Throttle Body Fuel Injection System

Fig. 089 - Wiring Diagram for Chart C-7 EGR Check. VIN Z:

CHART C-7

EXHAUST GAS RECIRULATION (EGR) CHECK

4.3L "B/G" SERIES

FUEL INJECTION (TBI)

Circuit Description:
The ECM operates a solenoid to control the 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.

Fig. 088 Chart C-7 EGR Check:

Test Description:
Step numbers refer to step numbers on diagnostic chart.
1. Checks for solenoid stuck open.
2. Checks for solenoid always being energized.
3. Grounding test terminal should energize solenoid and vacuum should drop.
4. Negative backpressure valve should hold vacuum with engine "OFF".
5. When engine is started, exhaust backpressure should cause vacuum to bleed off and valve to fully close.
6. 4.3L engines have a manifold vacuum source which should have at least 7 Hg at idle.