Manifold Pressure/Vacuum Sensor: Testing and Inspection

MAP Sensor Description:

NOTE: Before starting the test, check the condition of the electrical and vacuum hose connections. Repair if needed.

1. Turn the ignition switch ON (the engine should remain off), and test the voltage from connector terminal B to ground with a voltmeter. Voltage should be between 4 to 5 volts. With the engine started, warmed to normal operating temperature, and idling, the voltage output should drop to 1.5 to 2.1 volts.
2. Check for voltage at the engine controller electrical terminal 5 under the same conditions as in step 1. The voltage readings should be the same as in step 1. If the voltages are different, then the wiring harness should be suspected as the problem area.
3. Check the supply voltage to the sensor by connecting a voltmeter to connector terminal C and a ground. Voltage reading should be 5 +/- 0.5 volts with the ignition switch ON. There should also be 5 +/- 0.5 volts at the engine controller electrical terminal 6. Repair wiring harness if necessary.
4. Check the sensor ground circuit between electrical terminal A on the sensor and engine controller connector terminal 4. Connect one lead of an ohmmeter to electrical terminal A of the sensor and the other to SBEC II connector terminal 4. The ohmmeter should indicate continuity. Repair wiring harness if necessary.
5. Check the sensor ground circuit at the engine controller electrical connector. Connect an ohmmeter between terminals 4 and 11 of the engine controller electrical connector. If the ohmmeter does not indicate continuity, check the sensor ground connection at the right side of the engine block behind the oil dipstick. If the ground connection is good, replace the engine controller.

WARNING: If the engine controller connector terminal 4 has a short to 12 volts (battery voltage), this is most likely the reason the first engine controller failed; consequently, it is imperative that this circuit be repaired before installing a new engine controller.