Oh joy, P0401 is back... (and how 80's fail emissions)

[nakman]

So on Wednesday night driving home my CEL came on. Pulled the code last night and yup, PO401. so I cleared it, driving the 80 again today and it hasn't come back on yet.

I have 2 theories: one is I am pretty sure I've got an exhaust leak, maybe multiple. Occasionally when I start the truck I can hear something rattle.. I can also get it to rattle at various RPM's, like power breaking while wheeling I can get it to rattle pretty good... second theory is the second guessing of the Landtank MAF mod... which has been in place for about 10,000 miles now.

I can't remember what all got replaced when I had 401 last time, I think the IAC valve? Maybe remembers... anyway I'm not going to do anything until the light comes on again, but am open to any peanut gallery comments in the interim. opcorn:

 

[Uncle Ben]

So on Wednesday night driving home my CEL came on. Pulled the code last night and yup, PO401. so I cleared it, driving the 80 again today and it hasn't come back on yet.

I have 2 theories: one is I am pretty sure I've got an exhaust leak, maybe multiple. Occasionally when I start the truck I can hear something rattle.. I can also get it to rattle at various RPM's, like power breaking while wheeling I can get it to rattle pretty good... second theory is the second guessing of the Landtank MAF mod... which has been in place for about 10,000 miles now.

I can't remember what all got replaced when I had 401 last time, I think the IAC valve? Maybe remembers... anyway I'm not going to do anything until the light comes on again, but am open to any peanut gallery comments in the interim. opcorn:

The leak is most likely the crotch of the Y pipe. The valve Robbie replaced is the EGR vacuum control solenoid. I have not popped a 401 since I replaced mine and I too am running Ricks MAS (happily) You might check the EGR sensor for crud build up.

 

[nakman]

Is the EGR sensor that 14mm nut deal on the top of the intake manifold? the one that was a real bugger to break free?

 

[Uncle Ben]

Is the EGR sensor that 14mm nut deal on the top of the intake manifold? the one that was a real bugger to break free?

Yup.....thats the one.

 

[ttubb]

P401

On my 80 I occasionally got the code on Scan Gage. It seemed to happen after I had been driving a while and stopped for a short time then restarted the engine. After a few minutes of highway driving I would get the code. I would reset it and the problem would not reappear for some time, like months. So I did not worry about it and it did not seem to be a problem. T

 

[Romer]

An 02 sensor would pop another code on its own, but could it contribute to the P0401?

Ialso am still running Rick's MAF with the vacuum line hooked up

 

[Corbet]

Mine disappeared this summer after being on for 18 months?

 

[powderpig]

Your solieniod was fried (no current could pass through it to pull the valve shut).
That is what I replaced last time for you. If the code comes on again. I can give you suggestions or I can come look at it and see if my work mess up.
Let me know.

 

[bigbluefj]

Code's what are these thing's you all are talkng about, NEW 80 OWNER hehe..

 

[nakman]

Ok so I cleaned up the EGR sensor thing, I guess it looked dirty but it didn't look that bad. Anyway, still no return of the code, though last time it only would happen on longer trips.


Kevin you'll know soon enough, eh.

 

[Uncle Ben]

Code's what are these thing's you all are talkng about, NEW 80 OWNER hehe..

Got Scan Tool?

 

[nakman]

bugga. CEL came on again tonight, maybe it knew I was driving back to work or something.... but it came on only a mile from home.

In addition to the 401 the scan tool says "EGR Flow Insufficient." Is that meaningful to anyone?

 

[Romer]

It means the flow on your EGR is insufficient

 

[edog 80]

I had the same on mine. It's a very intermittent code it seems. It was VSV for EGR on mine, kind of a bugger to get at. Mine would only come on going down I-25 after about an hour. Driving around town it never came on. I guess they go bad when they get hot on these older trucks. I pulled my upper intake to get at mine, but there are ways more competent mechanics than I can do without taking the intake off.

 

[nakman]

It means the flow on your EGR is insufficient

You're obviously in management. :flipoff2:

I had the same on mine. It's a very intermittent code it seems. It was VSV for EGR on mine, kind of a bugger to get at. Mine would only come on going down I-25 after about an hour. Driving around town it never came on. I guess they go bad when they get hot on these older trucks. I pulled my upper intake to get at mine, but there are ways more competent mechanics than I can do without taking the intake off.

Yeah I may wind up just having a competent mechanic come over, would probably save me money. Last time I went through the diagnostics in the FSM my head was spinning about 4 steps in...

 

[Uncle Ben]

You jinxed me Nakster! Didn't pop a 401 but I popped a 171 tonight about 20 miles prior to losing the speedo. Most likely the speed sensor as it bounces randomly all over the gauge when it wakes up briefly. (for upper management that would be Bank 1 too lean)

 

[bigbluefj]

So with all these codes coming up what should a guy look for in a scanner??

 

[Uncle Ben]

So with all these codes coming up what should a guy look for in a scanner??

Batteries! Seriously, you want to invest in the best scanner you can afford. You can at least get buy with the el cheapos as they will tell you the code and reset it for you but to go real time or data log you need to blow some cash. Of course you have already invested in a FSM and ESM just because your a smart guy and thats what smart guys buy right after they get the title.

 

[bigbluefj]

 

[Romer]

I have the autoxray4000 that reads codes and allows you to monitor as you drive. I am pretty happy with it

You should also get a factory service manual (FSM) and wiring diagram for your truck. That well help quite a bit. I am not talking the Haynes or Chilton books