GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2006 🢒 Terraza Ext. 🢒 Brakes 🢒 Park Brake 🢒 DTC P1404

DTC Descriptor

DTC P1404: Exhaust Gas Recirculation (EGR) Closed Position Performance

Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Circuit Description

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 that the EGR valve is still open when the control module is commanding the EGR valve closed.

Conditions for Running the DTC
    • The Ignition 1 Signal voltage parameter is more than 11 volts.
    • The EGR command will be disabled if the start-up engine coolant temperature (ECT) is less than 5°C (41°F), and will not enable until the ECT is more than 75°C (167°F).
    • The EGR valve is commanded to 0 percent for 20 seconds after the EGR valve has been commanded to open more than 40 percent for 0.5 second.
    • The EGR flow test is not running.

Conditions for Setting the DTC
    • The EGR Position Sensor parameter is 0.23 volt more than the EGR Learned Minimum Position parameter when the Desired EGR Position parameter is commanded to 0 percent for 20 seconds.
    • The EGR Position Sensor parameter is more than 40 percent and is steady for 0.5 second after a test failure and before the next test will be run.
    • The above conditions are met 4 times.

Action Taken When the DTC Sets

DTC P1404 is a Type B DTC.

Conditions for Clearing the MIL/DTC

DTC P1404 is a Type B DTC.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Powertrain Control Module Connector End Views
    •  Engine Controls Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Scan Tool Data List

Diagnostic Aids

Inspect for excessive deposits on the EGR valve pintle or seat. Remove the EGR valve and inspect for deposits that may interfere with the EGR valve pintle extending completely or cause the pintle to stick.

Circuit/System Verification

With the ignition ON and the engine OFF, command the EGR from 0-100 percent. The EGR Position Sensor parameter should remain within 3 percent of the Desired EGR Position parameter.

Circuit/System Testing
  1. With the ignition ON and the engine OFF, observe the DTC information on the scan tool.
    2. ⇒If DTC P0641 is also set, diagnose those DTCs first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle .
  2. Start the engine and observe the EGR Position parameter. The EGR Position parameter should be less than 1 percent.
  3. Disconnect the EGR harness connector and observe the EGR Position Sensor parameter. The EGR Position Sensor parameter should display 0 percent.
    4. ⇒If the EGR Position Sensor parameter is more than 0 percent, test the EGR position sensor signal circuit for a short to voltage. If the circuit tests normal, replace the control module.
  4. Command the EGR valve from 0-100 percent with a scan tool, and observe the EGR Position Variance parameter. The EGR Position Variance parameter should be less than 15 percent.
    5. ⇒If the EGR Position Variance parameter is more than 15 percent, test the EGR 5-volt reference circuit and the EGR low reference circuit for an open or high resistance. If the circuit tests normal, replace the control module.
  5. Using a 3-amp fused jumper wire, jumper the EGR 5-volt reference circuit to the EGR position sensor signal circuit at the EGR harness connector and monitor the EGR Position Sensor parameter. The EGR Position Sensor parameter should display 99 percent.
    6. ⇒If the EGR Position Sensor parameter is less than 99 percent, test for an open, high resistance, or a short to ground in the EGR pintle position signal circuit. If the circuit tests normal, replace the control module.
  6. Disconnect the control module and measure the resistance of the EGR high control circuit and the EGR low control circuit. There should be less than 3 ohms of resistance on each circuit.
    7. ⇒If the resistance is more than 3 ohms, test each circuit for high resistance.
    ⇒If all circuits test OK, replace the EGR valve.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Exhaust Gas Recirculation Valve Replacement