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 Descriptor

DTC P0405 00: Exhaust Gas Recirculation (EGR) Position Sensor Circuit Low Voltage
DTC P0406 00: Exhaust Gas Recirculation (EGR) Position Sensor Circuit High Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
5-Volt Reference | P0405 00 | P0405 00 | P0406 00 | --
Signal | P0405 00 | P0405 00 | P0406 00 | --
Low Reference | -- | P0406 00 | -- | --

### Typical Scan Tool Data

#### EGR Position Sensor

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: engine running Parameter Normal Range: 0.98-4.98 V
5-Volt Reference | 0 V | 0 V | 4.98 V
Signal | 0 V | 0 V | 4.98 V
Low Reference | -- | 4.8 V | --

### Circuit/System Description

The engine control module (ECM) uses the exhaust gas recirculation (EGR) position sensor to determine the position of the EGR valve. The ECM sends a reference voltage through the 5-volt reference circuit to the EGR position sensor. The ECM provides a voltage return path for the sensor through the low reference circuit. A variable voltage signal, based on the EGR valve position, is sent from the sensor to the ECM through the EGR position sensor signal circuit. If the ECM detects an EGR position sensor voltage that is less than or more than the normal operating range, DTC P0405 or P0406 sets.

### Conditions for Running the DTC

• | The ignition is ON.

• | This DTC runs continuously when the above conditions are met.

### Conditions for Setting the DTC

#### P0405

The EGR position sensor voltage is less than 0.26 V for more than 1 s.

#### P0406

The EGR position sensor voltage is more than 4.75 V for more than 3 s.

### Action Taken When the DTC Sets

DTCs P0405 and P0406 are Type B DTCs.

### Conditions for Clearing the DTC

DTCs 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 0.25-4.75 V.
2. Operate the vehicle within the Conditions for Running the DTC. 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 Q14 Exhaust Gas Recirculation (EGR) Valve.
2. Ignition OFF, test for less than 5 Ω between the low reference circuit terminal 3 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 K20 Engine Control Module (ECM).

3. Ignition ON, test for 4.8-5.2 V between the 5-volt reference circuit terminal 1 and ground.

⇒ | If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module (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 K20 Engine Control Module (ECM).

4. Verify the scan tool EGR Position Sensor parameter is less than 0.3 V.

⇒ | If greater than the specified range, test the signal circuit terminal 5 for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

5. Install a 3 A fused jumper wire between the signal circuit terminal 5 and the 5-volt reference circuit terminal 1. Verify the scan tool EGR Position Sensor parameter is greater than 4.8 V.

⇒ | If less than the specified range, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

6. If all circuits test normal, test or replace the Q14 Exhaust Gas Recirculation (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