, again with the vent closed, there will be a natural vacuum build within the tank that the system can measure. The PCM can use this information to determine if there are any small leaks in the system. If the fuel is too volatile, as determined by the rise in pressure after the engine is turned off, the test is cancelled. Tell students that this test is also a small leak test setting P0442 if failed.
Applications/Practice
Evaluation and feedback Prior to Testing or Lab Work
STUDENT ASSESSMENT:(Assess student progress with performance criteria.)
IMPACT--Reflection/Analysis of Teaching and Learning: (How did students’ progress in relation to the state objectives? Was the instruction successful? Analyze samples of student work particularly that which is unsatisfactory, for the purpose of planning further instruction.)
REFINEMENT--Lesson Extension and Follow-up: (To be filled in as the lesson is modified during initial planning and/or during the teaching learning process.)