DTC Descriptor
DTC P0404: Exhaust Gas Recirculation (EGR) Open Position Performance
Diagnostic Fault Information
Important: Always 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 the difference between the actual EGR position and the desired EGR position when the EGR is commanded open.
Conditions for Running the DTC
| • | The Ignition 1 Signal 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 open. |
| • | The EGR flow test is not running. |
Conditions for Setting the DTC
| • | The difference between the EGR Position Sensor parameter and the desired EGR Position parameter is more than 15 percent. |
| • | The above condition is met for more than 20 seconds. |
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp
(MIL) on the second consecutive ignition cycle that the diagnostic runs and
fails. |
| • | The control module records the operating conditions at the time
the diagnostic fails. The first time the diagnostic fails, the control module
stores this information in the Failure Records. If the diagnostic reports
a failure on the second consecutive ignition cycle, the control module
records the operating conditions at the time of the failure. The control
module writes the operating conditions to the Freeze Frame and updates
the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL)
after 3 consecutive ignition cycles that the diagnostic runs and does
not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs
and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles,
if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
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
- With the ignition ON and the engine OFF, observe the DTC information on the scan tool.
- Disconnect the EGR harness connector and observe the EGR Position Sensor parameter. The EGR Position Sensor parameter should display 0 percent.
| ⇒ | 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. |
- 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.
| ⇒ | 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. |
- 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.
| ⇒ | If the resistance is more than 3 ohms, test each circuit for high resistance. |
| ⇒ | If all circuits test normal, replace the EGR valve. |
Repair Instructions
Important: Always perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
