help p0401

[zadam123]

I got the check engine light with error code p 0401 It says it's the eger valve but I put a new 1 and and it still having a check engine with the same code. what else could it be?

I also cleaned it out with carb cleaner and still have the code

[Y33TREKker]

In my opinion, I would pay particular attention to the four sentences that begin with, "The number of test samples required to..."

How many times have you driven (keyed/started the engine, keyed/stopped the engine) your VX since replacing the EGR? This is what I meant last time when I said that a vehicles' PCM requires a certain number of inputs before it can determine what normal operating conditions currently are, (aside from the hard-coded-parameters/factory-settings that are considered normal operating ranges for each particular sensor).

Have you actually had your PCM reset to clear all old codes since replacing the EGR?

[Ldub]

Have you actually had your PCM reset to clear all old codes since replacing the EGR?

Good point Trek...:_wrench:

[zadam123]

The only way I could reset the code is by disconnecting both positive and negative terminals on the battery for 1 half hour. I drove a carl 20 miles in the code came back on

[Y33TREKker]

The only way I could reset the code is by disconnecting both positive and negative terminals on the battery for 1 half hour. I drove a carl 20 miles in the code came back on
Is there a way for determining if all past codes have been cleared when disconnecting the battery like that? I mean, I've heard it suggested many times that that's all it should take, but how does a person know if it actually worked?

How many such trips in total have you taken since replacing the EGR?

[89Vette]

Disconnecting the battery for 1/2hr will reset codes. This can be verifying by the fact the light didn't display for 20 minutes.

Pinging is caused when combustion temps get so hot that cylinders begin to fire BEFORE they're supposed to. They fire before the intake valve closes to finish inputting the gas/air mixture. With a premature explosion, the valves get SLAMMED back shut (causing a ping which is not good if done too many times.) To prevent engine damage from this phenomenon, engineers came up with the EGR system....

This EGR system typically has a tube coming from the exhaust manifold. That tube is nothing more than a pathway for exhaust to get back into your intake. And the EGR itself, is an electronic gateway for that pathway. When you "open that door" pressure changes in the manifold -- just like it changes when you open a window in a moving car.

The EGR valve valve sends (uses) a small amount of exhaust fumes to dilute/quench the intake charge. In doing so, it doesn't burn as hot and prevents detonation (pinging).

When the MAP doesn't show a pressure change (during an EGR cycle), the ECM has to assume it's malfuntioning. With this logic, I have to assume the MAP is bad, the EGR is bad, or the EGR pathway is plugged up.

Considering that the ECM (computer) checks manifold pressure during a recirculation cycle (to determine if the EGR is working), I think the next best course of action is to replace the MAP (manifold air pressure) sensor and/or EGR (exhaust gas recirculating) passageway(s).

Take this knowledge and the test chart provided by deermagnet. If you are capable, this should direct you to your problem.

Good luck!

[Ldub]

Disconnecting (readers digest condensed version) problem.

Good luck!

That might be the best, & most succinct explano I've ever seen...:yesgray:

Two of these to you Vette...:thumbup:.:thumbup:

[zadam123]

How many such trips in total have you taken since replacing the EGR?

I have taken maby 3 like trips and then cleand out the egr passage with carb cleaner then drove 20 miles befor the light came on again.

how long or how many trips should i drive the car befor this light shuts off?

also the MAP sensor , where is it? is it easy to change?

[Paul_A]

All I can say is I had 401 persistently.... no matter what I did. New egr, cleaned the pipes, new gasket... everything I could think of..... turned out to be... yep ... intake manifold gaskets. Why the 401 though?? doesn't make sense :confused::confused::confused:

[89Vette]

I bet the MAP is in the intake...and the bad intake gaskets affected pressure readings during the EGR cycle.

Another thing to consider is a wiring problem for the EGR/MAP sensor. Any intermittent connection to those sensors would cause an issue.

[Y33TREKker]

I have taken maby 3 like trips and then cleand out the egr passage with carb cleaner then drove 20 miles befor the light came on again.

how long or how many trips should i drive the car befor this light shuts off?

Short of having actual Isuzu testing equipment, all I can say is that referring back to those same four sentences I mentioned last time is all that can be done.

"The number of test samples required...may vary according to..."

"Normally, the PCM will only allow for one EGR flow test sample to be taken during an ignition cycle." (Does this "ignition cycle" mean the entire time between when the engine is started and when it's finally shut off for that first test run after getting the new part put in? Depends on a persons' interpretation of "ignition cycle".

"To aid in verifying a repair, the PCM allows twelve test samples during the first ignition cycle following a Tech 2 "Clear info" or a battery disconnect."
How often does it take to run these twelve test samples? 20 minutes perhaps? I don't know.

"Between nine and twelve samples should be sufficient for the PCM to determine adequate EGR flow and pass the EGR test."
Could it possibly have taken around 20 minutes to take the nine-twelve samples that resulted in your EGR code being generated again even after you replaced the EGR valve? I don't know. Maybe someone will chime in with more info on how often these test samples are taken as an ignition cycle is occurring.

[zadam123]

All I can say is I had 401 persistently.... no matter what I did. New egr, cleaned the pipes, new gasket... everything I could think of..... turned out to be... yep ... intake manifold gaskets. Why the 401 though?? doesn't make sense :confused::confused::confused:

how did you find out it was that?

[Amnesia]

I used to have the p401 forever & ever too... Replaced the EGR once. Fixed for a few months, then CEL came back with that code again. Lived with it for another 100k miles. Finally after replacing the intake gaskets and cleaning the heck out of the IAC, throttle body, etc. The code went away. Gone for around 25k miles now.

I had replaced the intake gaskets once before for an idle related issue, but I think that when I did it, I accidentally dinged one of the gasket surfaces while re-installing the intake. (Careful with the back right corner when re-installing...) The 2nd time I did it around 50k mile after the first time, I caught myself and realized what I had probalby done to compromise the job the first time. Since doing it the 2nd time. All has been well.

[blacksambo]

The intake gaskets are the VX engine's achilles heel. When replacing they are composed of a sandwhich type material with very brittle outer surfaces. Hand tighten down to only 13lbs torque. You can check to see if they are malfunctioning by simply spraying the outer edges of thesegaskets with carb cleaner to to see if the idle goes up while running. If the idle changes, the gasket is leaking and you will get CEL codes. (Typically, 171 and 172, if my memory serves me right.)

[zadam123]

Is this something that is easy fix. I'm not the most mechanically inclined, although changing egr was easy. can I see the intake gasket and where is it located.

[Ldub]

Is this something that is easy fix. I'm not the most mechanically inclined, although changing egr was easy. can I see the intake gasket and where is it located.

Changing the EGR is two bolts & a plug...

Changing intake gaskets is a LOT more involved...:_wrench:

I'm not trying to be harsh here, just realistic.

If you don't know where to look for the intake gaskets, the job is most likely beyond your skill set...:flower:

Not that there is anything wrong with that...:yesgray:

We all get different aptitudes & skills.

[tom4bren]

Yah, Dub's skill is being a silver tongue devil & his aptitude is bein a skull monger.:):):)

[Ldub]

Yah, Dub's skill is being a silver tongue devil & his aptitude is bein a skull monger.:):):)

Offsethammer was already taken...:rotate:

[Vendetta]

http://www.ohioriders.net/images/smilies/07302010/eatdrink.gif

[LittleBeast]

Have you tried: vacuum control solenoid (part #8-01997-201-0)?

[zadam123]

blacksambo said

"You can check to see if they are malfunctioning by simply spraying the outer edges of thesegaskets with carb cleaner to to see if the idle goes up while running. If the idle changes, the gasket is leaking and you will get CEL codes. (Typically, 171 and 172, if my memory serves me right.)"

couple of questions
I understand this may be beyond my handleing but where is it so i can try this spray test?

and will this throw these codes 171 and 172 or can i throw a p0401?

and last

littlebeast where is vacuum control solenoid ?

thanks for all the help. I have gone to 3 diffrnent mechanics and nobody has the tec 2 machine to test then and wont help me .

[VXR]

http://www.ohioriders.net/images/smilies/07302010/eatdrink.gif

:confused:

[Vendetta]

We meet again, blue-faced question marky guy. Here, let me explain. See that dude chilling out, eating popcorn and sampling his preferred beverage as he settles in to watch and enjoy the playful ribbing between his two friends Tom4 and Dub? That's me.

[VXR]

We meet again, blue-faced question marky guy.

:laughb: