The amount of intake air flow must be inputted to ECM in order to determine the fuel injection quantity. To measure the pressure inside of intake manifold, MAFS is used at idle and MAPS is required at accelerating. MAPS(Manifold Absolute Pressure) calculates the amount of air indirectly as measuring the pressure inside of intake manifold. This system is called a 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.
The 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 output by the transformation of diagphragm according to the change of pressure inside of intake manifold.
If the signal output of MAP sensor is stuck under enable conditions, ECM determines that a fault exists and a DTC is stored. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.
Item | Detecting Condition | Possible Cause |
DTC Strategy |
•
Monitor the MAP sensor's signal | 1. Faulty MAPS |
Enable Conditions |
•
No Disabling Fault Present
•
Shutdown time > 20 minutes
•
Engine running | |
Threshold value |
•
The difference between the signal at key-on and the signal at engine start < 0.5 kPa | |
Diagnosis Time |
•
For 3 seconds out of 5 seconds | |
MIL On Condition |
•
NO MIL ON(DTC only) |
Pressure(kPa) | Voltage(V) |
20 | 0.79 |
46.66 | 1.84 |
101.32 | 4.0 |
Fig.1) Normal graph of the MAP at the time when engine starts.
