The control module tests the exhaust gas recirculation (EGR) system during deceleration. The control module does this by momentarily commanding the EGR valve to open while monitoring the signal circuit of the manifold absolute pressure (MAP) sensor. When the EGR valve is opened, the control module will expect to see a predetermined increase in MAP. If the expected increase in MAP is not detected, the control module records the amount of MAP difference that was detected and adjusts a calibrated fail counter towards a calibrated fail threshold level. The number of EGR flow test counts required to exceed the fail threshold may vary according to the amount of detected EGR flow error.

The EGR valve position sensor is monitored by the control module. The 5-volt reference circuit, the low reference circuit, and the EGR valve position signal circuit are used by the control module to determine the EGR valve position. The control module compares the EGR Position Sensor parameter with the desired EGR Position parameter when the valve is commanded open or closed.

The control module controls the EGR valve with a solid state device called a driver. The driver supplies the EGR solenoid with 12 volts that is pulse width modulated (PWM) through the EGR solenoid high control circuit. A ground path is provided by the control module through the EGR solenoid low control circuit. The driver has the ability to detect an electrical malfunction on the EGR solenoid control circuits.

When the ignition switch is turned ON, the control module records the EGR Learned Minimum Position. The control module compares the EGR Learned Minimum Position parameter to the EGR Position Sensor parameter.

The control module is able to determine the difference between the actual EGR position and the desired EGR position when the EGR is commanded open.

DTC P0404 is a Type B DTC.

DTC P0404 is a Type B DTC.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Description and Operation

Exhaust Gas Recirculation (EGR) System Description

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Scan Tool Data List

Important: If DTC P0405, P0406, P0641, P0651 are also set , diagnose those DTCs first.

Important: You must complete the Circuit/System Verification before proceeding with Circuit/System Testing.

1. Ignition OFF, disconnect the EGR valve harness connector.
2. Ignition ON, the EGR Position parameter should display less than 1 percent.

⇒	If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.

3. Install a 3A fused jumper wire between the signal circuit and the 5-volt reference circuit at the EGR harness connector. The EGR Position Sensor parameter should display more than 99 percent.

⇒	If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

4. Disconnect the control module and measure the resistance of the EGR high control circuit and the EGR low control circuit. Each circuit should measure less than 5 ohms.

⇒	If the resistance is more than the specified range, test each circuit for an open/high resistance.

5. If all circuits test normal, replace the EGR valve.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.