GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2007 🢒 TopKick C-Series (Conventional) C6/C7/C8 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC 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 Descriptor

DTC P0402: Exhaust Gas Recirculation (EGR) Flow Excessive

Circuit/System Description

The engine control module (ECM) tests the exhaust gas recirculation (EGR) flow when the EGR is in operation. EGR desired flow is compared to EGR actual flow. If EGR flow is higher than expected DTC P0402 will set.

Conditions for Running the DTC
    • DTCs P0016, P0027, P0079, P0080, P0101, P0102, P0103, P0112, P0113, P0117, P0118, P0126, P0201, P0202, P0203, P0204, P0205, P0206, P0261, P0264, P0267, P0270, P0273, P0276, P02E7, P02E8, P0335, P0336, P0401, P0403, P0404, P0409, P042E, P0500, P0506, P0507, P0602, P0642, P0643, P0652, P1125, P1293, P2002, P2100, P2146, P2147, P2148, P2149, P2150, P2151, P2227, P2228, P2229, P2545, P268A are not set.
    • The following conditions are met for 6 seconds:
       - The engine is running.
       - The engine did not stall.
       - The vehicle speed is between 0-410 km/h (0-255 mph).
       - The barometric pressure (BARO) is between 75-120 kPa.
       - The intake air temperature (IAT) is between -7 and +120°C (+20 and +248°F).
    • The following conditions are met:
       - The battery voltage is between 10-16 volts.
       - The ignition is ON for longer than 2 seconds.
       - The accelerator pedal position is less than 101 percent.
       - The EGR control is ON.
       - The engine coolant temperature (ECT) is between 58-95°C (136-203°F).
       - The exhaust brake is OFF.
    • The following conditions are met for 5 seconds:
       - The exhaust throttle command is OFF.
       - The intake throttle position is less than 55 percent.
       - The DPF status is zero without the regeneration event.
       - The DPF differential pressure is between -10 and +20 kPa.
       - The VNT control is in normal mode.

Conditions for Setting the DTC

The actual mass air flow (MAF) value is less than the target MAF value.

Action Taken When the DTC Sets

DTC P0402 is a Type B DTC.

Conditions for Clearing the DTC

DTC P0402 is a Type B DTC.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Engine Controls Component Views
    •  Engine Control Module Connector End Views

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

Circuit/System Verification

    Important: If you cannot duplicate the condition, 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.

  1. If DTC P0101, P0403, P0405, P0406, P0698, or P0699 are set diagnose these DTCs.
  2. Using the output controls on the scan tool command the EGR solenoid to 10 percent.
    3. ⇒If the actual EGR position remains stationary, replace the EGR valve.
  3. Inspect the exhaust system for leaks, restrictions, or for modifications of the original equipment manufacture (OEM) parts.
  4. Visually inspect for leaks between the MAF sensor and the turbocharger.
  5. Visually inspect for a restriction in the air cleaner or the air intake ducts.
  6. Visually inspect for a restriction in the turbocharger charge air cooler.
  7. Visually inspect for a restriction in the intake manifold.

Circuit/System Testing

Important: Perform the Circuit/System Verification before proceeding with the Circuit/System Testing.

Inspect the charge air cooler for leaks.

⇒If no condition is found, perform the component testing.

Component Testing
  1. Using the output controls on the scan tool command the EGR position to 10 percent.
    2. ⇒If the actual EGR position remains stationary replace the EGR valve.
  2. Spray the EGR valve gaskets and EGR cooler gaskets with a soap solution. Start the engine. Command the turbocharger vane position control solenoid ON to 100 percent and inspect for leaks around the EGR valve gaskets.
    3. ⇒If a leak is found replace the EGR valve gasket.
  3. Inspect that the EGR is not stuck , that there are no leaks or restrictions in the EGR valve and EGR passages, and that there is no debris or damage that can cause the EGR valve to stick partially open or partially closed.
    4. ⇒If the EGR valve is sticking, or is damaged, replace the EGR valve.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Exhaust Gas Recirculation Valve Replacement