EGR CONTROL OPERATION [WL-C, WE-C]

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EGR Valve Operation

•  To improve emission performance, target EGR valve position is decided based on intake air flow, engine speed, engine coolant temperature and fuel injection amount.
•  The flow amount of the EGR is calculated from the difference between the following amounts.
―  Target intake air amount that is mainly calculated from engine speed and fuel injection amount
―  Actual intake air amount that is mainly detected by MAF sensor/IAT sensor No.2
•  The PCM controls the vacuum applied to the EGR valve by opening and closing a two-duty solenoid valve.

Intake Shutter Valve Operation


Close condition

•  The PCM turns on the intake shutter solenoid valve (half) and the intake shutter solenoid valve (full) in order to close the intake shutter valve when the engine switch is at OFF.


Halfway open condition (WE‐C)

•  The PCM turns the intake shutter solenoid valve (half) on when all of the following conditions are met.
―  Engine coolant temperature is above threshold level.
―  Intake air temperature is threshold level.
―  Barometric pressure is above threshold level.
―  Engine speed is below threshold level.
―  Vehicle speed is below threshold level.
―  Fuel injection amount is below threshold level.


Full open condition

•  For conditions other than closed and halfway open, the PCM turns off the intake shutter solenoid valve (half) and the intake shutter solenoid valve (full) in order to open the intake shutter valve.


MAF Learning

•  After learning is initiated, the PCM calculates the actual intake air amount for the complete learning period.
•  The PCM calculates the deviation between the target and actual intake air amount, then, based on the deviation, derives the learning factor. The PCM stores the learning factor and uses it to correct the intake air amount. Due to this, the error margin of the MAF sensor is resolved. If the deviation factor is less than the specified amount, the PCM does not calculate nor update the learning factor.
•  The PCM stores the learning factor until the next time the factor is updated. The factor is erased using the Mazda Modular Diagnostic System (M-MDS).

Using the Mazda Modular Diagnostic System (M-MDS) for learning

•  By using the Mazda Modular Diagnostic System (M-MDS), the learning function can be freely controlled. Due to this, even if the PCM or MAF sensor/IAT sensor No.2 is replaced, the learning factor can be stored again.
•  When using the Mazda Modular Diagnostic System (M-MDS) to control the MAF learning function, learning is performed at the following three engine speed levels.
―  720 rpm
―  1,850 rpm
―  2,500 rpm


Without using the Mazda Modular Diagnostic System (M-MDS) for learning

•  By shorting circuit the DLC terminal TEN five times within 5 s, the learning function can be freely controlled. Due to this, even if the PCM or MAF sensor/IAT sensor No.2 is replaced, the learning factor can be stored again.
•  The glow indicator light illuminates while MAF learning is performed, and flashes five times after it is completed.