See Figure 1
On 1996-99 vehicles, the IAT and Manifold Absolute Pressure (MAP) sensors are combined into a single sensor which is attached to the intake manifold. Refer to the IAT sensor information, located earlier in this section for operation, testing and removal and installation.
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.
See Figures 2 and 3
- Visually check the connector, making sure it is attached properly and all of the terminals are straight, tight and free of corrosion.
- Test the MAP sensor output voltage at the sensor connector between terminals 1 and 3, as shown in the accompanying figure.
- With the ignition switch ON and the engine not running, then output voltage should be 4-5 volts. If OK, go to next step. If not OK, go to step 4.
- Test the PCM terminal 29 for the same voltage described in the previous step to make sure the wire harness is OK. Repair as necessary.
- Test the MAP sensor ground circuit at the sensor connector terminal 1 and PCM terminal 51. If OK, go to the next step. If not OK, repair as necessary.
- Test the MAP sensor supply voltage between the sensor connector terminals 2 and 1 with the ignition key in the ON position. The voltage should be about 3.5-5.5 volts. There should also be 3.5-5.5 volts at terminal 43 of the PCM. If OK, replace the MAP sensor. If not, repair or replace the wire harness as required.
REMOVAL & INSTALLATION
See Figures 1, 4 and 5
- Disconnect the negative battery cable.
- Detach the electrical connector from the MAP sensor.
- Unfasten the mounting screws, then remove the MAP sensor from the vehicle.
- Insert the sensor into the intake manifold, but be careful not to damage the sensor O-ring seal.
- Tighten the sensor mounting screws to 20 inch lbs. (2 Nm).
- Attach the sensor electrical connector.
- Connect the negative battery cable.