DTC Descriptor
DTC P0405: Exhaust Gas Recirculation (EGR) Position Sensor Circuit Low Voltage
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 if the EGR valve position sensor signal voltage is too low.
Conditions for Running the DTC
| • | The EGR command will be disabled if the start-up ECT is less than 5°C (41°F) and will not enable until the ECT is more than 75°C (167°F). |
| • | The EGR flow test is not running. |
| • | The Ignition 1 Signal parameter is more than 11 volts. |
Conditions for Setting the DTC
| • | The EGR Position Sensor parameter is less than 0.35 volt. |
| • | 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 measure the EGR 5-volt reference circuit for 4.8-5.2 volts.
| ⇒ | If the voltage is less than 4.8 volts test the EGR valve 5-volt reference circuit for an open, high resistance, a short to ground, or a short to the EGR low control circuit. If the circuit tests normal, replace the control module. |
| ⇒ | If the voltage is more than 5.2 volts test the EGR valve 5-volt reference circuit for a short to voltage or a short to the EGR high control circuit. |
- Using a 3-amp fused jumper wire connect the EGR valve 5-volt reference circuit to the EGR position signal circuit and observe the EGR position sensor parameter for more than 4.9 volts.
| ⇒ | If the EGR Position Sensor parameter is less than 4.9 volts test the EGR Position Signal circuit for an open or high resistance or a short to ground. If the circuit tests normal, replace the control module. |
- Using a 3-amp fused jumper wire connect the EGR high control circuit to the EGR low control circuit at the EGR harness connector. Command the EGR valve to 10 percent while monitoring the EGR Position Sensor parameter. The EGR Position
Sensor parameter should remain at 0 percent.
| ⇒ | If the EGR Position Sensor parameter is more than 0 percent test the EGR position signal circuit for a short to the EGR high control circuit. |
| ⇒ | If all circuits test normal, replace the EGR valve. |
Repair Instructions
Important: Always perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
