Fix code P0400 Nissan Altima EGR Malfunction
Nissan’s P0400 Nissan Altima EGR Malfunction is similar to other manufacturers. The PCM pulses a solenoid to regulate how much vacuum the EGR valve gets. That determines how far the valve opens. To determine if the valve is actually opening, the PCM looks to the EGR backpressure transducer and the EGR temperature sensor.
If you get the P0400 Exhaust Gas Recirculation Flow Malfunction code, first check to make sure the hose to the bottom of the EGR valve is intact and not burned. If that checks out, “T” a vacuum gauge into the line to the EGR valve and drive the vehicle. If you see vacuum, that will confirm that the PCM is commanding it and that the solenoid is providing it. The vacuum gauge should read between 2”-4” of vacuum. If you don’t see vacuum, check the hoses and the solenoid for malfunction.
Next, connect a voltmeter to the blue/yellow wire on the temperature sensor. With the engine running, apply vacuum and watch the voltage reading. The engine should run rough at idle and the reading should drop to less than 1 volt very quickly. If you don’t see that drop and you’ve already confirmed that the EGR is operating properly, replace the temperature sensor.
© 2012 Rick MuscoplatPosted on by Rick Muscoplat