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 MAFS 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
As often as possible, the MAPS signal should be compared with the TPS signal. Check whether the MAPS and TPS signals increase at the same time when accelerating. During acceleration, the MAPS output voltage increases; during deceleration, the MAPS output voltage decreases.