P1123
OVERVIEWAir/Fuel Mixture Ratio Control Feature of the Multiport Fuel Injection (MFI) System
The MFI system is a system which employs the signals from the heated oxygen sensor to activate and control the injector installed in the manifold for each cylinder, thus precisely regulating the air / fuel mixture ratio and reducing emissions.
This in turn allows the engine to produce exhaust gases of the proper composition to permit the use of a three way catalyst. The three way catalyst is designed to convert the three pollutants (1) hydrocarbons (HC), (2) carbon monoxide (CO), and (3) oxides of nitrogen (NOx) into harmless substances. There are two operating modes in the MFI system.
1. Open loop air/fuel ratio is controlled by information programmed into the ECM.
2. Closed loop air/fuel ratio is varied by the ECM based on information supplied by the oxygen sensor.
TROUBLESHOOTING HINTS
Air/Fuel ratio stays rich or lean longer than specified period because of system malfunction.
This diagnostic trouble code (DTC) can not be assigned to any single component because the trouble code represents an overall failure within the Air/Fuel Mixture Ratio Control feature of the MFI System. Since the failure of many interelated components could cause this type of malfunction, it is important that the entire MFI system is evaluated.
NOTE: It is highly possible that this DTC will be accompanied by additional DTCs that could prove helpful in narrowing the scope of potential MFI components to investigate.
AIR-FUEL CONTROL TROUBLESHOOTING PROCEDURE