Manifold Absolute Pressure (MAP) Sensor (C-1)

A malfunction in the MAP sensor circuit should set a related trouble code in ECM memory. If a code is present, see appropriate G - TBI TESTS W/ CODES (for Throttle Body Injected models) and G - PFI TESTS W/ CODES (for Port Fuel Injected models) article in this section. An out-of-calibration sensor may not set a trouble code. Use following procedure to test sensor calibration. If driveability problems exist, MAP sensor failure is suspected and no MAP code is present, disconnect MAP sensor connector. See Fig 1 . If driveability condition improves, replace MAP sensor.
With ignition on and engine off, check MAP sensor parameter using a "Scan" tester connected to the ALDL connector. Voltage should be as specified in MAP SENSOR VOLTAGE RANGE table. If MAP sensor voltage is as specified, go to step 3). If voltage is not as specified, check for 5-volt reference supplied to sensor. Check harness integrity. If no problems are evident, replace MAP sensor.
Using a hand-held vacuum pump, apply 10 in. Hg to MAP sensor, and note voltage change. Voltage should drop about 1.2-2.3 volts less than as specified in table. If voltage is not as specified or voltage reading does not immediately follow vacuum change, MAP sensor is faulty.

Fig 1: Typical MAP Sensor Circuit

Courtesy of GENERAL MOTORS CORP.

MAP SENSOR VOLTAGE RANGE