DTC P0400-P0402 - LNP or LNQ
Diagnostic Instructions
DTC Descriptors
DTC P0400 00: Exhaust Gas Recirculation (EGR) Current Performance
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
• | The ignition is ON or the engine is running. |
• | The DTCs run continuously when the above conditions are met. |
Conditions for Setting the DTC
P0400 00
The ECM detects the EGR flow is out of the calibrated range.
P0401 00
The ECM detects the EGR flow is below a calibrated amount when the EGR is commanded ON.
P0402 00
The ECM detects the EGR flow is above a calibrated amount when the EGR is commanded OFF.
Action Taken When the DTC Sets
DTCs P0400 00, P0401 00, and P0402 00 are Type B DTCs.
Conditions for Clearing the DTC
DTCs P0400 00, P0401 00, and P0402 00 are Type B DTCs.
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Ignition ON, observe the DTC information with a scan tool. Verify that no other DTCs are set.
- DTCs P0400 00, P0401 00 or P0402 00 should not be set.
- Command the throttle plate from 5-95% with a scan tool. The throttle plate should respond to the scan tool commands.
⇒ | If the throttle body does not respond to the scan tool commands, refer to
DTC P02E0-P02E3, P02E8, P02E9, P02EB, or P122B : LNP or LNQ for further diagnosis. |
- Command the EGR Valve from 0-100% with a scan tool. The EGR valve should respond to the scan tool commands.
⇒ | If the EGR solenoid does not respond to the scan tool commands, refer to
DTC P0404-P0406 : LNP or LNQ for further diagnosis. |
- 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
- Ignition OFF, inspect for the following:
• | Inlet system/charge air hoses for leaks/restrictions |
• | Exhaust system/turbo charger for leaks/restrictions |
• | Air filter for restrictions |
- Engine running at idle, command the EGR Valve to 95% with a scan tool. Verify that the MAF Sensor parameter is less than 5 g/s.
⇒ | If the parameter is greater than the specified value, replace the Q14 Exhaust Gas Recirculation Valve. |
- Command the EGR Valve to 5% with a scan tool. Verify that the MAF Sensor parameter is greater than 14 g/s.
⇒ | If the parameter is less than the specified value, replace the Q14 Exhaust Gas Recirculation Valve. |
- Verify the DTC does not reset.
⇒ | If the DTC is set, replace the K20 Engine Control Module. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
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