Exhaust Gas Recirculation (EGR) System Description. Pontiac Bonneville 2004

For 1990-2009 cars only

Makes 🢒 Pontiac 🢒 2004 🢒 Bonneville 🢒 Engine 🢒 Engine Controls - 4.6L 🢒 Exhaust Gas Recirculation (EGR) System Description

Exhaust Gas Recirculation (EGR) System

The Exhaust Gas Recirculation (EGR) System is used to reduce the amount of nitrogen oxide (NOx) emission levels caused by high combustion temperatures. At temperatures above 1 371°C (2,500°F), oxygen and nitrogen combine to form oxides of NOx. Introducing small amounts of exhaust gas back into the combustion chamber displaces the amount of oxygen entering the engine. With less oxygen in the air/fuel mixture, the combustion pressures are reduced and, as a result, combustion temperatures are decreased restricting the formation of NOx. The EGR system will only operate under specific temperature, barometric pressure and engine load conditions in order to prevent driveability concerns and to increase engine performance.

Linear EGR Valve


(1)	Cap-Sensor
(2)	Sensor-EGR Pintle Position
(3)	Pole Piece-Primary
(4)	Bobbin and Coil Assembly
(5)	Sleeve-Armature
(6)	Valve-Pintle
(7)	Armature and Base Assembly

Linear EGR Control

The linear exhaust gas recirculation (EGR) valve is controlled by a high side driver within the powertrain control module (PCM) The high side driver provides 12 volts that is pulse width modulated (PWM) by a duty cycle via the high control circuit of the EGR valve . The ground path is provided by the low control circuit of the EGR valve. The PCM calculates the amount of EGR needed based on the following inputs:

•	The engine coolant temperature (ECT) sensor

•	The intake air temperature (IAT) sensor

•	The barometric pressure (BARO)

•	The manifold absolute pressure (MAP) sensor

•	The throttle position (TP) sensor

•	The mass air flow (MAF) sensor

EGR Diagnostics

The PCM tests the exhaust gas recirculation (EGR) flow during deceleration by momentarily commanding the EGR valve to open while monitoring the signal of the manifold absolute pressure (MAP) sensor. When the EGR valve is opened, the PCM will expect to see a predetermined increase in MAP. If the expected increase in MAP is not detected, the PCM records the amount of MAP difference that was detected and adjusts a calibrated fail counter towards a calibrated fail threshold level. When the fail counter exceeds the fail threshold level, the PCM will set a diagnostic trouble code (DTC).

Normally, the PCM will only allow one EGR Flow Test Count during an ignition cycle. To aid in verifying a repair, the PCM allows 12 EGR Flow Test Counts during the first ignition cycle following a code clear or a battery disconnect. Between 9-12 EGR Flow Test Counts should be sufficient for the PCM to determine adequate EGR flow and pass the EGR flow test. If the PCM detects an EGR flow error, a DTC will set.

The PCM monitors the position of the EGR valve pintle via the EGR position sensor. If the PCM detects a calibrated variance between the Desired EGR Position parameter and the EGR Position Sensor parameter, actual position, for a calibrated amount of time a DTC will set.

The PCM also monitors the EGR solenoid high control circuit EGR solenoid low control circuit for electrical faults. If an EGR control circuit fault is detected for a calibrated amount of time a DTC will set.