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 P0403: Exhaust Gas Recirculation (EGR) Solenoid Control Circuit

DTC P0489: Exhaust Gas Recirculation (EGR) Solenoid Control Circuit Low Voltage

DTC P0490: Exhaust Gas Recirculation (EGR) Solenoid Control Circuit High Voltage

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Ignition 1 Voltage

P0340, P0342, P0458, P0489

P0403

--

--

Solenoid Control

P0406, P0489

P0403

P0490

P0404

5-Volt Reference

P0106, P0405, P2122, P2138

P0405

--

--

EGR Position Sensor Signal

P0405

P0405

P0406

P0404

Low Reference

--

P0406

--

--

Typical Scan Tool Data

EGR Position Sensor

Circuit

Short to Ground

Open

Short to Voltage

Operating Conditions: Engine operating in Closed Loop

Parameter Normal Range: 0-4%

Ignition 1 Voltage

--

--

--

Solenoid Control

99%

--

--

5-Volt Reference

0%

0%

99%¹

EGR Position Sensor Signal

0%

0%

99%¹

Low Reference

--

0%

--

¹ Internal ECM damage may occur if the circuit is shorted to B+.

Circuit Description

Voltage is provided to the exhaust gas recirculation (EGR) valve by the ignition 1 voltage circuit through a fuse. Ground is provided to the EGR valve on the control circuit by a low side driver within the engine control module (ECM). The ECM monitors the voltage on the control circuit of the EGR valve to determine if a failure is present.

The ECM monitors the position of the EGR valve through the EGR valve position sensor. The EGR valve position sensor sends a feedback voltage on the signal circuit to the ECM. The EGR position sensor voltage varies depending on the position of the EGR valve.

The EGR valve utilizes the following circuits:

    • An ignition 1 voltage circuit
    • A control circuit
    • A 5-volt reference circuit
    • A signal circuit
    • A low reference circuit

Conditions for Running the DTC

    • The engine is running.
    • The DTCs run continuously when the above condition is met.

Conditions for Setting the DTC

P0403

The ECM detects an open on the EGR solenoid control circuit.

P0489

The ECM detects a short to ground on the EGR solenoid control circuit.

P0490

The ECM detects a short to voltage on the EGR solenoid control circuit

Action Taken When the DTC Sets

DTC P0403, P0489, and P0490 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTC P0403, P0489, and P0490 are Type B DTCs.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

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

Description and Operation

Exhaust Gas Recirculation (EGR) System Description

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

    •  Scan Tool Data List
    •  Scan Tool Data Definitions
    •  Scan Tool Output Controls

Circuit/System Verification

  1. Ignition ON, observe the scan tool Actual EGR position parameter while commanding the EGR valve ON and OFF. The reading should change from 0 percent to 99 percent with each command.
  2. If the vehicle passes the Circuit/System Verification test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records List.

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the EGR valve.
  2. Ignition ON, verify a test lamp illuminates between the ignition 1 voltage circuit and ground.
  3. If the test lamp does not illuminate, test the ignition 1 voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition 1 voltage circuit fuse is open, test all components connected to the ignition 1 voltage circuit and replace as necessary.
  4. Ignition OFF, verify a test lamp does not illuminate between the control circuit and B+.
  5. If test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.
  6. Ignition ON, command the EGR valveON and OFF with a scan tool, The test lamp should illuminate.
  7. If test lamp does not illuminate, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
  8. If all circuits test normal, test or replace the EGR valve.

Component Testing

  1. Ignition OFF, disconnect the harness connector at the EGR valve.
  2. Test for 6-10 ohms of resistance between the ignition 1 voltage circuit terminal and the control circuit terminal of the EGR valve.
  3. If not within the specified range, replace the EGR valve.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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