'93 Mirage 1.5 motor, 148k. What would low output voltage of a MAP sensor cause?
Key on, engine off. . .3.87 at pin 2 (1050 feet above sea level. . .ok)
Key on, engine hot idle . . .1.38 at pin 2 . . .?
Poor start, very poor gas millage
OBD II Fault Code
Fault Code Definition
What does this mean?
The Mass Airflow Sensor (MAF) measures the amount of air entering the engine and the Engine Control Module (ECM) uses the information to determine the proper amount of fuel quantity and ignition timing.
Code P0102 sets when the ECM detects a low voltage output from the Mass Air flow Sensor.
Symptoms
Common Problems That Trigger the P0102 Code
Common Misdiagnosis
OPERATION
See Figures 1, 2 and 3
Fig. Fig. 1: MAP sensor location-2.4L engine
Fig. Fig. 2: MAP sensor location-3.0L engine
Fig. Fig. 3: MAP sensor location-3.3L and 3.8L engines
The PCM supplies 5 volts of direct current to the Manifold Absolute Pressure (MAP) sensor. The MAP sensor then converts the intake manifold pressure into voltage. The PCM monitors the MAP sensor output voltage. As vacuum increases, the MAP sensor voltage decreases proportionately. Also, as vacuum decreases, the MAP sensor voltage increases proportionally.
With the ignition key ON , before the engine is started, the PCM determines atmospheric air pressure from the MAP sensor voltage. While the engine operates, the PCM figures out intake manifold pressure from the MAP sensor voltage. Based on the MAP sensor voltage and inputs from other sensors, the PCM adjusts spark advance and the air/fuel ratio. The MAP sensor is mounted to the intake manifold, near the throttle body inlet to the manifold. The sensor connects electrically to the PCM.
TESTING
See Figures 4, 5, 6 and 7
Fig. Fig. 4: Disengage the MAP sensor connector-3.0L engine shown
WARNING
When testing the MAP sensor, make sure the harness wires do not become damaged by the test meter probes.
Fig. Fig. 5: MAP sensor connector terminal identifications: (A) 5-volt supply, (B) sensor signal, (C) ground-3.0L engine shown
Fig. Fig. 6: MAP sensor connector terminal identifications-2.4L, 3.3L and 3.8L engines
Fig. Fig. 7: Using a digital volt-ohmmeter, test the MAP sensor voltage-3.0L engine shown
REMOVAL & INSTALLATION
See Figures 1, 2, 3 and 4
The MAP sensor is mounted on the intake manifold near the throttle body inlet to the manifold.
OPERATION
The Manifold Absolute Pressure (MAP) sensor, used on 1996-99 vehicles, measures the changes in intake manifold pressure which result from engine load/speed changes, and converts this information to a voltage output. The MAP sensor reading is the opposite of a vacuum gauge reading: when manifold pressure is high, MAP sensor value is high and vacuum is low. A MAP sensor will produce a low output on engine coast-down with a closed throttle while a wide open throttle will produce a high output. The high output is produced because the pressure inside the manifold is the same as outside the manifold, so 100 percent of the outside air pressure is measured.
The MAP sensor is also used to measure barometric pressure under certain conditions, which allows the PCM to automatically adjust for different altitudes.
The MAP sensor changes the 5 volt signal supplied by the PCM, which reads the change and uses the information to control fuel delivery and ignition timing.
TESTING
See Figures 1 and 2
Fig. Fig. 1: Manifold Absolute Pressure (MAP) sensor circuit
When pumping up and releasing the vacuum, check to make sure the voltage readings are smooth. When applying vacuum to the sensor, the change in voltage should happen instantly. A slow change in voltage could point to a faulty sensor.
Fig. Fig. 2: MAP sensor voltage specifications
REMOVAL & INSTALLATION
3.8L (VIN K) Engine
See Figure 4
On these engines, the MAP sensor is mounted to the PCV valve cover.
Fig. Fig. 4: On the 3.8L (VIN K) engine, the MAP sensor (1) is mounted in the PCV valve cover (2)
To install:
Manifold Absolute Pressure (MAP) sensor measures the changes in the intake manifold pressure which result from engine load and speed changes, and converts this measurement into a voltage output.
A closed throttle on when the engine is decelerating would produce a relatively low MAP output, while a wide open throttle would produce a high output. Manifold absolute pressure is the opposite of what you would measure on a vacuum gage. When manifold pressure is high, vacuum is low. The MAP sensor is also used to measure barometric pressure under certain conditions, which allows the PCM to automatically adjust for different altitudes.
The PCM sends a 5 volt reference signal to the MAP sensor. As the manifold pressure changes, the electrical resistance of the sensor also changes. By monitoring the sensor output voltage, the PCM can determine the manifold pressure. A higher pressure, low vacuum (high voltage) requires more fuel, while a lower pressure, higher vacuum (low voltage) requires less fuel.
A high or low voltage fault in the MAP sensor circuit should set a DTC P0107 or DTC P0108. If the MAP sensor sends an intermittent zero voltage signal to the PCM, a DTC P0106 will set.
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