DTC P0401 or P0402
DTC P0401 or P0402 |
Diagnostic Instructions |
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Perform the
Diagnostic System Check - Vehicle
prior to using this diagnostic procedure.
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Review
Strategy Based Diagnosis
for an overview of the diagnostic approach.
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Diagnostic Procedure Instructions
provides an overview of each diagnostic category.
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DTC Descriptors |
DTC P0401 00
Exhaust Gas Recirculation (EGR) Flow Insufficient
DTC P0402 00
Exhaust Gas Recirculation (EGR) Flow Excessive
Circuit/System Description |
The exhaust gas recirculation (EGR) valve is controlled by the engine control module (ECM) through the EGR valve. A reference voltage is supplied to the EGR valve. The ECM controls the valve by grounding the control circuit.
Conditions for Running the DTC |
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The ignition is ON or the engine is running.
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The DTCs run continuously when the above conditions are met.
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Conditions for Setting the DTC |
P0401
The ECM detects the EGR flow is below a calibrated amount when the EGR is commanded ON.P0402
The ECM detects the EGR flow is above a calibrated amount when the EGR is commanded OFF.Action Taken When the DTC Sets |
DTCs P0401, and P0402 are Type B DTCs.
Conditions for Clearing the DTC |
DTCs P0401, and P0402 are Type B DTCs.
Reference Information |
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
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Circuit Testing
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Connector Repairs
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Testing for Intermittent Conditions and Poor Connections
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Wiring Repairs
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DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification |
1. |
Ignition ON, observe the DTC information with a scan tool. Verify that no other DTCs are set.
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2. |
If any other DTCs are set, refer to
Diagnostic Trouble Code (DTC) List - Vehicle
for further diagnosis.
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3. |
DTCs P0401 or P0402 should not set.
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4. |
Command the throttle plate from 5-95% with a scan tool. The throttle plate should respond to the scan tool commands.
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5. |
If the throttle body does not respond to the scan tool commands, refer to
DTC P2100, P2102, or P2103
for further diagnosis.
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6. |
Command the EGR Valve from 5-95% with a scan tool. The EGR valve should respond to the scan tool commands.
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7. |
If the EGR solenoid does not respond to the scan tool commands, refer to
DTC P0403, P0489, or P0490
for further diagnosis.
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8. |
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.
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Circuit/System Testing |
1. |
Ignition OFF, inspect for the following:
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Intake system/charge air hoses for leaks/restrictions
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Exhaust system/turbo charger for leaks/restrictions
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Air filter for restrictions
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2. |
Engine running at idle, command the EGR Valve to 95% with a scan tool. Verify that the mass air flow (MAF) Sensor parameter is less than 5 g/s.
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3. |
If the parameter is greater than the specified value, replace the Q14 Exhaust Gas Recirculation (EGR) Valve.
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4. |
Command the EGR Valve to 5% with a scan tool. Verify that the MAF Sensor parameter is greater than 14 g/s.
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5. |
If the parameter is less than the specified value, replace the Q14 Exhaust Gas Recirculation (EGR) Valve.
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6. |
Verify the DTC does not reset.
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7. |
If the DTC is set, replace the K20 Engine Control Module.
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Repair Instructions |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
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Exhaust Gas Recirculation Valve Replacement
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Control Module References
for Engine Control Module replacement, setup, and programming
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