Powertrain Controls - ECM/PCM

DTC 32 - Exhaust Gas Recirculation Flow Check:

EGR Solenoid Wiring Circuit:

Circuit Description:
A properly operating EGR system will directly affect the air/fuel mixture requirements of the engine. Since the exhaust gas introduced into the air/fuel mixture cannot be used in combustion (contains very little oxygen), less fuel is required to maintain a correct air/fuel ratio. If the EGR system were to fail in a closed position, the exhaust gas would be replaced with air, and the air/fuel mixture would be leaner. The PCM would compensate for the lean condition by adding fuel, resulting in higher long term fuel trim values.

The fuel control on this engine is conducted within the fuel trim cells. Since EGR is not used at idle, the idle cell would not be affected by EGR system operation. The other fuel trim cells are affected by EGR operation, and, when the EGR system is operating properly, the long term fuel trim values in all cells should be close to each other. If the EGR system becomes inoperative, the long term fuel trim values in the open throttle cells would change to compensate for the resulting lean or rich mixtures, but the long term fuel trim value in the closed throttle cell would not change.

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 (A/T).
^ 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 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 (EGR) System," to diagnose EGR system. Chart C-7 EGR System Check