Code 34 - Differential Pressure (Vac) Sensor
Code 34 indicates that ECM has seen the following:
- Pressure outside a specified voltage range (seen by ECM as voltage at terminal No. 20).
- Engine RPM less than a given value.
- Engine at operating temperature.
- All the above conditions exist for a time greater than specified.NOTE: Test numbers refer to test numbers on diagnostic chart.
- 1) This tests output of sensor at idle to determine if sensor is within specification. Normal sensor will read .50-.64 volt with ignition switch in the "ON" position and engine not running.
- 2) Signal voltage should read greater than 2 volts with engine idling and a minimum of 15 in. Hg vacuum.
- 3) If voltage reads less than 2 volts and adequate vacuum was available at sensor, VAC sensor is faulty.
- 4) If voltage remains greater than .5 volt with sensor harness disconnected, fault is in harness or ECM. Low voltage indicates a faulty vacuum sensor.
- 5) If voltage remains low when harness terminals "B" and "C" are jumped together, fault is in harness or ECM. High voltage indicates a faulty vacuum sensor.