Powertrain Controls - ECM/PCM

DTC 32 Chart:

EGR Circuit:

CIRCUIT DESCRIPTION
A vacuum diaphragm in the EGR valve is connected to a timed vacuum signal port in the throttle body. As the throttle valve is opened, vacuum is applied through an exposed vacuum port to the EGR control solenoid valve. This valve which is located between the throttle body and the EGR valve commands vacuum to the EGR valve based on information from the certain input sensors.

The negative backpressure EGR valve is a normally closed valve and is opened against calibrated spring tension by a negative backpressure. If there is little or no vacuum in the diaphragm chamber from the timed vacuum supply, like idle or wide open throttle, the EGR valve will not open. However, if there is sufficient vacuum in the chamber, the pintle rises off its seat opening the EGR valve and allowing EGR to enter into the intake manifold.

When the EGR valve opens allowing EGR, the backpressure is reduced by interaction with manifold vacuum and creates a slight vacuum. This vacuum opens a control valve bleeding the vacuum from the diaphragm chamber causing the EGR valve to close.


DTC 32 WILL SET WHEN
The PCM does not see a change in MAP when EGR test is executed, based on current BARO value under the following conditions:
- Manifold vacuum is between 33 and 60 kPa.
- TCC is locked.
- VSS is greater than 40 mph.
- DTC(s) 21, 22, 33, or 34 is not set.

ACTION TAKEN (PCM WILL DEFAULT TO)
The Malfunction Indicator Lamp (MIL) will illuminate, the EGR system will go into "Open Loop," and the cooling fan will enable.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. Intake passage: Shut the engine "OFF" and remove the EGR valve from the manifold. Plug the exhaust side hole with a suitable stopper. Leaving the intake side hole open, attempt to start the engine. If the engine runs at a high idle (up to 3000 RPM is possible) or starts and stalls, the EGR intake passage is not restricted. If the engine starts and idles normally, the EGR intake passage is restricted. Exhaust passage: With EGR valve still removed plug the intake side hole with a suitable 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 is restricted.
2. The remaining test checks the ability of the EGR valve to interact with the exhaust system. This system uses a negative backpressure EGR valve which should hold vacuum with engine "OFF." BE SURE SHOP EXHAUST HOSE IS NOT CONNECTED DURING STEPS 2 AND 3.
3. When the engine is started, exhaust backpressure at the base of the EGR valve should open the valve's internal bleed and vent the applied vacuum allowing the valve to seat. BECAUSE THE SHOP EXHAUST HOSE IS NOT INSTALLED AT THIS TIME. DO NOT ALLOW THE ENGINE TO RUN LONGER THAN 15 SECONDS.

DIAGNOSTIC AIDS
- Vacuum lines should be thoroughly checked for proper routing. Refer to "Vehicle Emission Control Information" label.
- If problems continue, refer to Exhaust Gas Recirculation to diagnose EGR system. Exhaust Gas Recirculation