The amount of intake air flow must be inputted to ECM in order to determine the fuel injection quantity. MAPS(Manifold Absolute Pressure) calculates the amount of air indirectly as measuring the pressure inside of intake manifold. This mechanism is also called Speed-Density Type. MAPS transfers analog output signal which is proportional to the change of intake manifold pressure, then, with this signal and RPM, ECM calculates the amount of intake air flow. MAPS is mounted on surge tank to measure the pressure inside of intake manifold, and it consists of a piezo electric element and hybrid IC which amplifies output signal from the element. A piezo electric element is a sort of a diaphragm using piezo electric effect. One side of the diaphragm is surrounded with vacuum chamber while intake pressure is applied to the other side. Thus, signals are outputted by the transformation of diagphragm according to the change of pressure inside of intake manifold
ECM compares the MAPS output and calculated MAPS value while enable condition is met. If the acutal MAP value is higher than Maximum threshold or lower than Minimum threshold for a pre-determined time, ECM determines that a fault exists and a DTC is stored.
Item
Detecting Condition
Possible Cause
DTC Strategy
? Plausability check
? Dirty air cleaner.
? Oil Cap or Dipstick missing or not installed correctly.
? Air leak in intake system
? Contact resistance in connectors.
? Faulty MAPS or TPS
Enable Conditions
? No relevant failure
? 10 V= Battery voltage = 16V
? Lambda close loop control activated
Threshold Value
? Difference between model pressure and measured pressure > 280hpa
? Deviation value of fuel trim control > 20% or < -20%
Diagnostic Time
? 200 revolutions
MIL On Condition
? 2 Driving Cycles