» » »

Toyota Q&A

Ask Your Question

1999 Toyota Camry Question: what to P0401 and P0402 mean ?? I just replaced my egr vacuum modulator as well.

 

Question

jstov77, 2.2L 4 Cylinder, Bedford, TX, January 01, 2012, 18:31
 Rookie

changed the modulator today and now have both trouble codes... what should I do , I do not have a rough idle or it does not die ..... dont know what to do

1 Answer
Flag This
  • Answer #1

    January 02, 2012, 03:05
    Profile_thumbnail
     Master

    Customer Concern: The check engine light is on with a trouble code P0401.

    Tests/Procedures: 1. Verify that the vehicle will stall at idle when the Exhaust Gas Recirculation (EGR) valve is opened.

    2. Monitor the vacuum signal to the EGR valve, while driving the vehicle, and it should be 3 to 7 inches. If the vacuum is low, verify that the ports are clean and the intake and EGR vacuum modulator operate correctly.

    3. Next, verify that the EGR Vacuum Switching Valve (VSV) under the intake is not causing the low vacuum signal to the EGR valve. Also, verify that the EGR VSV is turning on and off by the Engine Control Module (ECM) when driving the vehicle and when the engine is cold. When everything checks OK, the EGR VSV is the common failure. It can test just fine and cause the code to set.

    4. Check and clean the filter located in the intake manifold that supplies the vacuum signal to the Manifold Absolute Pressure (MAP) sensor.

    5. Verify that the O2 sensor functions correctly and does not cause any type of surge when driving.
    Tech Tips: The EGR VSV is located on the bottom of the intake manifold.

    Customer Concern: The check engine light is on with an EGR System Insufficient Flow code P0401 and an Excessive EGR Flow code P0402.

    Tests/Procedures: 1. If the engine is running rough, check if the EGR valve is partially stuck open mechanically.

    2. Verify that the vehicle will stall at idle when the Exhaust Gas Recirculation (EGR) valve is opened.

    3. Monitor the vacuum signal to the EGR valve, while driving the vehicle, and it should be 3 to 7 inches. If the vacuum is low, verify that the ports are clean and the intake and EGR vacuum modulator operate correctly. Verify that the vacuum bleeds off when the throttle is closed.

    4. Verify that the EGR Vacuum Switching Valve (VSV) under the intake is not causing the low vacuum signal to the EGR valve or not bleeding off the vacuum to close the EGR valve. Also, verify that the EGR VSV is turning on and off by the Engine Control Module (ECM) when driving the vehicle and when the engine is cold. When everything checks OK, the EGR VSV is the common failure. It can test just fine and cause the code to set.

    5. Check if the vacuum lines are swapped at the EGR Vacuum Switching Valve (VSV).

    Reply
    Flag This