Exhaust Gas Recirculation: Testing and Inspection

Fig. 090 Chart C-7 EGR Check:

Fig. 091 - Wiring Diagram for Chart C-7 EGR Check. VIN Z:

CHART C-7 EXHAUST GAS RECIRCULATION (EGR) CHECK

Circuit Description:
The ECM operates a solenoid to control exhaust gas recirculation (EGR) valve. This solenoid is normally closed. By providing a ground path, the ECM energizes the solenoid which then allows vacuum to pass to the EGR valve. The ECM control of the EGR is based on the following inputs:
a. Engine coolant temperature - above 25°C.
b. TPS-off idle
c. MAP
If Code 24 is stored, use that chart first.





Test Description: Numbers below refer to circled numbers on the diagnostic chart.
1. By grounding the diagnostic terminal, the EGR solenoid should be energized and allow vacuum to be applied to the EGR valve and the vacuum should hold.
2. When the diagnostic terminal is ungrounded, the vacuum to the EGR valve should bleed off through a vent in the solenoid and the valve should close. The gage may or may not bleed off but this does not indicate a problem.
3. This test will determine if the electrical control part of the system is at fault or if the connector or solenoid is at fault.
4. This system uses a negative backpressure valve which should hold vacuum with engine "OFF".
5. When engine is started, exhaust backpressure should cause vacuum to bleed off and valve should fully close.

Diagnostic Aids:
Vacuum lines should be thoroughly checked for internal restrictions. The ECM uses the MAP sensor for checking EGR operation. If there is a question of MAP sensor accuracy use CHART C-1D MAP output check
If no problems are found refer to "Intermittents"