For 1990-2009 cars

### 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 provides an overview of each diagnostic category.

### DTC Descriptors

DTC P0403: Exhaust Gas Recirculation (EGR) Solenoid Control Circuit
DTC P0404: Exhaust Gas Recirculation (EGR) Open Position Performance
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 | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Ignition 1 Voltage | P0403 | -- | -- | P0400, P0402,
Solenoid Control | P0403 | -- | P0403 | P0400, P0402,
5-Volt Reference Voltage | P0107, P0404, P0405 | P0404, P0405 | -- | P0400, P0402,
EGR Position Sensor Signal | P0403, P0405 | P0404, P0406 | P0404, P0406 | P0400, P0402,
Low Reference |  | P0404, P0406 | -- | P0400, P0402,

### 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: 0.60-0.80 Volts
Ignition 1 Voltage | 0.71 Volts | -- | --
EGR Solenoid Control | 3.78 Volts | -- | --
5-Volt Reference | 0.71 Volts | 0.01 Volts | 1.56 Volts
EGR Position Sensor Signal | 0.01 Volts | 5.00 Volts | 5.00 Volts
Low Reference | -- | 5.00 Volts | *
* Internal ECM damage may occur if the circuit is shorted to B+.

### Circuit/System 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.

### Conditions for Running the DTC

#### P0403, P0405, and P0406

• | The ignition is ON or the engine is running.

• | The DTCs run continuously once the above conditions are met.

#### P0404

• | DTCs P0400, P0401, P0402, P0403, P0405, and P0406 are not set.

• | The engine is running.

• | Engine speed is between 2,048-2,304 RPM.

• | The mass air flow is between 20-60 percent.

• | Engine coolant temperature is greater than 70°C (158°F).

• | The DTC runs continuously once the above conditions are met.

### Conditions for Setting the DTC

#### P0403

The ECM detects an open, short to ground or voltage on the control circuit of the EGR valve.

#### P0404

The ECM detects the learned value of the EGR position sensor is less than 0.16 volt or greater than 4.90 volts.

#### P0405

The ECM detects the EGR position sensor is less than 0.10 volt.

#### P0406

The ECM detects the EGR position sensor is greater than 4.90 volts.

### Action Taken When the DTC Sets

DTC P0403, P0404, P0405, and P0406 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTC P0403, P0404, P0405, and P0406 are Type B DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component 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

Control Module References for scan tool information

### Circuit/System Verification

1. Ignition ON, observe the scan tool EGR position sensor parameter. The reading should be between the 0.60-0.80 volts.
2. Command the EGR valve ON with a scan tool. The EGR position sensor voltage should fluctuate between 0.60-3.70 volts for 3-5 seconds.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. 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, disconnect the harness connector at the EGR valve.
2. Ignition OFF, test for less than 1 ohm of resistance between the low reference circuit terminal 2 and ground.

⇒ | 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, verify that a test lamp illuminates between the ignition 1 voltage circuit terminal 5 and ground.

⇒ | 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. Connect a test lamp between the ignition 1 voltage circuit terminal 5 and the control circuit terminal 1.
5. Command the EGR solenoid ON with a scan tool. The test lamp should turn ON and OFF for 3-5 seconds.

⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If circuit tests normal, replace the ECM.

⇒ | If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If circuit tests normal, replace the ECM.

Important: The 5-volt reference circuits are internally and externally connected at the ECM. Other component DTCs may be set. If other DTCs are set, review the electrical schematic and diagnose the applicable circuits and components.

6. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 4 and ground.

⇒ | If less than the specified range, test the 5-volt reference circuit for a short to ground or 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.

7. Verify the scan tool EGR position sensor parameter is greater than 4.90 volts.

⇒ | If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.

8. Install a 3A fused jumper wire between the signal circuit terminal 3 and the low reference circuit terminal 2. Verify the scan tool EGR position sensor parameter is less than 0.2 volt.

⇒ | If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

9. If all circuits test normal, test or replace the EGR valve.

### Component Testing

1. Ignition OFF, disconnect the harness connector at the EGR valve.

Important: The EGR must be near 20°C (68°F) in order for an accurate measurement.

2. Test for 7.8-8.6 ohms of resistance between the ignition 1 voltage terminal 5 and the control terminal 1.

⇒ | 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