Automobili Lamborghini s.p.a. OBDII MY 07 Section 5 Page 1 SECONDARY AIR SYSTEM (SAIR) MONITORING

Transcription

1 Automobili Lamborghini s.p.a. OBDII MY 07 Section 5 Page 1 SECONDARY AIR SYSTEM (SAIR) MONITORING

2 Automobili Lamborghini s.p.a. OBDII MY 07 Section 5 Page Basic theory and algorithm

3 Automobili Lamborghini s.p.a. OBDII MY 07 Section 5 Page 3 The Secondary Air System (SAIR) controls the injection of additional external air into the engine, close to the exhaust valve seats. This is active only for the first seconds of the engine cold start, during the warm-up: in this period the catalyst has not reached yet its operating temperature. This System reduce the level of hydrocarbon emissions (HC) which are emitted untreated (unburned gases). The post oxidation of these unburned gases by the secondary air injection also has the effect of heating up the catalyst quickly. This phenomena improves the catalyst light-off. Therefore, the task of the secondary air system strategy is to both oxidize HC and simultaneously warm up the catalytic converter. The secondary air injection causes a very lean mixture in the exhaust gases due to the excess of air. Therefore, the response of the front UEGO sensor and of the rear O2 sensor is leaner when the secondary air system is active. According to the section (e) (5.2.3) of the Malfunction and Diagnostic System Requirements and Subsequent Model-Year Passenger Cars, Light-Duty Trucks, and Medium-Duty Vehicles and Engines a test is performed during the "normal operation, that is within the first seconds following the engine start, using the signal of the rear O2 Sensor when the Air Pump is energized. See chapter for the details about this diagnosis. An additional strategy with an intrusive test checks the exact air flow delivered to the exhaust system according to the paragraph (e) (5.2.1) using the front UEGO Sensor output (Ip current) by a comparison of the Integral of the two sensors Ip to a threshold value.. See chapter for the details about this diagnosis. In addition to these diagnosis it is monitored also the electro valve with a feedback test in accordance with the comprehensive component requirements, as specified in paragraph (e)-(5.1).see chapter 16.1 for the details about this diagnosis. For diagnosis constants see OBDII MALFUNCTION CRITERIA CHART.

4 Automobili Lamborghini s.p.a. OBDII MY 07 Section 5 Page 4 Below is the schematic of the SAIR layout, identical for both cars L140 and L147, both the layout and the components. The ECM drives the electronic valve by its duty cycle, which opens the two pneumatic valves, one for each bank, by vacuum. Also, the ECM is electrically connected to the air pump through a relay, which blows the air through the pneumatic valves to the engine head at the exhaust valve seats LAYOUT SECONDARY AIR SYSTEM ECU Electro valve Va cu um Pneumatic valve Pneumatic valve Engine head Engine head REL AY Air pump

5 Automobili Lamborghini s.p.a. OBDII MY 07 Section 5 Page 5 MONITORING DURING NORMAL OPERATION During the monitoring performed in the normal operation of the secondary air strategy the engine runs while the fuel system is in open loop with a rich Air/Fuel ratio mixture, approximately with lambda 0.97, while the Air/Fuel ratio present in the exhaust is lean do to the additional air delivered by the pump, approximately lambda The Air/fuel ratio in the exhaust is lean enough to guarantee a signal of the rear O2 sensor lean (< 0,4V) when the system works properly, and is rich enough to guarantee a rich signal (> 0,4V) when some problem occurs in the system. The monitoring during the normal operation is performed by the rear O2 sensor under the following conditions: Air pump energized and electronic valve activated Engine running Rear O2 sensor active (fully warmed up) Nominal Airflow through the engine < threshold The condition on the nominal airflow through the engine is necessary because the flow from the pump must be significant against the flow from the engine. When these conditions are verified the system checks that the rears O2 signal goes to the lean position within a calibrated time and that remains lean for a minimum calibrated time. If this do not occurs, the pending fault is stored in the ECM.

6 Automobili Lamborghini s.p.a. OBDII MY 07 Section 5 Page 6 INTRUSIVE TEST FOR THE MONITORING OF THE AIRFLOW Since the SAIR diagnostic uses the front UEGO sensor, this diagnostic is operated only after the front UEGO sensor diagnostic is completed (Response Rate test ended). With the signal of the UEGO sensor practically it is measured the air flow present in the exhaust. The monitoring is performed in 4 main steps, identified by the flag AS_DG_Status (see the SAIR diagnosis FLOW CHART). Step 1: AS_DG_Status = 1 In the first step the conditions for diagnosis are verified (see the SAIR diagnostic conditions FLOW CHART). After the front UEGO sensor control is set in open loop, the front UEGO sensor control in open loop permits the evaluation of the effects provided by the secondary air injection. The diagnostic is performed at idle conditions. Conditions for diagnosis: - No OBD faults First the status of the following diagnostic which are related to the SAS SAIR diagnostic. That is the diagnostic can be operated only if the other components do not show major defects which can affect the SAIR monitoring. - Front UEGO sensor OK - Misfire OK - Fuel system OK - Drive By Wire OK - Engine coolant temperature H2O (TH2O) at cranking (TH2Oavv) above a threshold - Current engine coolant temperature (TH2O) above a threshold - Front UEGO sensor control in Closed Loop - Front UEGO sensor control correction (LambdaTarget) between thresholds minimum and maximum - Front UEGO sensor Response Rate Diagnostic ended - Engine at Idle conditions Note that the SAIR monitoring is conducted after the conclusion of the front UEGO sensor Response Rate diagnostic for two reasons: To be sure that the SAIR monitoring is carried out with the front UEGO sensors properly working. Because the SAIR diagnostic is run at idle conditions and cannot be executed at the same time as the front UEGO sensor Response Rate diagnostic

7 Automobili Lamborghini s.p.a. OBDII MY 07 Section 5 Page 7 Step 2: AS_DG_Status = 2 If the idle conditions are stable for a preset time, the SAIR strategy switches on the air pump and actives the electronic valve with a calibrated duty cycle. Step 3: AS_DG_Status = 3 If the idle conditions are stable for a preset time, the diagnostic checks the catalyst temperature (TCAT) for being below its threshold in order to prevent any damage to the catalyst. Step 4: AS_DG_Status = 4 The check of the front UEGO sensor output (Ip) is performed: t1 If Ip < Threshold the pending fault code is stored. t0 After a calibrated time the air pump and the electronic valve are switched off and the front UEGO sensor control is turned on in closed loop. The diagnostic is ended.

8 Automobili Lamborghini s.p.a. OBDII MY 07 Section 5 Page 8 PNEUMATIC VALVE DIAGNOSTIC. After every SAIR activation it is important to check that the two pneumatic valves close after the electro valve switching off. For this reason, the electrovalve is switched off before the SAIR pump. In this way, if one valve is stuck open and no fuel cut strategies activated, the rear oxygen sensor signal will remain stuck to lean until the SAIR pump is switched off. This strategy is performed every time the electrovalve is switched off.

9 Automobili Lamborghini s.p.a. OBDII MY 07 Section 5 Page 9 Mode/Service 6 communication

10 Automobili Lamborghini s.p.a. OBDII MY 07 Section 5 Page 10 In the following chart there are the data related to Secondary Air System monitoring strategy in accordance whit specification SAEJ1979 and allow access to the results for on-board diagnostic monitoring tests of specific components/systems that are not continuously monitored. J1979 SECONDARY AIR SYSTEM MONITOR SERVICE $06 DATA Test Comp Bit INIT Treshold ID ID TTL Description Value Error Conversion Secondary Air System circuit performance Right 0 V 0,25 V 4.88mV/lsb Secondary Air System circuit performance Left 0 V 0,25 V 4.88mV/lsb