Honda Pilot: PGM-FI System Description - A/F Sensor/HO2S Feedback Air/Fuel Ratio Control

Air fuel ratio control is part of fuel injection control and comprises the steps of:

• Calculating basic injection amount from intake air flow amount and engine speed
• Calculating air fuel ratio correction value from the oxygen density in the exhaust gas and reflecting the calculated values to the injection amount

Air fuel ratio control stops feedback under the following conditions in order to maintain operational performance and catalytic protection.

• When starting the engine or during fuel increase after the engine is started
• While the engine coolant is cold
• During fuel increase under high load
• During fuel increase at high engine speed
• During fuel cut-off at deceleration

Air Fuel Ratio (A/F) Sensor (Sensor 1)

The air fuel ratio (A/F) sensor (Sensor 1) is installed on the warm up three way catalytic converter (WU-TWC). Air fuel ratio control performs fuel injection control based on the oxygen density detected in exhaust gas in order to bring the intake mixture in the vicinity of a target air fuel ratio.

This high-precision air fuel ratio control is achieved by detecting a correction value with an A/F sensor (Sensor 1) and then applying further correction with a secondary heated oxygen sensor (secondary HO2S) (Sensor 2).

The sensor element and the heater inside the A/F sensor (Sensor 1) have a layered construction of a plate-shaped zirconia element whose inside and outside are coated with platinum and a built-in platinum heater. A ceramic coating diffusion layer on the platinum electrode on the outside of the element creates an atmospheric chamber between the platinum electrode inside the element and the heater.

Secondary HO2S (Sensor 2)

The secondary heated oxygen sensor (secondary HO2S) (Sensor 2) is installed downstream of the warm up three way catalytic converter (WU-TWC), and it detects the oxygen density in the exhaust gas passing through the catalyst and outputs it to the powertrain control module (PCM) to enable the high-precision air fuel ratio control, which cannot be achieved only with an A/F sensor (Sensor 1).

Inside secondary HO2S (Sensor 2) is a test tube shaped zirconia element whose inside and outside surfaces are coated with platinum. The inside surface is exposed to the atmosphere, while the outside surface is within the exhaust gas.

A ceramic heater is equipped inside the element in order to shorten sensor reaction time and to enable output that is constantly stable.

PGM-FI System Description - Components

1. FRONT A/F SENSOR (BANK 2, SENSOR1)
2. REAR A/F SENSOR (BANK 1, SENSOR 1)
3. FRONT SECONDARY HO2S (BANK 2, SENSOR 2)
4. REAR SECONDARY HO2S (BANK 1, SENSOR 2)
5. MAP SENSOR
6. ECT SENSOR 1
7. MAF SENSOR/IAT SENSOR
8. KNOCK SENSOR 2 (BANK 2)
9. KNOCK SENSOR 1 (BANK 1)
10. THROTTLE BODY
11. FUEL INJECTOR
12. FUEL RAIL PRESSURE SENSOR
13. FUEL PRESSURE REGULATOR
14. FUEL FILTER
15. FUEL PUMP
16. FUEL TANK
17. AIR CLEANER
18. INTAKE AIR RESONATOR
19. EGR VALVE AND EGR VALVE POSITION SENSOR
20. PCV VALVE
21. FRONT WU-TWC (BANK 2)
22. REAR WU-TWC (BANK 1)
23. UNDER-FLOOR TWC
24. EVAP CANISTER PURGE VALVE
25. FTP SENSOR
26. EVAP CANISTER
27. EVAP CANISTER VENT SHUT VALVE
28. FUEL TANK VAPOR CONTROL VALVE
29. HIGH PRESSURE FUEL PUMP
30. MIS-FUEL INHIBIT DEVICE

Parking and Back-Up Sensor System Description - ComponentsPGM-FI System Description - Electronic Control