Toyota training course t852 engine control systems sec07

Technician Handbook 874 Engine Control Systems II Evaporative Emissions (EVAP) System Overview The EVAP system’s purpose is to reduce the amount of fuel vapors that the fuel tank and fuel system release into the atmosphere Usually the customer is unaware of an EVAP system issue until the MIL illuminates, as EVAP problems typically not create driveability concerns The customer needs to be aware that they must correctly install the fuel cap after refueling A common EVAP failure is a leak in the system, but restrictions and other failures will also set EVAP related DTCs EVAP Systems Monitoring Regulations require that the EVAP system be monitored for system performance and leak detection Leaks, restrictions, and many components are checked by measuring the pressure of the EVAP system through the Vapor Pressure sensor at various stages of the monitor Early EVAP systems had to detect a 1mm (0.040 inch) hole and greater The system that complies with this regulation is known as the Early Type or Non-Intrusive Beginning with the 2000 model year, regulations required that EVAP systems had to detect a 5mm (0.020 inch) hole and greater This regulation also required vapor purge and component performance to be monitored The first system that met this regulation was the Late Type or Intrusive All EVAP system DTCs are two trip EVAP Systems Technical Training There are a variety of EVAP systems in use with different monitoring strategies It is essential that the EVAP system be correctly identified before beginning diagnosis The best source for identifying the EVAP system on a specific vehicle is the Repair Manual Below is a list of the most common types of EVAP systems: •  Early Type (Non-Intrusive) •  Late Type (Intrusive) •  LEV II •  LEV II with Vacuum Pump (Key-OFF) •  Closed Fuel Tank (hybrid vehicles) 119 Technician Handbook 874 Engine Control Systems II EVAP Diagnosis Tips 1.  It is essential that the EVAP system be correctly identified before beginning diagnosis The best source for identifying the EVAP system on a specific vehicle is the Repair Manual 2.  Set TIS Techstream Vapor Pressure units to mmHg Go to Setup  User Preferences  Unit Selection  Vapor Pressure: mmHg This is to match Repair Manual specifications 3.  Some systems will display Vapor Pressure in two different ways: Absolute and Gauge •  Absolute is the pressure reading based on an atmospheric scale Example: when the system is exposed to atmospheric pressure and the vehicle is at sea level, the Vapor Pressure will be approximately 762 mmHg To use this reading, it is necessary to record the atmospheric pressure when the system is exposed to atmospheric pressure before beginning diagnosis •  Gauge is the pressure reading based on the atmospheric pressure being zero Example: when the system takes a reading of the atmospheric pressure (if applicable), it will set Gauge pressure to zero, and pressures below this will be displayed as negative values (-22 mmHg) 4.  Electrical valves may have to be checked several times and for several seconds in order to diagnose an intermittent failure 5.  To perform an active test, go to the Engine (and ECT) Live Tab  Active Test  then choose the necessary active test Once the active test is entered, create a custom data list by selecting the desired parameters (usually Vapor Pressure Abs and Vapor Pressure Gauge) and clicking the New List button 120 Technical Training Technician Handbook 874 Engine Control Systems II EVAP Diagnosis Tips (cont’d) 6.  A System Check can be performed on some EVAP systems To perform an EVAP System Check, go to Engine (and ECT) Live Tab  Utilities  EVAP System Check 7.  As fuel temperature increases it will increase the pressure in the fuel tank This is why some rise in EVAP system pressure is expected when the system has been exposed to vacuum 8.  The EVAP System Pressure Tester (Essential Tool SST No 00002-6872A) can be used to diagnose the source of an EVAP system leak Always check the EVAP System Pressure Tester for internal leaks by following the procedure on the inside of the tool’s case lid Ask your instructor to demonstrate the use of this tool 9.  The approved smoke tester (Approved Dealer Equipment Catalog Model No ETI2000E) is very effective for diagnosing EVAP system leaks Always follow the directions supplied with this tester The fresh air line is the most effective entry point for the smoke tester; however, VSVs may have to be commanded with active tests to allow the smoke to enter the entire EVAP system Ask your instructor to demonstrate the use and effectiveness of this tool To order this tool, call the Approved Dealer Equipment Catalog phone number at 800-368-6787 10. The EVAP adapter SST number 00002-6872A-ADP3 attaches to the fresh air line at the canister Technical Training 121 Technician Handbook 874 Engine Control Systems II Vapor Pressure Sensor Overview Though there are different styles of vapor pressure sensors, they use the same style circuit The Vapor Pressure Sensor (VPS) measures the vapor pressure in the evaporative emission control system The vapor pressure sensor may be located on the fuel tank, near the charcoal canister assembly or in a remote location This sensor uses a silicon chip with a calibrated reference pressure on one side of the chip The other side of the chip is exposed to vapor pressure Changes in vapor pressure cause the chip to flex and vary the voltage signal to the ECM The voltage signal out depends on the difference between atmospheric pressure and vapor pressure As vapor pressure increases, the voltage signal increases This sensor is sensitive to very small pressure changes (1.0 psi = 51.7 mmHg) Vapor Pressure Sensors come in a variety of configurations When the VPS is mounted directly on the fuel pump assembly, no hoses are required For remote locations, there may be one or two hoses connected to the VPS If the VPS uses one hose, the hose is connected to vapor pressure In the two hose configuration, one hose is connected to vapor pressure, the other hose to atmospheric pressure It is important that these hoses are connected to the proper port If they are reversed, DTCs will set 122 Prepare Vapor Pressure Sensor for EVAP System Diagnosis In some instances, it may be necessary to disconnect hoses from the Vapor Pressure Sensor (tank mounted VPS excluded) prior to test the EVAP system for leaks Be sure to follow Repair Manual or worksheet instructions carefully when preparing the VPS for EVAP system testing Also, ensure that all hoses are reconnected to the VPS correctly after testing or repairing the EVAP system Vapor Pressure Sensor Diagnosis Check all hoses for proper connection, restrictions, and leaks Check the VC and E2 voltages Apply the specified pressure and read sensor voltage output The vapor pressure sensor is calibrated for the pressures found in the EVAP system, so apply only the specified amount to prevent damaging the sensor Check the Freeze Frame data Technical Training Technician Handbook 874 Engine Control Systems II Technical Training 123 Technician Handbook 874 Engine Control Systems II Early Type EVAP System Overview The ECM relies on the vapor pressure (VP) sensor signal to accurately measure pressure in the EVAP system and the purge side of the charcoal canister The changes in the pressures being measured are very small, often 15.5 mmHg (0.3 psi) or less For the VP sensor to measure tank pressure and canister pressure, a threeway VSV is connected to the VP sensor, fuel tank and lines, and charcoal canister When there is no power to the three-way VSV VP sensor, the VP sensor measures canister purge pressure When the ECM turns the VSV ON, the VP sensor measures fuel tank pressure Early Type EVAP System Monitor The ECM tests for leaks by measuring EVAP system pressure in the lines, charcoal canister, and fuel tank When the EVAP pressure is higher or lower than atmospheric pressure, the ECM concludes that no leaks are present EVAP pressure is measured by the VP sensor If either the tank or canister purge side is at atmospheric pressure under specific conditions, the ECM determines there is a leak The leak could be a filler cap not properly tightened, or a hole in the lines, charcoal canister, or fuel tank A visual inspection of the EVAP is performed for most EVAP diagnostic procedures Inspection begins with the filler cap, hoses, and tank Early Type EVAP System Diagnosis Tips 124 The procedure on the next page and the worksheet at the end of this section are meant for training purposes only When trying to determine the cause of an Early Type EVAP system issue, check the Freeze Frame data and duplicate the conditions Use the Technical Information System (TIS) for Repair Manual (RM) and Electrical Wiring Diagram (EWD) information, and look for applicable Service Bulletins (SB) Technical Training Technician Handbook 874 Engine Control Systems II Early Type EVAP System Diagnosis NOTE If multiple codes are displayed, diagnose them in the following order: P0441, P0446, P0440 P0440: Evaporative Emission Control System Malfunction If DTC P0440 is present, the ECM detected atmospheric pressure in the fuel tank side after the vehicle was idling for several minutes, indicating a possible leak on the fuel tank side Using the active test, command the VSV for Vapor Pressure ON/TANK so tank pressure can be monitored and observe the Vapor Pressure parameter If the fuel tank pressure is at atmospheric pressure, there may be a leak on the fuel tank side Inspect the fuel cap and fuel tank side for a leak (brown in the illustration) P0441: Evaporative Emission Control System Incorrect Purge Flow If P0441 is present, the ECM detected vacuum at the charcoal canister when the system was not purging, or a positive pressure at the canister during purge Technical Training 1.  Verify the EVAP purge VSV does not leak when OFF With the engine running, disconnect the electrical connector at the purge VSV Remove the line between the purge VSV and canister Place a finger over the exposed purge valve nipple If vacuum is felt, replace the purge VSV If vacuum is not felt, proceed to step 125 Technician Handbook 874 Engine Control Systems II P0441: Evaporative Emission Control System Incorrect Purge Flow (cont’d) P0446: Evaporative Emission Control System Vent Control Malfunction 2.  Using the active test, turn the purge VSV ON and verify proper duty cycling while monitoring Vapor Pressure (at the canister) Verify that pressure at the canister is well below atmospheric pressure (if atmospheric pressure is 762 mmHg, pressure at the canister during this step should be around 744 mmHg) If pressure does not change when the purge VSV is switched from OFF to ON, check the purge VSV for an inoperative condition, possible electrical malfunction, or a stuck open condition from a foreign object Also, check that the lines to the purge VSV are installed correctly If P0446 is present, the ECM detected atmospheric pressure at the canister after the purge cycle completed, or the pressure of the canister and fuel tank remained the same indicating a problem with the VSV for vapor pressure control (three-way VSV) 1.  Using the active test, turn the purge VSV ON and monitor the Vapor Pressure parameter If the pressure does not drop, the purge VSV may be malfunctioning or the VSV for vapor pressure may be malfunctioning (looking at the tank side pressure only) 2.  If the pressure does drop, turn the purge VSV OFF and watch the canister pressure The pressure should rise slowly, taking approximately one minute for the pressure to rise back to atmospheric 3.  If the pressure rises rapidly, turn the purge VSV ON and use pinch-off pliers to pinpoint the leak on the canister side of the system (yellow in the illustration) 126 Technical Training Technician Handbook 874 Engine Control Systems II Technical Training 127 Technician Handbook 874 Engine Control Systems II Late Type EVAP System Overview The Late Type, also known as Intrusive Type, was developed to meet the very stringent, mandated standard of detecting a 0.5mm (0.020 inch) hole This system uses many of the same components as the Early Type Purge, vacuum relief, pressure relief, and ORVR operations are identical to the Early Type However, the following items have been changed: •  The VP sensor is connected to the tank and is not switched to the canister It is atmospherically referenced (set to 762 mmHg at atmospheric pressure) •  The three-way VSV has been replaced with a bypass VSV which connects the canister and tank during monitor operation •  A closed canister valve (CCV) has been added on the air inlet line allowing the system to be sealed Appendix A illustrates locations of the Late Type EVAP system canister components 128 Technical Training Technician Handbook 874 Engine Control Systems II LEV-II with Vacuum Pump (Key-OFF) EVAP System Monitor The following is a general overview of the LEV-II with Vacuum Pump EVAP system monitor operation: 1.  After all enabling conditions have been met, the ECM turns the canister vent valve OFF and memorizes the atmospheric pressure 2.  The ECM turns the vacuum pump ON, creating negative pressure through the 0.020 inch orifice, and memorizes this as the 0.020 inch leak pressure If no pressure is recorded, the ECM sets DTCs P043E, P043F, and P2401 3.  With the vacuum pump ON, the ECM turns the canister vent valve ON, sealing the system and creating negative pressure in the EVAP system If the stabilized pressure is greater than the 0.020 inch pressure measurement, the ECM determines that the EVAP system has a leak and sets DTC P0455: Evaporative Emission Control System Leak Detected (Gross Leak) or P0456: Evaporative Emission Control System Leak Detected (Very Small Leak) If the pressure goes to atmospheric and remains there through this step, the ECM determines the purge VSV is stuck OPEN and sets DTC P0441: Evaporative Emission Control System Incorrect Purge Flow 4.  The ECM turns the purge VSV ON and the vacuum pump OFF and watches for a sharp rise in pressure If pressure does not rise sharply, the ECM determines that the purge VSV is stuck CLOSED and sets DTC P0441: Evaporative Emission Control System Incorrect Purge Flow Technical Training 145 Technician Handbook 874 Engine Control Systems II LEV-II with Vacuum Pump (Key-OFF) EVAP System Monitor (cont’d) 146 5.  The ECM turns the purge VSV and the canister vent valve OFF and the vacuum pump ON and takes a second 0.020 inch reference pressure measurement 6.  The ECM turns the vacuum pump OFF and takes a second atmospheric pressure measurement NOTE Purge flow is monitored separately when conditions have been met: engine ON, closed loop, ECT above 176 degrees F Both the keyOFF monitor and the purge flow monitor can set DTC P0441: Evaporative Emission Control System Incorrect Purge Flow If DTC P0441 continues to set after clearing DTCs and running the engine (NOT after the automatic system check or key-OFF monitor has run), check for a disconnected, damaged or loose purge line connecting the purge VSV and intake manifold; a restriction in the purge line; or a stuck open or restricted purge VSV NOTE Some LEV-II with Vacuum Pump (Key-OFF) EVAP system monitor strategies will be slightly different Always check the vehicle Repair Manual and NCF information for the correct monitor strategy, component locations, and diagnostic tips and procedures Technical Training Technician Handbook 874 Engine Control Systems II LEV-II with Vacuum Pump EVAP System Diagnosis When trying to determine the cause of a LEV-II with Vacuum Pump EVAP system issue, check the Freeze Frame data and duplicate the conditions Use the Technical Information System (TIS) for Repair Manual (RM) and Electrical Wiring Diagram (EWD) information, and look for applicable Service Bulletins (SB) The LEV II with Vacuum Pump (Key-OFF) EVAP system component locations, by vehicle, can be found in the respective vehicle New Car Features (NCF) manual If the current model year vehicle NCF does not provide EVAP information, access the prior model year’s NCF A manual or automatic EVAP System Check can be performed with the Techstream to aid in diagnosis of this EVAP system To perform an EVAP System Check, go to Engine (and ECT) Live Tab  Utilities  EVAP System Check The illustration shows the graphed Vapor Pressure Gauge parameter of an EVAP System Check snapshot on a known good vehicle Technical Training 147 Technician Handbook 874 Engine Control Systems II 148 Technical Training Technician Handbook 874 Engine Control Systems II Technical Training 149 Technician Handbook 874 Engine Control Systems II 150 Technical Training Technician Handbook 874 Engine Control Systems II Closed Fuel Tank EVAP System Overview On a vehicle equipped with a hybrid system, the hybrid system controls the engine to operate intermittently, making the operation time of the engine shorter than on a normal gasoline engine model Because the engine is unable to sufficiently burn the fuel vapors, the fuel vapor gas that has been created will exceed the capacity of a normal-size canister Therefore, the system releases the fuel vapor gas outside of the fuel tank only when the engine is running and burns it in the engine, in order to comply with the LEV-II-Zero Evap (CARB) and Tier2 (EPA) regulations Due to the closed tank system, the purge flow control and the EVAP leak check have been changed from the LEV-II with Vacuum Pump (Key-OFF) EVAP system Listed below are the construction differences between this system and the LEV-II with Vacuum Pump (Key-OFF) EVAP system: •  A fuel tank close valve (solenoid valve) and a fuel outlet valve (mechanical pressure release valve) have been added between the fuel tank and the canister •  The fuel tank is made of steel •  A fuel lid control switch has been added to the fuel door and is used by the ECM to determine if the fuel door is OPEN or CLOSED •  A second vapor pressure sensor has been added to the fuel tank Technical Training 151 Technician Handbook 874 Engine Control Systems II Closed Fuel Tank EVAP System Monitors Typical enabling conditions necessary for this system’s monitor to run are identical to the LEV-II with Vacuum Pump (Key-OFF) EVAP system and include: •  Five hours have elapsed after the engine has been turned OFF* •  Altitude is below 8,000 feet (2,400 meters) •  Battery voltage is 10.5V or more •  Ignition switch OFF •  ECT between 40 and 95 degrees F (4.4 and 35 degrees C) •  IAT between 40 and 95 degrees F (4.4 and 35 degrees C) *If engine coolant temperature does not drop below 35 degrees C (95 degrees F), this time should be extended to hours Even after that, if the temperature is not less than 35 degrees C (95 degrees F), the time should be extended to 9.5 hours The Closed Fuel Tank EVAP system will perform two different leak monitors based on the fuel tank internal pressure: 1.  If the fuel tank internal pressure is higher or lower than the atmospheric pressure, the ECM determines there are no leaks in the fuel tank and will not check it for leaks 2.  If the fuel tank internal pressure is near atmospheric pressure, the ECM will check it for leaks 152 Technical Training Technician Handbook 874 Engine Control Systems II Fuel Tank Internal Pressure Higher or Lower Than Atmospheric The following is a general overview of the Closed Fuel Tank EVAP system monitor operation when fuel tank internal pressure is higher or lower than atmospheric pressure (this condition tells the ECM, without further testing, that the fuel tank is not leaking): 1.  After all enabling conditions have been met, the ECM turns the canister vent valve OFF (vent to atmosphere) and memorizes the atmospheric pressure 2.  The ECM turns the vacuum pump ON, creating negative pressure through the 0.020 inch orifice, and memorizes this as the 0.020 inch leak pressure If the pressure is below specification, the ECM sets DTC P043E; if above specification, the ECM sets DTCs P043F, P2401, and P2402 3.  With the vacuum pump ON, the ECM turns the canister vent valve ON, sealing the system and creating negative pressure in the EVAP system If the stabilized pressure is greater than the 0.020 inch pressure measurement, the ECM determines that the EVAP system has a leak and sets DTC P1421: (gross leak) or P1420: (very small leak) 4.  The ECM turns the purge VSV ON and watches for a sharp rise in pressure If pressure does not rise sharply, the ECM determines that the purge VSV is stuck CLOSED and sets DTC P0441: Evaporative Emission Control System Incorrect Purge Flow Technical Training 153 Technician Handbook 874 Engine Control Systems II Fuel Tank Internal Pressure Higher or Lower Than Atmospheric 5.  The ECM turns the canister vent valve OFF (vent to atmosphere) and takes a second 0.020 inch leak pressure measurement Next, the ECM turns the vacuum pump OFF and takes a second atmospheric pressure measurement The ECM turns the canister vent valve OFF 6.  The ECM turns the fuel tank close valve ON, releasing negative or positive pressure from the fuel tank into the canister side of the EVAP system If pressure in the canister does not change (become closer to fuel tank pressure), the ECM determines that the fuel tank close valve is stuck CLOSED and sets DTC P2451 7.  The ECM turn the vacuum pump OFF and takes a final atmospheric pressure measurement NOTE 154 The Purge Flow Control is also monitored for malfunctions Technical Training Technician Handbook 874 Engine Control Systems II Fuel Tank Internal Pressure Same As Atmospheric The following is a general overview of the Closed Fuel Tank EVAP system monitor operation when fuel tank internal pressure is the same as atmospheric pressure (process includes fuel tank leak test): 1.  After all enabling conditions have been met, the ECM turns the canister vent valve OFF (vent to atmosphere) and memorizes the atmospheric pressure 2.  The ECM turns the vacuum pump ON, creating negative pressure through the 0.020 inch orifice, and memorizes this as the 0.020 inch leak pressure If the pressure is below specification, the ECM sets DTC P043E; if above specification, the ECM sets DTCs P043F, P2401, and P2402 3.  With the vacuum pump ON, the ECM turns the canister vent valve ON, sealing the system and creating negative pressure in the EVAP system If the stabilized pressure is greater than the 0.020 inch pressure measurement, the ECM determines that the EVAP system has a leak and sets DTC P1421 (gross leak) or P1420 (very small leak) If the fuel tank pressure fluctuates during this step, the ECM determines that the fuel tank close valve is stuck OPEN and sets DTC P2450 4.  The ECM turns the purge VSV ON and watches for a sharp rise in pressure If pressure does not rise sharply, the ECM determines that the purge VSV is stuck CLOSED and sets DTC P0441 Technical Training 155 Technician Handbook 874 Engine Control Systems II Fuel Tank Internal Pressure Same As Atmospheric (cont’d) 5.  The ECM turns the canister vent valve OFF (vent to atmosphere) and takes a second 0.020 inch leak pressure measurement Next, the ECM turns the vacuum pump OFF and takes a second atmospheric pressure measurement 6.  The ECM turns the vacuum pump ON, opens the fuel tank close valve (ON), and closes the canister vent valve to create negative pressure in the fuel tank If the stabilized pressure is greater than the 0.020 inch pressure measurement, the ECM determines that the fuel tank has a leak and sets P1422 (Fuel Tank Small Leak) or DTC P1423 (Fuel Tank Gross Leak) If fuel tank pressure does not change during this step, the ECM determines that the fuel tank close valve is stuck CLOSED and sets DTC P2451 7.  The ECM turns the canister vent valve OFF (open), closes the fuel tank close valve, and takes a final 0.020 inch reference pressure measurement 8.  The ECM turns the vacuum pump OFF and takes a final atmospheric pressure measurement NOTE 156 The Purge Flow Control is also monitored for malfunctions Technical Training Technician Handbook 874 Engine Control Systems II Closed Fuel Tank EVAP System Diagnosis When trying to determine the cause of a Closed Fuel Tank EVAP system issue, check the Freeze Frame data and duplicate the conditions Use the Technical Information System (TIS) for Repair Manual (RM) and Electrical Wiring Diagram (EWD) information, and look for applicable Service Bulletins (SB) The Closed Fuel Tank EVAP system component locations, by vehicle, can be found in the respective vehicle New Car Features (NCF) manual If the current model year vehicle NCF does not provide EVAP information, access the prior model year’s NCF A manual or automatic EVAP System Check can be performed with the Techstream to aid in diagnosis of this EVAP system To perform an EVAP System Check, go to Engine (and ECT) Live Tab  Utilities  EVAP System Check If DTC(s) related to the tank side only or canister side only are present, check those parts of the system first If a leak on the tank side is present, check for a leaking or loose fuel cap first The diagnostic procedures in the LEV-II with Vacuum Pump (Key-OFF) EVAP System Diagnosis portion of this section can also be used to diagnose issues with the Closed Fuel Tank EVAP system Technical Training 157 Technician Handbook 874 Engine Control Systems II 158 Technical Training Technician Handbook 874 Engine Control Systems II Technical Training 159 ... good vehicle Technical Training 147 Technician Handbook 874 Engine Control Systems II 148 Technical Training Technician Handbook 874 Engine Control Systems II Technical Training 149 ... in the illustration) 126 Technical Training Technician Handbook 874 Engine Control Systems II Technical Training 127 Technician Handbook 874 Engine Control Systems II Late Type EVAP System Overview... EVAP Tester or Smoke Tester Technical Training Technician Handbook 874 Engine Control Systems II Technical Training 137 Technician Handbook 874 Engine Control Systems II LEV-II EVAP System Overview