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 P0400: Exhaust Gas Recirculation (EGR) Flow Incorrect
DTC P0402: Exhaust Gas Recirculation (EGR) Flow Excessive
DTC P1402: Exhaust Gas Recirculation (EGR) Flow Insufficient

### Circuit Description

The engine control module (ECM) performs a flow test on the exhaust gas recirculation (EGR) system during deceleration. The ECM does this by momentarily commanding the EGR valve to open while monitoring the signal of the manifold absolute pressure (MAP) sensor and the EGR position sensor. If the MAP signal is incorrect for the EGR pintle position, the ECM records the amount of MAP difference that was detected and adjusts a calibrated fail counter towards a calibrated fail threshold level. The number of EGR flow tests required to exceed the fail threshold may vary according to the amount of detected EGR flow error.

Normally, the ECM will only allow one EGR flow test during an ignition cycle. To aid in verifying a repair, the ECM will allow multiple EGR flow tests following a code clear event.

### Conditions for Running the DTC

• | DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0131, P0300, P0335, P0336, P0341, and P0342 are not set.

• | The EGR flow test is ran in decel fuel cut-off (DFCO) mode with the following conditions present before deceleration occurs:

- | The engine is operating in closed loop.

- | The ignition 1 voltage is between 11-16 volts.

- | The A/C compressor clutch does not change state during deceleration.

- | The intake air temperature (IAT) sensor is more than 15°C (59°F).

- | The engine coolant temperature is more than 60°C (140°F).

- | The manifold absolute pressure (MAP) is more than 75 kPa.

- | The engine airflow is between 71-174 mg/tdc.

- | The engine speed is between 1,950-2,600 RPM.

- | The EGR is more than 10 percent.

• | The DTCs runs once per ignition cycle once the above conditions are met.

### Conditions for Setting the DTC

#### P0400

The MAP changes monitored by the ECM during the EGR flow tests indicate an incorrect amount of EGR flow.

#### P0402

The MAP changes monitored by the ECM during the EGR flow tests indicate an excessive amount of EGR flow.

#### P1402

The MAP changes monitored by the ECM during the EGR flow tests indicate an insufficient amount of EGR flow.

### Action Taken When the DTC Sets

DTCs P0400, P0402, and P1402 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P0400, P0402, and P1402 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. Engine running, observe the DTC information with a scan tool. DTCs P0107, P0108, P0404, P0405, P0406, P1403, or P1404 should not set.

⇒ | If any DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.

2. Observe the DTC information with a scan tool. DTCs P0400, P0402, or P1402 should not set.
3. 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. Verify one of the following conditions is not present:

• | Incorrect EGR valve for engine application.

• | A vacuum leak between the EGR valve and the intake manifold.

• | Signs of external leakage usually indicated by carbon buildup around the mating surfaces of the components or an audible exhaust noise.

• | Restrictions in the passages or EGR valve caused by carbon deposits or casting flash.

• | Restrictions in EGR pipe caused by carbon deposits or casting flash.

• | Leaks or restrictions at the manifold absolute pressure (MAP) sensor.

| Important: Restrictions can cause excessive back pressure and low engine vacuum.

• | Leaking, restricted, or modified exhaust system--Refer to Symptoms - Engine Exhaust.

• | Mechanical failure in the engine such as worn piston rings, camshaft or incorrect timing belt installation--Refer to Symptoms - Engine Mechanical.

2. If all conditions test normal, test or replace the EGR valve.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Exhaust Gas Recirculation Valve Replacement