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 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

• | 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. With a scan tool, command the EGR solenoid ON. You should hear an audible click for about 3-5 seconds.
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 Data List.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector of the EGR solenoid.

Important: The test lamp is used to load the circuit and may not illuminate.

2. Connect a test lamp between the ignition 1 voltage circuit of the EGR solenoid and ground.
3. Command the fuel pump relay ON with a scan tool and load test for battery voltage between the ignition 1 voltage circuit of the EGR solenoid and ground.

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

4. With the ignition OFF, connect a test lamp between the control circuit and the ignition 1 voltage circuit of the EGR solenoid.
5. With the ignition ON, use a scan tool to command the EGR solenoid ON and OFF. The test lamp should turn ON and OFF.

⇒ | If the test lamp remains ON all the time, test for a short to ground on the control circuit. If circuit/connections test normal, replace the ECM.

⇒ | If the test lamp remains OFF all the time, test for a short to voltage or an open/high resistance on the control circuit. If circuit/connections test normal, replace the ECM.

6. If all circuits/connections test normal, test or replace the EGR solenoid.

### Component Testing

1. Measure for 24-28 ohms of resistance between the terminals of the EGR solenoid.

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

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

⇒ | If less than infinite resistance, 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