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 P1476: Exhaust Gas Recirculation (EGR) Solenoid Control Circuit Short to Voltage
DTC P1477: Exhaust Gas Recirculation (EGR) Solenoid Control Circuit Short to Ground
DTC P1478: Exhaust Gas Recirculation (EGR) Solenoid Control Circuit Open

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Ignition 1 Voltage | P1478 | P1478 | -- | --
Exhaust Gas Recirculation (EGR) Control Circuit | P1477 | P1478 | P1476 | --

### Circuit/System Description

Voltage is provided to the exhaust gas recirculation (EGR) solenoid 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 energizes the solenoid which allows vacuum to pass to the EGR valve. The ECM monitors the voltage on the control circuit of the EGR valve to determine if a failure is present.

### Conditions for Running the DTC

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

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

### Conditions for Setting the DTC

#### P1476

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

#### P1477

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

#### P1478

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

### Action Taken When the DTC Sets

DTCs P1476, P1477, and P1478 are Type C DTCs.

### Conditions for Clearing the DTC

DTCs P1476, P1477, and P1478 are Type C 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, command the EGR solenoid ON with a scan tool. You should hear an audible click for about 3-5 seconds.
2. 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 solenoid.
2. Ignition ON, command the fuel pump relay ON with a scan tool. Test for battery voltage between the ignition 1 voltage circuit terminal 2 and ground.

⇒ | If less than B+, repair the ignition 1 voltage circuit for a short to ground or an open/high resistance.

3. Ignition OFF, connect a test lamp between the control circuit terminal 1 and the ignition 1 voltage circuit terminal 2.
4. Ignition ON, command the EGR solenoid ON and OFF with a scan tool. The test lamp should turn ON and OFF.

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

5. If all circuits test normal, test or replace the EGR solenoid.

### Component Testing

1. Ignition OFF, disconnect the harness connector at the EGR solenoid.
2. Test for 24-28 ohms of resistance between the ignition 1 voltage terminal 2 and the control terminal 1.

⇒ | If not within the specified range, replace the EGR solenoid.

3. Test for infinite resistance between each terminal and the EGR solenoid housing.

⇒ | If not the specified value, replace the EGR solenoid.

### 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