*CHECKING THE EGR SYSTEM
For a complete wiring diagram Refer to Section 8W
| Possible Causes |
| VACUUM HOSES/TUBES |
| VACUUM SUPPLY SYSTEM |
| EGR VALVE |
| VALVE BLOCK ASSEMBLY |
1. CHECKING VACUUM AT EGR VALVE
NOTE: Ensure there are no EGR hardwire/circuit related DTC's before continuing. Existing EGR circuit related faults will cause misdiagnosis during this test.
Turn the ignition off.
Disconnect the EGR Valve vacuum supply hose.
Connect a vacuum gauge to the disconnected EGR Valve vacuum supply hose.
While observing the vacuum gauge, start and idle the engine
NOTE: The vacuum reading should be above 16 inches for 2 minutes after engine start then drop to below 2 inches.
Does the vacuum read above 16 inches for 2 minutes then drop to below 2 inches?
Yes
- Go to 2
No
- Go to3
- Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)
2. EGR VALVE
| INCHES OF VACUUM APPLIED TO EGR VALVE | MAF PER CYLINDER MG/HU |
| 10 | 435 — 475 |
| 15 | 255 — 295 |
| 20 | 165 — 215 |
NOTE: The engine temperature must be above 160°F for this test to be valid.
Turn the ignition off.
Disconnect the vacuum supply hose from the EGR Valve.
Connect a vacuum pump to the EGR Valve vacuum port.
Start the engine.
NOTE: Engine must be idling in park.
Apply 10 inches, 15 inches and 20 inches of vacuum to the EGR Valve and note the MAF readings at each of the applied vacuum steps.
NOTE: An engine tone change should also be heard when 15 inches or more vacuum is applied to the EGR Valve.
Refer to the chart and compare each of the MAF readings for each of the applied vacuum steps
Are the MAF Per Cylinder mg/hu within the chart specifications for applied vacuum step?
Yes
- EGR system functioning properly. Test complete.
No
- Replace the EGR Valve.
3. CHECKING VACUUM AT VALVE BLOCK ASSEMBLY
Turn the ignition off.
Disconnect the Valve Block vacuum hose connector.
Connect a vacuum gauge to the vacuum supply port of the disconnected Valve Block vacuum hose connector. Vacuum supply is provided via the Blue colored vacuum tube at the valve Block vacuum hose connector.
While observing the vacuum gauge, start and idle the engine
NOTE: The vacuum reading should be above 22 inches with the engine idling.
Does the vacuum read above 22 inches with the engine idling?
Yes
- Go To 4
No
- Repair vacuum supply system for insufficient vacuum.
- Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)
4. CHECKING THE AIR CLEANER VENT HOSE
Turn the ignition off.
Disconnect the Valve Block vacuum hose connector.
Check the Black colored vacuum hose between the Valve Block hose connector and the air cleaner for kinks, debris or other restrictions.
NOTE: Problems with this hose will cause incorrect vacuum to the EGR Valve resulting in driveability problems.
Were any problems found?
Yes
- Repair or replace as necessary.
No
- Go to 5
- Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)
5. CHECKING THE EGR VACUUM SUPPLY HOSE
Turn the ignition off.
Disconnect the Valve Block vacuum hose connector.
Check the Tan colored vacuum hose between the Valve Block hose connector and the EGR Valve for kinks, debris or other restrictions.
NOTE: Problems with this hose will cause incorrect vacuum to the EGR Valve resulting in driveability problems.
Were any problems found?
Yes
- Repair or replace as necessary.
No
- Replace the Valve Block Assembly.
- Perform the ECM Verification Test Ver. 1. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)