874 Engine Control Systems II Technician Handbook Single Pump Secondary Air Injection System Overview On some models with a V8 engine, during cold engine start, air injection is tur
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Technician Handbook
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 1 is a solenoid valve controlled by the ECM through the air injection driver
• Air switching valve No 2 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
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 checks for malfunctions in valve positions, pump operation, driver operation, and circuits Refer to the Repair Manual (RM) for specific DTC and monitor information
Single Pump Secondary Air Injection Monitor
Single Pump Secondary Air Injection DTCs
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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 2 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 2 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 2 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
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Technician Handbook
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 duty-cycle 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
The system checks allow technicians to operate the AI system for only 5 seconds Furthermore, the test can be performed 4 times per trip If the test is repeated, intervals of at least 30 seconds are required between tests
The air pressure readings, air/fuel ratio (A/F Bank) (Manual System Check only) and AFS voltage readings (Active Test only) of Bank 1 and Bank 2 are good indicators of system performance
Single Pump Secondary Air Injection System
Diagnosis Tips
NOTE
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Dual Pump Secondary Air
Injection System
Overview
For this system, Bank 1 and Bank 2 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
warm-up 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
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Technician Handbook
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
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
Dual Pump Secondary Air
Injection DTCs
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Technician Handbook
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 duty-cycle 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
The system checks allow technicians to operate the AI system for only 5 seconds Furthermore, the test can be performed 4 times per trip If the test is repeated, intervals of at least 30 seconds are required between tests
The air pressure readings, air fuel ratio (A/F Bank) (Manual System
Check only) and AFS voltage readings (Active Test only) of Bank 1 and Bank 2 are good indicators of system performance
Pulsation information indicates if the air injection control valves are functioning
NOTE
Dual Pump Secondary Air Injection System
Diagnosis Tips
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