[Jthomas590]

Got the p0401 code and the car stutters when stopped and the lights flicker.
I have checked:
Intake manifold cleaned and cleared egr ports
Check vacuum lines
Egr valve has been cleaned and check with vacuum pump for valve function and also while the car is running which stalls when vacuum is applied
VSV checked at 12v and air only flows when applied
Egr modulator has air flow through and clean filter on top, bottom holds a vacuum
Plug to VSV is metering at 0v at idle and up to 13v when open throttle
MAP sensor holds vacuum, one wire in plug is at 5v and another at 3.6v and drops 1v when 5in/hg vacuum is applied.

Any other suggestions? Could it be a bad ECU? Any help would be great thank you.

 

[DannoXYZ]

The ECU detects insufficient EGR flow based upon either exhaust-temp sensor or MAP-sensor values.

1. does your car have exhaust-temp sensor?
2. what is vacuum at idle?
3. what is MAP-sensor voltage at idle vacuum?

 

[Jthomas590]

1. Ill have to check to see if it does
2. Where should I check and what should it be at?
3. At idle it was reading 3.6 volts

 

[Jthomas590]

Bump

 

[Jthomas590]

Bump

 

[Pete Suhman]

2. Where should I check and what should it be at?

Probably anywhere on the intake manifold. Disconnect a hose and hook up the gauge to the engine-vacuum side of the connection. Not sure what idle vacuum should be, but it's probably pretty high, like over 20 lbs. Do you have a vacuum gauge?

 

[Jthomas590]

Yes i do. I was going to replace all the vacuum lines maybe tomorrow and ill check that. What would be the next step if it is low?

 

[Chris94]

This video seems to give a good explanation of how to use a vacuum gauge, and what different symptoms could show up as.

 

[DannoXYZ]

The ECU detects insufficient EGR flow based upon either exhaust-temp sensor or MAP-sensor values.

1. does your car have exhaust-temp sensor?
2. what is vacuum at idle?
3. what is MAP-sensor voltage at idle vacuum?

1. Ill have to check to see if it does
2. Where should I check and what should it be at?
3. At idle it was reading 3.6 volts

1. does your car have exhaust-temp sensor?
2. what is vacuum at idle? Test it by using rubber-T at the FPR or MAP-sensor
3. IF your MAP-sensor is putting out 3.6v @ idle and 1.0v @ 5-in.Hg you've got some problems. Measure the following:

______MAP____VACUUM
key ON= ?volts__?-in.Hg
idle = ?volts____?-in.Hg

We have to determine the current configuration (yes/no EGR temp-sensor), and its current condition (MAP/Vacuum, etc.) in order to compare to ideal optimum working-conditions. Any deviation in measurements will give us an idea of where to look at for resolution. Without the data in numeric form, you might as well start replacing everything in the engine-compartment with known-good and tested parts. At some point, the problem will be fixed.