P0400 DTC

P0400

Technical Definition:

Exhaust Gas Recirculation (EGR) Flow

Trouble Code: P0400
Address: 0x0400
System: Powertrain
Subsystem: Auxiliary Emission Controls
Technical Description:

The exhaust gas recirculation (EGR) valve is vacuum controlled valve that regulates the amount of exhaust gases that re-enter the cylinders.

Possible Causes:
  • Plugged EGR passage which restricts the flow of exhaust gasses
  • Faulty EGR solenoid
  • Faulty EGR solenoid wiring/harness
  • Vacuum lines damaged/disconnected to the EGR valve solenoid or to the EGR valve
  • Faulty EGR valve

Possible Symptoms:

Exhaust Gas Recirculation Flow Malfunction

Possible Solutions:
  • Using a scan tool, operate the EGR valve with the engine running. If the engine stumbles, the problem was likely intermittent wiring problem or intermittent blockage problem
  • If engine doesn’t stumble, operate the EGR valve manually, if possible. If engine doesn’t stumble and die, the ports are likely plugged. Removal of valve and cleaning of all ports will be required
  • Checking of solenoid can only usually be done with a scan tool, because most solenoids operate with a duty cycle of voltage, rather than constant voltage
  • Check all vacuum lines, hoses, etc for any damage
  • Visually inspect the solenoid harness and the solenoid for damage
  • Replace EGR valve

OBD-II Trouble Code Type:

Diagnostic Step:

Tech Notes:

– Exhaust Gas Recirculation (EGR) volume control valve stuck closed
– Faulty Exhaust Gas Recirculation (EGR) volume control solenoid valve
– Faulty EGR Valve
– Faulty EGR temperature sensor and circuit
– Exhaust Gas Recirculation (EGR) solenoid valve harness is open or shorted
– Exhaust Gas Recirculation (EGR) solenoid valve circuit poor electrical connection
– Dead (Weak) battery

Specific Makes:

– Possible engine hesitation