Exhaust Gas Recirculation: Testing and Inspection

EGR System Component Locations (California):

IMPORTANT: Engine temperature must be below 59° F (15° C) to accurately perform the following inspection procedure.

1. Connect a tachometer to engine.
2. Disconnect the Vacuum hose leading to the EGR valve.
3. Connect a vacuum to the end of EGR hose.
4. Lift rear wheels and support with stands.
5. Start engine and confirm that vacuum does not exist at EGR hose at all engine speeds.
^ This confirms that the ECU is not energizing the VSV, which would allow the EGR to operate when the engine is cold. If vacuum does exist, check the wiring between the VSV and ECM. If no faults are found, proceed to COMPUTERS AND CONTROL SYSTEMS / ON-BOARD DIAGNOSTICS and check for DTCs.
6. Allow the engine to warm to operating temperature.
7. Check that vacuum does not exist at idle.
^ If vacuum does exist at idle, check vacuum hoses for correct connections.
8. Raise the engine speed to 3500 rpm and confirm that vacuum rises.
^ If vacuum does not rise, check the following:
- Throttle chamber for restriction
- Vacuum tank
- Vacuum regulator
- Duty solenoid
- VSV
- DTC's
9. Connect a hand vacuum pump to the EGR valve fitting.
10. With the engine at idle, apply vacuum to the EGR valve.
^ The diaphragm should not leak vacuum and the engine should run poorly or stall. If the diaphragm does not hold vacuum, replace EGR valve.
If the engine operation did not change, check the following:
- Stuck EGR Valve
- Restricted EGR passage
11. Reconnect the hose to the EGR valve.
12. Confirm that EGR valve diaphragm operates smoothly when raising and lowering engine speed.