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Home >> Jeep >> 2005 >> Wrangler Rubicon, Standard >> Repair and Diagnosis >> External Pages >> Different car >> Section 490 (Powertrain Diagnostic Procedures - Diesel) >> Diagnostic Information And Procedures >> DRIVEABILITY - Diesel - Symptoms >> Symptom: *CHECKING THE BOOST PRESSURE VACUUM SUPPLY >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2005 Jeep Liberty. However, it is still accessible from the selected car via links, so may be relevant.
DIAGNOSTIC PROCEDURES - CHECKING THE BOOST PRESSURE VACUUM SUPPLY

TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRBIII® display the ECM DTC's.
NOTE: Circuit related DTC's refers to DTC's containing Shorts to Ground, Shorts to Voltage Open Circuits, Signal High and Signal Low DTC's.

Does the DRBIII® display any ECM circuit related DTC's?
Yes --> Refer to the appropriate DTC information and repair the circuit DTC before continuing.
Perform ROAD TEST VERIFICATION - VER-2 .
No --> Go To 2		 All
2 Turn the ignition off.
Disconnect the vacuum hose at the Vacuum Reservoir Solenoid port A connector.
Connect a vacuum gauge to the disconnected hose.
Start the engine.
Observe the vacuum gauge reading.
Does the vacuum gauge indicate steady vacuum above 25 inches?
Yes --> Go To 3
No --> Go To 5		 All
3 Turn the ignition off.
Disconnect the vacuum hose at the Boost Pressure Solenoid port A connector.
Connect a vacuum gauge to the disconnected hose.
Start the engine.
Observe and note the vacuum gauge reading.
Observe and note the vacuum reading while turning the engine off.
NOTE: The vacuum reading should be above 25 inches at idle then drop to 0 after engine shut off.

Does the vacuum gauge indicate steady vacuum above 25 inches then drop to 0 at engine shut off?
Yes --> Go To 4
No --> Check the vacuum hose between Vacuum Res Solenoid B port and Boost Pressure Solenoid A port for damage, restrictions or leaks.
Replace as necessary. If Hose is OK., replace the Vacuum Reservoir Solenoid.
Perform ROAD TEST VERIFICATION - VER-2 .		 All
4
NOTE: The engine temperature must be above 120°F for this test to be valid.
Turn the ignition off.Disconnect the vacuum hose at the Boost Pressure Actuator connector.Connect a vacuum gauge to the disconnected hose.Start the engine.Observe and note the vacuum gauge reading.Does the vacuum gauge indicate vacuum between 15 and 22 inches?Yes --> Test Complete.No --> Check the vacuum hose between Boost Pressure Solenoid B port and Boost Pressure Actuator for damage, restrictions or leaks.Replace as necessary. If Hose is OK., replace the Boost Pressure Solenoid.Perform ROAD TEST VERIFICATION - VER-2 .		 All
5 Reconnect all vacuum hoses/lines.
Turn the ignition off.
Disconnect the vacuum hose at the Vacuum Reservoir port A connector.
Connect a vacuum gauge to the disconnected hose.
Start the engine.
Observe the vacuum gauge reading.
Does the vacuum gauge indicate steady vacuum above 25 inches?
Yes --> Check Vacuum Reservoir and Vacuum Reservoir Output Hose to Vacuum Reservoir Solenoid for damage, cracks, obstructions or other problems that may prevent proper vacuum supply to the Vacuum Reservoir Solenoid.
Perform ROAD TEST VERIFICATION - VER-2 .
No --> Check vacuum hoses from Vacuum Pump to the Vacuum Reservoir for leaks or blockage. Refer to the Service Information to check for proper Vacuum Pump operation.
Perform ROAD TEST VERIFICATION - VER-2 .		 All
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