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 the step numbers on the Diagnostic Table.
Important: Be sure to use the same diagnostic test equipment for all measurements.
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Applying 34 kPa (10 in of Hg) vacuum to the MAP sensor should cause the voltage to be 1.5 to 2.1 volts less than the voltage at Step 3. Upon applying vacuum to the sensor, the change in voltage should be instantaneous. A slow voltage change indicates a malfunctioning sensor.
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Check vacuum hose to sensor for leaking or restriction. Be sure that no other vacuum devices are connected to the MAP hose.
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Important: Make sure electrical connector remains securely fastened.
Move sensor electrical connector by hand only while watching scan tool to check for intermittent connection. Output changes more than 0.10 volt indicate a bad connection. If OK, replace sensor.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
2 |
Were any MAP DTCs set? | -- | Go to the applicable DTC table | |
3 |
Are the voltage readings between the 2 vehicles within the specified value? | ± 0.4V | ||
Is the difference more than the specified value? | 34 kPa (10 in of Hg) 1.5V | |||
5 | Replace MAP sensor. Refer to Manifold Absolute Pressure Sensor Replacement . Is the action complete? | -- | -- | |
Check MAP sensor vacuum source for leakage or for a restriction and be sure that the vacuum source supplies the MAP sensor only. Was a problem found? | -- | |||
Check MAP sensor harness connector terminals and repair as necessary. Was a repair necessary? | -- | |||
8 | Repair leakage or restriction in MAP sensor vacuum source. Is the action complete? | -- |
| |
9 | Operate the vehicle within the conditions under which the original symptom was noted. Does the system now operate properly? | -- | System OK |
