DTC P0400, P0401, P0402, or P1402. Chevrolet Joy 2008

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

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Ignition 1 Voltage | P0342, P0562 | -- | -- | P0400, P0402, P1402
Solenoid Control | P0403 | -- | P0403, P0563 | P0400, P0402, P1402
5-Volt Reference | P0107, P0404, P0405 | P0404, P0405 | -- | P0400, P0402, P1402
EGR Position Sensor Signal | P0403, P0405 | P0404, P0406 | P0404, P0406 | P0400, P0402, P1402
Low Reference | -- | P0404, P0406 | -- | P0400, P0402, P1402

### 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. If the ECM detects an EGR flow error, this DTC sets.

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 P0403, P0404, P0405, and P0406 are not set.

• | The engine is running.

• | The engine speed is between 2,368-3,200 RPM.

• | The calculated air flow is between 87.15-168.86 mg/tdc.

• | The engine coolant temperature is greater than 70°C (159°F).

• | DTC P0400, P0402, and P1402 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

#### 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. Verify that DTC P0107, P0108, P0403, P0404, P0405, or P0406 is not set.

⇒ | If any DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle.

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 none of the following conditions exist.

• | 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

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

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

• | Leaks or restrictions at the MAP sensor

• | 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, replace the EGR valve.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Exhaust Gas Recirculation Valve Replacement