EGR Backpressure Transducer: Testing and Inspection
The first part of this test will determine if the transducer diaphragm at the back-pressure side of the valve has ruptured or is leaking.The second part of the test will determine if engine vacuum (full manifold) is flowing from the inlet to the outlet side of the valve.
This is not to be used as a complete test of the EGR system.
1. Disconnect the rubber back-pressure hose from the fitting at the bottom of the EGR Valve.
2. Connect a hand-held vacuum pump to this fitting.
3. Apply 10 inches of vacuum to this fitting.
4. If vacuum falls off, the valve diaphragm is leaking.
5. Replace the complete EGR valve assembly. Proceed to next step for further testing.
6. Reconnect hose to EGR valve.
7. Remove the vacuum hose at the vacuum inlet fitting on the EGR solenoid.
8. Connect a vacuum gauge to this disconnected hose.
9. Start the engine and bring to operating temperature. Hold engine speed at approximately 1,500 rpm.
10. Check for steady engine vacuum (full manifold) at this hose.
11. If engine vacuum is not present, check vacuum line to engine and repair as necessary before proceeding to next step.
12. Connect the hose to the vacuum inlet fitting on the EGR valve.
13. Disconnect the rubber hose at the vacuum outlet fitting on the EGR valve.
14. Connect a vacuum gauge to this fitting.
15. Disconnect the electrical connector from the solenoid. This will simulate an open circuit.
16. Start the engine and bring to operating temperature.
- Hold the engine speed at approximately 2,000 rpm while checking for vacuum (full manifold) at this fitting.
- As temporary back-pressure is built, full manifold vacuum should be observed at the outlet fitting.
- Without back-pressure, and engine at approximately 2,000 rpm, the gauge reading will be low. This low reading is normal.
- At idle speed, the gauge reading will be erratic. This is also normal.
17. If full manifold vacuum is not present at the outlet fitting, but was present at the inlet fitting, replace the transducer and EGR valve assembly. Refer to EGR Valve Replacement.