1996 PCED OBDI
SECTION 18: Diesel Diagnosis — 7.3L DI Engine
AC: Barometric Pressure (BARO) Sensor
Introduction
  AC: Pinpoint Tests  
Signal Functions

The barometric pressure (BARO) sensor is a variable capacitance sensor that when supplied with a 5 volt reference signal from the powertrain control module (PCM) produces a linear analog voltage signal that indicates pressure.

Timing Control — The BARO signal is used to determine altitude to adjust timing and fuel quantity to optimize engine operation and control smoke throughout all altitude conditions.

Glow Plug Control — The BARO signal is one of the variables used to calculate glow plug on time. At higher altitudes glow plug on time is increased to insure faster clean up of start-up smoke.





Detection/Management

A BARO signal that is detected out of range high or low by the PCM will cause the PCM to ignore the BARO signal and use the manifold absolute pressure (MAP) signal generated at low idle as an indication of barometric pressure.





Note

After removing connectors, always check for damaged pins, corrosion, loose terminals etc.



CONNECTOR CHECKS TO GROUND (B-)
(CHECK WITH SENSOR CONNECTOR DISCONNECTED AND IGNITION KEY OFF, ALL ACCESSORIES OFF)
Test PointsSpec.Comments
1 to Grd<5 ohmsResistance to chassis ground check with key off. If greater than 5 ohms, the harness is open.
2 to Grd>5 ohmsResistance less than 5 ohms indicates a short to ground.
3 to Grd>5 ohmsResistance less than 5 ohms indicates a short to ground.



CONNECTOR VOLTAGE CHECKS
(CHECK WITH SENSOR CONNECTOR DISCONNECTED AND IGNITION KEY ON)
Test PointsSpec.Comments
1 to Grd0-.25 voltIf greater than .25 volts, signal wire is shorted to VREF or battery.
2 to Grd5 voltsVREF signal should be 5 volts ± 0.5 volt.
3 to Grd0-.25 voltSignal voltage. If greater than .25 volts, shorted to VREF or battery.



HARNESS RESISTANCE CHECKS
(CHECK WITH BREAKOUT BOX INSTALLED ON ENGINE HARNESS ONLY)
Test PointsSpec.Comments
No. 91 to 1<5 ohmsResistance from sensor connector to 104-pin connector.
No. 90 to 2<5 ohmsResistance from sensor connector to 104-pin connector.
No. 84 to 3<5 ohmsResistance from sensor connector to 104-pin connector.

DTC Descriptions

Circuit Faults:

0107 = BARO sensor circuit low input.

0108 = BARO sensor circuit high input.

 

 

  AC: Pinpoint Tests