Part 1 of 2

DTC 32 Chart Part 1 Of 2 Exhaust Gas Recirculation:

EGR Control Wiring Diagram:

Circuit Description:


The Exhaust Gas Recirculation (EGR) valve vacuum is controlled by an ECM controlled solenoid valve. The ECM will turn the EGR "ON" and "OFF" (Duty Cycle) by grounding CKT 435. The duty cycle is calculated by the ECM based on information from the engine coolant temperature, air flow and engine RPM. There should be no EGR when in park or neutral, TP sensor input below a specified value, or TP sensor indicating Wide Open Throttle (WOT).

With the ignition "ON" engine stopped, the EGR solenoid valve is de-energized and by grounding the diagnostic "test" terminal, the solenoid valve is energized.



The ECM will check EGR operation when:

- Vehicle speed is above 50 mph.
- Throttle angle is between 8% and 30%.
- No more than 0.4% change in throttle position.
- MAP is in the range listed below, depending on the barometric pressure (as measured by MAP sensor w/ign. "ON", engine "OFF".)

BARO PRESSURE (kPa)
100 90 80 70
________________________________

MAP 30-85 20-75 10-65 0-55
(RANGE)






Test Description: The numbers below refer to circled numbers on the diagnostic chart.

1. Intake Passage: Shut "OFF" the engine and remove the EGR valve from the manifold. Plug the exhaust side hole with a shop towel or suitable stopper. Leaving the intake hole open, attempt to start the engine. If the engine runs at a very high idle speed (up to 3000 rpm is possible) or starts and stalls, the EGR passages are not restricted. If the engine starts and idles normal, the EGR intake side passage, in the intake manifold, is restricted.
Exhaust Passage: With the EGR valve still removed, plug the intake side hole with the same stopper. With the exhaust side hole open, check for the presence of exhaust gas. If no exhaust gas is present, the EGR exhaust side passage, in the intake manifold, is restricted.

2. Grounding the diagnostic test terminal should allow the EGR solenoid to energize, and vacuum should flow to the gauge. The vacuum at the gauge may or may not bleed off slowly.

It is important that the gage is able to read the amount of vacuum being applied.

3. When the diagnostic test terminal is not grounded, the vacuum gauge should bleed off through a vent in the EGR solenoid.

4. This test determines if the electrical control portion of the system is at fault, or if the EGR solenoid and/or connector is at fault.



Diagnostic Aids:


The EGR circuit can be inoperative if the PNP switch is misadjusted or faulty. The EGR is disabled when in park or neutral. To check the PNP switch, Chart C-1A Park/Neutral Switch Diagnosis

Suction from shop exhaust hoses can alter backpressure and may affect the operation of the EGR valve during install testing.

The ECM also monitors left side short term fuel trim during a DTC 32 test and must detect a change to pass the test. If short term fuel trim is at a fixed value (lean or rich) when a DTC 32 test is run, a DTC 32 may set.

Vacuum lines should be thoroughly checked for proper routing. Vacuum source goes to orifice side of the EGR solenoid valve. Refer to "Vehicle Emissions Control Information" label.