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 provide an overview of each diagnostic category.

### DTC Descriptors

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 | 1 | P0403 | -- | P0404
Solenoid Control | P0489 | P0403 | P0490 | P0404
5-Volt Reference | P0107, P0405 | P0405 | -- | --
EGR Position Sensor Signal | P0405 | P0405 | P0406 | P0404
Low Reference | -- | P0406 | -- | --
1. Engine cranks but does not run and the fuse for the ignition 1 circuit opens.

### 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 ignition voltage is between 10-16 volts.

• | The engine fuel-cutoff is disabled - P0404 only.

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

### Conditions for Setting the DTC

#### P0404

The ECM detects a difference between the actual EGR position and the commanded EGR position of more than 20 percent.

#### P0405

The ECM detects that the EGR position sensor voltage is less than 1 volt.

#### P0406

The ECM detects that the EGR position sensor voltage is greater than 4.7 volts.

### Action Taken When the DTC Sets

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

### Conditions for Clearing the MIL/DTC

DTC P0404, P0405, and P0406 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. Test for less than 10 ohms of resistance between the low reference circuit 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.

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.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit 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.

4. Ignition ON, verify the scan tool EGR position sensor parameter is less than 3 percent.

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

5. Ignition ON, install a 3A fused jumper wire between the signal circuit and the 5-volt reference circuit. Verify the scan tool Actual EGR position parameter is greater than 95 percent.

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

6. If all circuits test normal, 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