Exhaust Gas Recirculation: Testing and Inspection

EGR System:

***UPDATED BY TSB NO. 9003006, JUNE 7, 1990
***UPDATED BY TSB NO. 9103001, JANUARY 3, 1991

EGR TEMPERATURE SENSOR

If a malfunction in the EGR temperature sensor occurs, the ECM will set a code 32 or 34. For detailed EGR temperature sensor testing procedure, see COMPUTERIZED ENGINE CONTROLS. For a resistance test, proceed as follows:
1. Remove EGR temperature sensor from vehicle.
2. Immerse sensing end in a pan of oil.
3. Connect an ohmmeter across sensor electrical terminals and use an appropriate thermometer to measure oil temperature.
4. Heat oil and compare temperature and ohmmeter readings with chart.
5. If measured resistance deviates from the specified range, replace EGR temperature sensor.

Temperature ~C(~F) Approx. K Ohms

0 (32) 27.0
20 (68) 12.1
40 (109) 5.9
80 (176) 1.7
100 (212) 1.0

EGR VALVE TESTING

1. Depress valve diaphragm to see that it operates smoothly through its full stroke.
2. Depress valve diaphragm with engine idling. Idle should become rough when diaphragm is depressed and smooth out when diaphragm is released.
3. Replace valve if it fails either of these tests.

Back Pressure Transducer Testing:

BACK PRESSURE TRANSDUCER (BPT) TESTING

1. Disconnect vacuum hoses at opposite sides of BPT.
2. Blow air into bottom (exhaust gas pressure) port of BPT and ensure that air does not flow through BPT.
3. Blow into EGR valve side of BPT and ensure air passes through BPT and out air filter.
4. Replace BPT if it fails this test.

Thermal Vacuum Valve Testing:

THERMAL VACUUM VALVE (TVV) TESTING

1. Remove TVV from vehicle.
2. Immerse sensing portion of TVV in cool water below 35~C (95~F).
3. Blow into hose to ensure that valve is closed.
4. Immerse sensing portion of TVV in hot water above 54~C (129.2~F).
5. Attach a hose to the TVV and blow to ensure the valve is open.
6. Replace TVV if it fails this test.