GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provide an overview of each diagnostic category.

DTC Descriptors

DTC P0405:  Exhaust Gas Recirculation (EGR) Position Sensor Circuit Low Voltage

DTC P0406:  Exhaust Gas Recirculation (EGR) Position Sensor Circuit High Voltage

Diagnostic Fault Information

Circuit

Short to Ground

High Resistance

Open

Short to Voltage

Signal Performance

EGR 5-Volt Reference Voltage

P0107, P0698, P2564

P0102, P0401, P046C

P0405

P0106, P0699, P2227, P2565

--

EGR Sensor Signal

P0405

P0101, P0405

P0405

P0106, P0401, P0699, P2565

--

EGR Low Reference

--

P0401, P046C

P0406

--

--

EGR MTR High Control

P0403

P0401, P046C

P0403

P046C

--

EGR MTR Low Control

P0403, P046C

P0401, P046C

P0403

P0403

--

Typical Scan Tool Data

EGR Position Sensor

Circuit

Normal Range

Short to Ground

Open

Short to Voltage

Operating Conditions: Engine Running, ECT sensor is less than 60°C (140°F)

EGR 5-Volt Reference Voltage

0.98 Volts

0 Volts

0 Volts

1.29 Volts

EGR Sensor Signal

0.98 Volts

0 Volts

0 Volts

4.98 Volts

EGR Low Reference

0.98 Volts

--

4.8 Volts

--

Circuit/System Description

The engine control module (ECM) uses the exhaust gas recirculation (EGR) position sensor to determine the position of the EGR valve. The ECM sends a reference voltage through the 5-volt reference circuit to the EGR position sensor. The ECM provides a voltage return path for the sensor through the low reference circuit. A variable voltage signal, based on the EGR valve position, is sent from the sensor to the ECM through the EGR position sensor signal circuit. If the ECM detects an EGR position sensor voltage that is less than or more than the normal operating range, DTC P0405 or P0406 sets.

Conditions for Running the DTC

    • DTCs P0698 and P0699 are not set.
    • The ignition is ON.
    • This DTC runs continuously when the above conditions are met.

Conditions for Setting the DTC

P0405

The EGR position sensor voltage is less than 0.26 volt for more than 3 seconds.

P0406

The EGR position sensor voltage is more than 4.75 volt for more than 3 seconds.

Action Taken When the DTC Sets

    • DTCs P0405 and P0406 are Type B DTCs.
    • Diesel particulate filter (DPF) regeneration is inhibited.

Conditions for Clearing the DTC

DTCs P0405 and P0406 are Type B DTCs.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

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

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

  1. The EGR Position Sensor parameter is between 0.25-4.75 volts.
  2. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

  1. Ignition OFF, test for less than 1 ohm between the low reference circuit terminal B and ground.
  2. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal A and ground.
  4. If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
    If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  5. Ignition ON, and the EGR valve disconnected, observe that the EGR Position parameter on the scan tool is 0 volt.
  6. If the EGR Position parameter is more than 0 volt, test the signal circuit for a short to voltage. If the circuits test normal, replace the ECM.
  7. Ignition ON and the EGR valve disconnected, connect a jumper wire between the 5-volt reference circuit terminal A and the signal circuit terminal C and observe with a scan tool that the EGR sensor parameter displays 4.98-5.02 volts.
  8. If the EGR Sensor parameter is less than 4.98 volts, test the signal circuit for an open, short to ground, or high resistance. If the circuits test normal, replace the control module.
  9. If the circuits test normal, replace the EGR valve.

Repair Instructions

    •  Exhaust Gas Recirculation Valve Replacement
    •  Control Module References for ECM replacement, setup, and programming

Repair Verification

  1. Install any components or connectors that have been removed or replaced during diagnosis.
  2. Perform any adjustment, programming, or setup procedures that are required when a component or module is removed or replaced.
  3. Clear the DTCs.
  4. Turn OFF the ignition for 90 seconds.
  5. Duplicate the Conditions for Running the DTC and use the Freeze Frame/Failure Records, if applicable, in order to verify the DTC does not reset. If the DTC resets or another DTC is present, refer to Diagnostic Trouble Code (DTC) List - Vehicle and perform the appropriate diagnostic procedure.
  6. Perform the Diesel Particulate Filter (DPF) Service Regeneration.