GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2007 🢒 Epica 🢒 Engine 🢒 Engine Controls and Fuel - 2.0L and 2.5L 🢒 DTC P0400, P0401, or P0402

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 P0400:  Exhaust Gas Recirculation (EGR) Flow Incorrect

DTC P0401: Exhaust Gas Recirculation (EGR) Flow Insufficient

DTC P0402: Exhaust Gas Recirculation (EGR) Flow Excessive

Circuit Description

The engine control module (ECM) performs a insufficient flow test on the exhaust gas recirculation (EGR) system during deceleration and an excessive flow test during engine crank.

The insufficient flow test is when the ECM 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. The ECM will only allow one EGR flow test during an ignition cycle. Following a code clear event, the ECM will perform multiple EGR flow tests.

The excessive flow test is when the ECM monitors the position of the EGR valve during engine crank. The EGR valve should not be open during engine crank.

Conditions for Running the DTC
    • DTCs P0403, P0404, P0405, and P0406 are not set.
    • The engine speed is between 1,888-2,496 RPM.
    • The ignition 1 voltage is between 10-16 volts
    • The manifold absolute pressure (MAP) is greater than 150 hPa.
    • The engine coolant temperature (ECT) is greater than 70°C (159°F).
    • The intake air temperature (IAT) is greater than 9°C (48°F).
    • The throttle position (TP) is between 2.341-13.122 degrees.
    • The DTCs run continuously 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 for up to 6 seconds.

P0401

The MAP changes monitored by the ECM during the EGR flow tests indicate an insufficient amount of EGR flow for up to 6 seconds.

P0402

The ECM detects excessive EGR flow due to the EGR valve pintle being open more than 57 percent during crank for up to 6 seconds.

Action Taken When the DTC Sets

DTC P0400, P0401 and P0402 are Type A DTCs.

Conditions for Clearing the MIL/DTC

DTC P0400, P0401 and P0402 are Type A 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. Verify that DTCs P0107, P0108, P0403, P0404, P0405, and P0406 are not set.
    2. ⇒If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
  2. Ignition ON, observe the EGR Position Sensor parameter. The reading should be between 0-4 percent.
  3. 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. DTCs P0400, P0401 or P0402 should not set.
  4. 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 List.

Circuit/System Testing
  1. Verify none of the following conditions exist:
    2. • 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
    • Leaks or restrictions at the 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. Ignition OFF, disconnect the harness connector of the EGR valve.
  3. Ignition OFF, verify a test lamp does not illuminate between the control circuit and B+.
    4. ⇒If test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.
  4. If all circuits test normal, replace the EGR valve.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Exhaust Gas Recirculation Valve Replacement
    •  Exhaust Gas Recirculation Valve Pipe Replacement
    •  Control Module References for ECM replacement, setup, and programming