Manifold Pressure/Vacuum Sensor: Testing and Inspection

INSPECTION

There are two tests of the Manifold Absolute Pressure (MAP) Sensor; Electrical test and Mechanical test.

Electrical Test
1. Turn ignition switch off. Disconnect the three pin connector from the MAP sensor. Turn ignition on.

MAP Sensor Connector Terminal Identification:

2. Measure voltage between RED/WHITE (+) terminal and chassis ground. Voltage should read 5.0 volts.
3. Measure voltage between RED/WHITE (+) terminal and BLUE/WHITE (-) terminal. Voltage should read 5.0 volts.
4. Measure voltage between WHITE/BLUE (+) terminal and BLUE/WHITE (-) terminal. voltage should read 5.0 volts.
5. Turn ignition switch off. Reconnect the three pin connector at the Map sensor. Connect the test harness between the Programmed Fuel Injection Electronic Control Module (PGM-FI ECM) and the harness. Turn ignition switch on.

PGM-FI ECM Connector Description And Wire Location:

6. Measure voltage between terminals D17 (+) and D21 (-). Voltage should read 3.0 volts. If not, replace MAP sensor. If voltage OK, substitute known good PGM-FI ECM and retest.

NOTE: If voltage readings at steps 2,3 and 4 do not test ok, inspect RED/WHITE (+), BLUE/WHITE (-) and WHITE/BLUE (+) wires between the three pin connector and the PGM-FI ECM harness connector for shorts and opens.

Mechanical Test
1. Turn ignition switch off.

MAP Sensor Testing:

2. Disconnect #21 vacuum hose from the throttle body and apply vacuum. It should hold vacuum (if it does not hold vacuum, test MAP sensor separately from hose. If MAP sensor still does not hold vacuum, replace MAP sensor).

MAP Sensor Testing:

3. Install a tee fitting in line with hose #21 from the throttle body to the MAP sensor. Start engine and run at idle, measure vacuum. Vacuum should read manifold vacuum.
4. Turn ignition switch off. Install test harness between PGM-FI ECM and harness connector. Turn ignition switch on.

PGM-FI ECM Connector Description And Wire Location:

5. Measure voltage between terminal D17 (+) and terminal D21 (-). Voltage should read 3.0 volts (if not, replace MAP sensor).
6. Start engine and run at idle. Voltage should now read 1.0 volt (if not, replace MAP sensor). If voltage tests OK but DTC indication/symptom still exist, substitute known good PGM-FI ECM and retest.