Circuit Description
The manifold absolute pressure (MAP) sensor measures the changes in the intake manifold pressure which result from engine load, intake manifold vacuum, and RPM changes. The MAP sensor converts these changes into a voltage output. The engine control module (ECM) sends a 5-volt reference voltage to the MAP sensor. As the intake manifold pressure changes, the output voltage of the MAP sensor also changes. A low voltage, high vacuum, output of 1-2 volts is present at idle. A high voltage, low vacuum, output of 4-4.8 volts is present at wide open throttle. The MAP sensor is also used under certain conditions to measure barometric pressure. This allows the ECM to make adjustments for altitude changes. The ECM uses the MAP sensor for fuel delivery and ignition timing changes.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Applying 34 kPa (4.9 psi) of vacuum to the MAP sensor should cause the voltage to change. Subtract the second voltage reading from the first. That voltage value should be more than 1.5 volts. When applying vacuum to the MAP sensor, the change in the voltage should happen instantly. A slow voltage change indicates a faulty MAP sensor.
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Disconnect the MAP sensor from the bracket and twist the MAP sensor. Output changes more than 0.1 volt indicate a faulty connector or connection.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 |
Is the difference in the 2 voltage readings less than the specified value? | 0.4 V | Go to Step 2 | Go to Step 5 |
Is the difference in voltage readings greater than the value specified? | 1.5 V | System OK | Go to Step 3 | |
Inspect the MAP sensor connector terminals. Is a repair necessary? | -- | Go to Step 4 | Go to Step 5 | |
4 | Repair the MAP sensor connector terminals as needed. Did you complete the repair? | -- | System OK | -- |
5 | Replace the MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Did you complete the replacement? | -- | System OK | -- |
