Computer Command Control - Throttle Body Fuel Injection

EGR System Flow Chart For 2.5L, 4.3L-Except S/T, 5.0L, 5.7L, (Under 8500 GVW):

EGR System Wiring For 2.5L, 4.3L-Except S/T, 5.0L, 5.7L, (Under 8500 GVW):

EGR SYSTEM CHECK (CHART C-7)





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:

^ Engine coolant temperature - above 25~C.
^ TPS - "OFF" idle
^ MAP
If Code 24 is stored, use that chart first.

Code 32 will detect a faulty solenoid, vacuum supply, EGR Valve or plugged passage. This chart checks for plugged EGR passages, a sticking EGR valve, or a stuck open or inoperative solenoid.


TEST DESCRIPTION: Numbers below refer to circled numbers on the 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 back pressure valve should hold vacuum with engine "OFF".

5. When engine is started, exhaust back pressure should cause vacuum to bleed off and valve to fully close.


DIAGNOSTIC AIDS:

^ Before replacing ECM, use an ohmmeter and check the resistance of each ECM controlled relay and solenoid coil. Refer to ECM QDR check procedure. See ECM wiring diagram for coil term. I.D. of solenoid(s) and relay(s) to be checked. Replace any solenoid where resistance measures less than 20 ohms.