General Information

Engine Control
P0108 Manifold Absolute Pressure/Barometric Pressure Circuit High Input - General Information

Component Location





General Description

In order to determine the correct amount of fuel, the PCM uses the MAP to help determing the amount of intake air flow. To measure the air flow in the intake manifold, the MAFS is used at idle and MAPS is required during accelerating. The 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, PCM calculates the amount of intake air flow. The MAPS is mounted on the surge tank to measure the pressure inside of intake manifold, and it consists of a piezo electric element and a hybrid IC which amplifies the output signal from the element. A diaphragm with a piezo electric element is use to convert pressure into voltage. One side of the diaphragm has a chamber with a fixed (absolute) pressure while intake pressure is applied to the other side. As the intake manifold pressure changes, the diaphram moves which changes a voltage output.

DTC Description

Checking output signals of MAPS every 5 sec. under detecting condition, if an output signal is above 4.5V for more than 2.5 sec., PCM sets P0108.

DTC Detecting Condition





Specification





Diagnostic Circuit Diagram





Signal Waveform & Data








Fig.1) Normal waveform of MAPS & TPS with acceleration.
Fig.2) Normal data of MAPS at idle.

It is necessary that MAPS should be checked along with TPS. Because the MAP/TPS rationality diagnostic is comprised of two tests. A deceleration test is performed to provide a robust method for detection of an altitude compensated MAP value that is too high for the deceleration condition. The second test compares the altitude compensated MAP value to both high and low limits, dependent upon throttle position and engine speed. When the MAP value is out of the threshold range, the MAP/TPS system is determined to be failed.