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DTC P0400-P0402 - FX3

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 P0401: Exhaust Gas Recirculation (EGR) Flow Insufficient

DTC P0402: Exhaust Gas Recirculation (EGR) Flow Excessive

Circuit/System 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

P0401

    • DTC P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0351, P0352, P0402, P0404, P0405, P0406, P042E, P0502, P0506, P0507, or P2110 is not set.
    • The intake air temperature is between -3 and 120°C (26.6 and 248°F).
    • The vehicle speed is greater than 15 km/h (9.3 mph).
    • The throttle position is less than 1%.
    • The barometric pressure is greater than 72 kPa (10.4 psi).
    • The engine speed is between 1400-3000 RPM.
    • The EGR position is less than 1%.
    • The MAP is between 10-55 kPa (1.5-8.0 psi).
    • The change in MAP is less than 1 kPa (0.15 psi).
    • The A/C clutch state is not changing.
    • The TCC state is not changing.
    • The change in idle airflow is less than 15 g/s.
    • The DTC runs once per key cycle when the above conditions are met.

P0402

    • The engine is cranking.
    • The ignition voltage is between 10-16V.
    • The DTC runs when the above conditions are met for 3 s.

Conditions for Setting the DTC

P0401

The ECM detects that the change in MAP is greater than the predetermined values.

P0402 (LMT)

The ECM detects that the EGR position is greater than 70%.

P0402 (LMU)

The ECM detects that the EGR position is greater than 35%.

Action Taken When the DTC Sets
    • DTC P0401 is a Type C DTC.
    • DTC P0402 is a Type E DTC.

Conditions for Clearing the DTC
    • DTC P0401 is a Type C DTC.
    • DTC P0402 is a Type E DTC.

Reference Information

Schematic Reference

Engine Controls Schematics : Siemens ECM - LPG with LCP → Siemens ECM - Gas without FX3 or LCP → Delphi ECM - FX3

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, verify that the DTCs P0107, P0108, P0403, P0404, P0405, or P0406 is not set.
    2. ⇒If any DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.
  2. Verify that the DTCs P0401 or P0402 is not set.
  3. Ignition ON, verify that the scan tool EGR Position Sensor parameter is between 0-4%.
  4. 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:
    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 build-up 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

       Note: 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 chain installation--Refer to Symptoms - Engine Mechanical.
  2. If all conditions 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

   


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