Toyota training course t852 engine control systems sec08

Technician Handbook 874 Engine Control Systems II Single Pump Secondary Air Injection System Overview On some models with a V8 engine, during cold engine start, air injection is turned ON and adds fresh air to the exhaust stream to help speed catalyst warm-up Under specified operating conditions, the ECM signals the air injection driver to turn ON the electric pump The pump draws ambient air in through a filter and pressurizes it Two different air switching valves control whether the fresh air reaches the injection tube in the engine exhaust port •  Air switching valve No is a solenoid valve controlled by the ECM through the air injection driver •  Air switching valve No is a 2-part vacuum valve directly controlled by the ECM — each half sends air to one bank of a V-type engine The pressure sensor allows the ECM to measure pump output In addition, if measured pressure is pulsating, this indicates both air switching valves are open and the pressure sensor is exposed to exhaust gas 160 Single Pump Secondary Air Injection Monitor The ECM uses the pressure sensor signal to monitor the valve positions and pump operation The ECM uses the air injector driver (AID) to monitor the pressure sensor circuit, valve circuits, and pump circuit Air Injection DTCs may be one trip or two trip, depending on the type Single Pump Secondary Air Injection DTCs The ECM checks for malfunctions in valve positions, pump operation, driver operation, and circuits Refer to the Repair Manual (RM) for specific DTC and monitor information Technical Training Technician Handbook 874 Engine Control Systems II Single Pump Secondary Air Injection System Monitor Sequence The ECM detects pressure change with the pressure sensor to determine malfunctioning parts in the system and stores the DTCs At points A through F: •  The ECM measures pressure and/or exhaust pulsation of the system •  When the pressure is high, the ECM determines that the pump operates •  When exhaust pulsation is detected, the ECM determines that the Air Switching Valve (ASV) is open •  The ECM determines malfunctioning parts based on the measured pressure sensor value, and stores the appropriate DTCs At points A and B: •  The ECM detects pressure changes (decrease), and determines that the No Air Switching Valves are opening At points C and F: •  The ECM detects pressure and exhaust pulsation, and determines the pressure pattern of the system At point D: •  The ECM operates the system, as indicated by the dashed lines, to determine which of the No ASV are malfunctioning only when pressure changes cannot be detected at point A or B At point E: •  The ECM looks for exhaust pulsation to determine the condition of the system At point F: •  The ECM opens the ASV (electromagnetic type) and looks for exhaust pulsations If exhaust pulsations are present, the ECM concludes that one or both of the No ASVs are stuck open and sets the appropriate DTC(s) Refer to the Repair Manual for more information on the Air Injection monitor sequence, enabling conditions, and judgment of failure conditions Technical Training 161 Technician Handbook 874 Engine Control Systems II Single Pump Secondary Air Injection System Diagnosis When trying to determine the cause of a single pump secondary air injection 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) Also, use the RM for component locations on the vehicle you are working with The single pump secondary air injection driver sends different dutycycle signals to the ECM based on air injection system operating conditions The duty-cycle signal can be displayed on an oscilloscope while performing air injection active tests with the Techstream One or more different duty-cycle signals may result in a single DTC being set, so knowing the exact duty-cycle signal will help pinpoint the problem area A manual or automatic Air Injection Check can be performed with the Techstream to aid in diagnosis of this system To perform an Air Injection Check, go to Engine (and ECT) Live Tab  Utilities  Air Injection Check An Activate the VSV for Secondary Air Control active test can also be performed to aid in diagnosis of this system 162 NOTE The system checks allow technicians to operate the AI system for only seconds Furthermore, the test can be performed times per trip If the test is repeated, intervals of at least 30 seconds are required between tests Single Pump Secondary Air Injection System Diagnosis Tips The air pressure readings, air/fuel ratio (A/F Bank) (Manual System Check only) and AFS voltage readings (Active Test only) of Bank and Bank are good indicators of system performance Technical Training Technician Handbook 874 Engine Control Systems II Technical Training 163 Technician Handbook 874 Engine Control Systems II Dual Pump Secondary Air Injection System Overview For this system, Bank and Bank each have an electric air pump, air injection control driver, air injection control valve, and air pressure sensor Control of B1 and B2 secondary air injection system is performed independently Two pumps are used to increase the amount of air supplied, shortening the catalyst warmup time The ECM estimates the amount of air injected to the TWCs based on signals from the mass air flow meter in order to regulate the air injection time Air is injected under the following conditions: •  Engine Coolant Temperature: 41 to 113°F (5 to 45°C) •  Intake Air Temperature: 41°F (5°C) or more 164 Technical Training Technician Handbook 874 Engine Control Systems II Dual Pump Secondary Air Injection Monitor The ECM uses the pressure sensor signal to monitor the valve positions and pump operation The ECM uses the air injector driver (AID) to monitor the pressure sensor circuit, valve circuits, and pump circuit Air Injection DTCs may be one trip or two trip, depending on the type The ECM detects operation of the air injection system based on signals from the air pressure sensor as follows: 1.  When the electric air pump is ON and the air injection control valve is closed, the pressure is high and stable 2.  When the electric air pump is ON and the air injection control valve is open, the pressure drops slightly and becomes unstable because of exhaust pulses 3.  When the electric air pump is OFF and the air injection control valve is closed, the pressure remains at zero 4.  When the electric air pump is OFF and air injection control valve is open, the pressure drops below zero and becomes unstable because of exhaust pulses Dual Pump Secondary Air Injection DTCs Technical Training The ECM checks for malfunctions in valve positions, pump operation, driver operation, and circuits Refer to the Repair Manual (RM) for specific DTC and monitor information 165 Technician Handbook 874 Engine Control Systems II Dual Pump Secondary Air Injection System Diagnosis When trying to determine the cause of a dual pump secondary air injection 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) Also, use the RM for component locations on the vehicle you are working with The dual pump secondary air injection drivers send different dutycycle signals to the ECM based on air injection system operating conditions The duty-cycle signal can be displayed on an oscilloscope while performing air injection active tests with the Techstream One or more different duty-cycle signals may result in a single DTC being set, so knowing the exact duty-cycle signal will help pinpoint the problem area A manual or automatic Air Injection Check can be performed with the Techstream to aid in diagnosis of this system To perform an Air Injection Check, go to Engine (and ECT) Live Tab  Utilities  Air Injection Check An Activate the VSV for Secondary Air Control active test can also be performed to aid in diagnosis of this system 166 NOTE The system checks allow technicians to operate the AI system for only seconds Furthermore, the test can be performed times per trip If the test is repeated, intervals of at least 30 seconds are required between tests Dual Pump Secondary Air Injection System Diagnosis Tips The air pressure readings, air fuel ratio (A/F Bank) (Manual System Check only) and AFS voltage readings (Active Test only) of Bank and Bank are good indicators of system performance Pulsation information indicates if the air injection control valves are functioning Technical Training Technician Handbook 874 Engine Control Systems II Technical Training 167 Technician Handbook 874 Engine Control Systems II 168 Technical Training ... injection control valves are functioning Technical Training Technician Handbook 874 Engine Control Systems II Technical Training 167 Technician Handbook 874 Engine Control Systems II 168 Technical Training. .. indicators of system performance Technical Training Technician Handbook 874 Engine Control Systems II Technical Training 163 Technician Handbook 874 Engine Control Systems II Dual Pump Secondary Air... conditions: •  Engine Coolant Temperature: 41 to 113°F (5 to 45°C) •  Intake Air Temperature: 41°F (5°C) or more 164 Technical Training Technician Handbook 874 Engine Control Systems II Dual