Manifold Absolute Pressure (MAP) Sensor
- MAP sensor is mounted on engine cowl, above TBI unit. See Figure
. Map sensor is connected to intake manifold vacuum. When engine is off, MAP sensor functions as a barometric (BARO) sensor.
- To check sensor, turn ignition to ON position with engine off. Backprobe MAP sensor connector and measure voltage between terminals "A" (5-volt reference) and "C" (sensor ground). See Fig 1
.
- If voltage is not 5 volts, check continuity of 5-volt reference and ground circuits between ECM and sensor. Measure voltage at sensor connector terminal "B" (MAP signal).
- Voltage should be as specified in the MAP SENSOR VOLTAGE SPECIFICATIONS
table. If voltage is not within specification, replace MAP sensor. If voltage is within specification, connect a hand-held vacuum pump to sensor, and apply 10 in. Hg. Voltage should change immediately and be 1.2 volts less than previous reading.
- If voltage is not within specification or changes slowly, replace sensor. If a Scan tester is used, either voltage or kPa (kilopascals) pressure will be displayed.
MAP SENSOR VOLTAGE SPECIFICATIONS
| Altitude (Feet) |
Signal Voltage (Volts) |
| 1000 or less |
3.8-5.5 |
| 1000-2000 |
3.6-5.3 |
| 2000-3000 |
3.5-5.1 |
| 3000-4000 |
3.3-5.0 |
| 4000-5000 |
3.2-4.8 |
| 5000-6000 |
3.0-4.6 |
| 6000-7000 |
2.9-4.5 |
| 7000-8000 |
2.8-4.3 |
| 8000-9000 |
2.6-4.2 |
| 9000-10,000 |
2.5-4.0 |
Courtesy of GENERAL MOTORS CORP.