Barometric Pressure Sensor: Testing and Inspection

Fig. 4 Three Terminal Plug Pin Designations:

The altitude sensor contains a barometric element which reacts to changes in air pressure, and in turn moves an electrical contact across a resistance track.
The signal generated by the altitude sensor is used by the injection control unit to correct the fuel mixture relative to the altitude or air pressure. The ignition control unit also uses this signal to modify the ignition timing curve for certain engine loads at higher altitudes.
The altitude sensor is mounted on the ignition control unit mounting bracket behind the left kick panel.
1. Disconnect the harness plug from the altitude sensor.
2. Connect a voltmeter between terminal 2,Fig. 4, of the harness plug and ground. With the ignition ON, approx. 5vdc should be available.
3. Connect voltmeter between terminals 2 and 3 of the harness plug. With the ignition ON, 5vdc should be available.
4. If no voltage is available, check wiring between the altitude sensor harness plug and both control unit plugs. Pin designations are:
1 -- 25 (injection control unit)
1 -- 2 (ignition control unit)
2 -- 21 (ignition control unit)
3 -- ground
5. If wiring and voltage are correct, replace the altitude sensor.