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P0404 BUICK - Exhaust Gas Recirculation Open Position Performance

Possible causes
- EGR volume control valve stuck open or closed
- Faulty EGR volume control solenoid valve
- EGR volume control solenoid valve harness is open or shorted
- EGR volume control solenoid valve circuit poor electrical connection
- EGR temperature sensor and circuit
What does this mean? What does this mean?
When is the code detected?
The PCM calculates an error based on the difference between the actual EGR position and the desired EGR position. The PCM sets the P0404 code if the error is too great.
Possible symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Possible engine hesitation
P0404 Buick Description

An Exhaust Gas Recirculation (EGR) system is used in order to lower Oxides of Nitrogen (NOx) emission levels. The EGR system accomplishes this by feeding small amounts of exhaust gas back into the combustion chamber. High combustion temperatures cause NOx. Combustion temperatures are reduced when the air/fuel mixture is diluted with the exhaust gases.

The EGR valve is designed to accurately supply exhaust gases to the engine without the use of intake manifold vacuum. The EGR valve controls the exhaust flow into the intake manifold from the exhaust manifold through an orifice with a Powertrain Control Module (PCM) controlled pintle. The PCM controls the pintle position using inputs from the Throttle Position (TP) sensor, the Manifold Absolute Pressure (MAP) sensor and, the Engine Coolant Temperature sensor. The PCM commands the EGR valve in order to supply the correct amount of exhaust gas recirculation for the current engine operating conditions.

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