Barometric Pressure Sensor: Testing and Inspection
System Schematic:
To test the Barometric Pressure Sensor, located on the air flow sensor, in the air cleaner housing. Remove the air flow sensor (AFS) connector and proceed as follows.
1. Connect a voltmeter between terminals 3 and 1 of the AFS Sensor connector.
Terminal 3: Barometric sensor output
Terminal 1: sensor 5V power supply
2. Warm the engine and bring it to a normal idle.
Barometric Pressure Sensor Test:
3. Slowly cover about half of the air cleaner air intake, observing the change in voltage. As pressure falls (vacuum increases), you should observe a drop in voltage. This should be sufficient to determine if the sensor is functional.
As a reference, at sea level conditions, with the use of a vacuum gauge, place the gauge hose inside the air filter intake and observe the vacuum as you increase the engine RPM.
Ambient pressure (engine off)...Approx. 4.00v
Vacuum 16in.Hg Approx. 1.75-1.90
Vacuum 24in.Hg Approx. 0.70-0.80v
Pressure 100 KPa (14.2 psi) Approx. 4.00v
Pressure 49 KPa (7.0 psi) Approx. 1.84v
Pressure 20 KPa (2.8 psi) Approx. 0.79v
4. Replace the air flow sensor if necessary.
HARNESS TEST:
1. Disconnect the air flow sensor connector and Turn on the ignition.
2. Using a voltmeter, measure the power supply voltage between the harness connector terminal 1 and ground.
Voltage: 4.8 - 5.2 Volts.
3. Check for continuity between the air flow sensor harness connector terminal 4 and ground and the engine control unit connector 4 and ground.
Continuity: Should Exist
4. Turn off the ignition and disconnect the engine control unit connector and check for continuity between the air flow sensor harness connector terminal 3 and the engine control unit harness connector terminal 16.
Continuity: Should Exist
5. Check for continuity (short) to ground between the air flow sensor harness connector terminal 3 and the engine control unit harness connector terminal 16.
Continuity : Should not Exist
6. Check for continuity between the air flow sensor harness connector terminal 3 and the engine control unit harness connector terminal 16.
Continuity : Should Exist
If any of the previous tests produce unsatisfactory results, the harness will need to be repaired or replaced. Once repairs have been completed, road test the vehicle to confirm that the repair has corrected the problem.
If the problem returns, it is possible that there is an intermittent failure of the component or the ECU. Check for looseness at all harness junctions and test for an intermittent failure.