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
DTC P042E: Exhaust Gas Recirculation (EGR) Closed Position Performance

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Ignition 1 Voltage | * | P0403, P0405 | -- | P0404, P042E
Solenoid Control | P0402 | P0403, P0404 | P0403, P0404 | P0404, P042E
5-Volt Reference | P0107, P0405, P0452, P0651, P2077, P2106 | P0405 | P0107, P0446, P0453, P0651, P2106 | --
EGR Position Sensor Signal | P0405 | P0405 | P0406 | P0404, P042E
Low Reference | -- | P0406 | -- | --
* 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%*
EGR Position Sensor Signal | 0% | 0% | 99%*
Low Reference | -- | 0% | --
* 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

#### P0403, P0404, and P042E

• | DTCs P0112, P0113, P0405, P0406, P0502, P0562, and P0563 are not set.

• | The engine is running.

• | The intake air temperature (IAT) is between 3-80°C (37-176°F).

• | The ignition voltage is between 11-16 volts.

• | The Desired EGR position is greater than 0 percent and does not change more than 3 percent - DTC P0404 only.

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

#### P0405 and P0406

• | The engine is running.

• | The ignition voltage is between 11-16 volts.

• | The DTC runs continuously when 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 a difference between the actual EGR position and the commanded EGR position of more than 15 percent.

#### P0405

The ECM detects that the EGR position sensor percentage is less than 2 percent.

#### P0406

The ECM detects that the EGR position sensor percentage is greater than 98 percent.

#### P042E

The ECM detects the difference between the actual EGR position and the learned EGR position is greater than 10 percent.

### Action Taken When the DTC Sets

• | DTCs P0403, P0405, and P0406 are Type A DTCs.

• | DTCs P0404 and P042E are Type B DTCs.

### Conditions for Clearing the DTC

• | DTCs P0403, P0405, and P0406 are Type A DTCs.

• | DTCs P0404 and P042E are Type B DTCs.

### Diagnostic Aids

• | If a shared 5-volt reference circuit is shorted to ground or shorted to a voltage, other 5-volt reference circuits may be affected.

• | The scan tool 5-volt reference parameter should display between 4.8-5.2 volts.

### 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 DTC information with a scan tool. Verify DTC P0651 is not set.

⇒ | If DTC P0651 is set, refer to DTC P0641 or P0651 .

2. Ignition ON, observe the EGR Position Variance parameter while commanding the EGR valve to a 100 percent. The reading should be less than 15 percent.
3. Engine running, observe the EGR position sensor percentage parameter. The reading should be less than 4 percent.
4. 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 Data List.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector of the EGR valve.
2. Ignition ON, verify that a test lamp illuminates between the ignition 1 voltage circuit 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.

3. Ignition OFF, verify a test lamp does not illuminate between the control circuit and B+.

⇒ | If test lamp illuminates, test the control circuit for a short to ground. If the circuit/connections test normal, replace the ECM.

4. Ignition ON, With a scan tool, command the EGR valve to 100 percent. The test lamp should illuminate.

⇒ | If test lamp does not illuminate, test the control circuit for a short to voltage or an open/high resistance. If the circuit/connections test normal, replace the ECM.

5. Ignition OFF, test for less than 1 ohm of resistance between the low reference circuit and ground.

⇒ | If greater than the specified value, test the low reference circuit for an open/high resistance. If the circuit/connections test normal, replace the ECM.

6. 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/connections test normal, replace the ECM.

⇒ | If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit/connections test normal, replace the ECM.

7. Ignition ON, verify that the EGR position sensor parameter is less than 3 percent.

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

8. Ignition ON, install a 3-amp fused jumper wire between the signal circuit and the 5-volt reference circuit. Verify that the EGR position sensor parameter is greater than 95 percent.

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

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

### Component Testing

1. Ignition OFF, disconnect the harness connector of the EGR valve.
2. Measure for 6-10 ohms of resistance between the ignition 1 voltage and control circuit terminal of the EGR valve.

⇒ | If the resistance is out of 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 engine control module replacement, setup, and programming