MAP Sensor Output Diagnosis

MAP Sensor Output Check (1 Of 2):

MAP Sensor Output Check (2 Of 2):

MAP Sensor:

Circuit Description
The Manifold Absolute Pressure (MAP) sensor measures the changes in the intake manifold pressure which result from the engine load (intake manifold vacuum) and the RPM changes then converts these into a voltage output. The Powertrain Control Module (PCM) supplies a 5 volt reference voltage to the MAP sensor. As the manifold pressure changes, the output voltage of the sensor also changes. By monitoring the sensor output voltage, the PCM knows the manifold pressure. A lower pressure (low voltage) output voltage will be about 1.0 to 1.5 volts at idle. While high pressure (high voltage) output voltage will be about 4.5 to 4.8 volts at Wide Open Throttle (WOT). The MAP sensor is also used, under certain conditions, to measure barometric pressure, allowing the PCM to make adjustment for different altitudes. The PCM uses the MAP sensor in order to control the fuel delivery and the ignition timing.

Test Description
The numbers below refer to step numbers in the diagnostic table.

1. The OBD System Check prompts the technician to store the Freeze Frame Data in the scan tool. This creates an electronic copy of the freeze frame data taken when the fault occurred that can be referred to later.
4. Applying 34 kPa (10" Hg) vacuum to the MAP sensor should cause the voltage to be 1.5 to 2.1 volts less than the voltage at Step 1. Upon applying the vacuum to the sensor, the change in the voltage should be instantaneous. A slow voltage change indicates a faulty sensor.
5. Check the vacuum hose to the sensor for leakage or restrictions. Do not connect other vacuum devices to the MAP sensor hose.
7. Move the MAP sensor electrical connector by hand (only) while watching the scan tool in order to check for an intermittent connection. The output changes greater than 0.10 volt indicate a bad connection.