The most important information for measuring engine fuel requirements comes from the pressure sensor. Using the pressure and temperature data, the PCM calculates the intake air mass. It is connected to the engine intake manifold through a hose and takes readings of the absolute pressure. A piezoelectric crystal changes a voltage input to a frequency output which reflects the pressure in the intake manifold.
Atmospheric pressure is measured both when the engine is started and when driving fully loaded, then the pressure sensor information is adjusted accordingly.
The MAP sensor is a variable capacitor sensor that is supplied a 5-volt reference signal by the PCM and returns a voltage signal to the PCM relative to the intake manifold pressure. The sensor voltage increases as the pressure increases. The MAP sensor allows the PCM to determine the engine boost to calculate fuel quantity. In addition, the MAP signal is used to control smoke by limiting fuel quantity during acceleration until a specified boost pressure is obtained, and is used by the PCM for EGR system calculations and control.
A MAP signal concern detected by the PCM causes the PCM to calculate an estimated manifold pressure based on known engine conditions.
Removal & Installation
6.0L Diesel Engine
- Before servicing the vehicle, refer to the Precautions section.
- Turn the ignition switch to the OFF position.
- Disconnect the manifold absolute pressure (MAP) sensor.
- Disconnect the pressure hose.
- Disconnect the electrical connector.
- Remove the mounting screws and the MAP sensor.
- To install, reverse the removal procedure.
- Connect MAP/BARO tester to the sensor connector and sensor harness connector. With ignition ON and engine OFF, use DVOM to measure voltage across tester terminals. If the tester's 4-6V indicator is ON, the reference voltage input to the sensor is okay.
- Measure the reference signal of the MAP sensor. If the DVOM voltage reading is as indicated in the table, the sensor is okay.
Before servicing the vehicle, refer to the Precautions section.
WARNINGUse only a high-impedance multimeter, otherwise damage to the PCM and/or sensors can result.
- Disconnect the pressure hose from the MAP sensor.
- With the key ON, engine OFF, connect the Pressure Adapter Kit 014-00761, or equivalent (gauge bar), and apply pressure to the MAP sensor.
- Backprobe MAP sensor connector pin 2 and measure the voltage between pin 2 and ground.
Compare the values with the pressure/voltage table.