Slow Change In Idle MAP Sensor Signal

WHEN MONITORED
With engine speed between 600 and 1500 RPM, and TPS voltage less than 1.0 volt.

SET CONDITION
The variation in MAP signal is less than 0.157 volt between firing pulses of the engine.

THEORY OF OPERATION
This sensor provides a 0 to 5 volt signal to PCM cavity 1, which represents Manifold Absolute Pressure (MAP), (while the engine is running), and ambient barometric pressure (when the engine is OFF).

- Low voltage output signal (0.5 to 1.8 volts) at idle, (when manifold vacuum is high).

- High voltage output signal (3.9 to 4.8 volts), at deep throttle (when manifold vacuum is low).

The MAP sensor receives a 4.8 to 5.1 volt supply from PCM cavity 6, and a sensor ground from PCM cavity 4.

PROBABLE CAUSES
- Restricted or leaking vacuum/pressure to MAP sensor
- Ice in sensor or passage).
- Failed sensor
- Failed PCM