Rodeo02 - Lesson learned, help w/ P0401

Wasn't happy with what the guy said at Autozone yesterday, so I went back today.

I've learned my lesson not to jump too soon, and I doubt I can return the O2 sensors, but not much I can do now but keep them. And install them as I need them.

The code read from the CEL was P0401 - insufficient flow

Common on the 98+, from my search, but not common on the 97's. However, is cleaning the EGR pretty much the same, AND can I do this with the truck off?

What causes this?

And obviously I imagine it's ok to drive till Saturday?? As I'm sure every Rodeo has EGR problems every day of the week.

P0401 = Exhaust Gas Recirculation Flow Insufficient Detected. Your EGR valve is not working right, the transducer that regulates the vacuum to the dome of the EGR valve is not working properly, the sensor that measures EGR flow is caput, or the EGR plumbing is clogged (common on 1998+) I am not familiar with the EGR systems on the 1993-1997 as they are completely different than the 1998+ You don't hear of too many EGR issues with 1993-1997. Hopefully others will chime in!

G/luck
Joel

Figures - something that I could have possibly done has got to go and be so damned technical.

I just hope it's not one "trouble code" that leads into another.

Well, for now, I'm just gonna throw some Techron in and see where that gets me.

I believe I can return those O2 sensors with a re-stocking fee, that'll give me some money back to just take it into my mechanic.

See, I knew it wasn't going to be as simple as just changing out the O2 sensors.

P0401.
ECM perform test like drop rpm from about 3500 to idle and looking for
specific value response from MAP sensor, if not code is set. Chart said look for other codes like P0406 and resolve these first. Than check MAP sensor,perform test, if response no good replace MAP sensor(my idea may be clean MAP sensor first).Not sure how monitor MAP sensor without
Tech 2 tool.If MAP OK, than EGR turn.Clean everything as of Amigo-2k FAQ.

I cleaned the EGR valve on my 95.5 rodeo about a year ago, and it was ridiculously easy. Probably didn't take me more than 15 minutes and that was taking my time.

Worth a try before bringing it to the mechanic. Get some carb cleaner or seafoam deep creep and spray the heck out of the EGR valve. To remove the EGR, you just pull off the rubber vacuum hose, disconnect the metal exhaust tube going to the EGR by loosening the nut, then remove the two mounting bolts that hold the EGR valve in place. Once it's off just spray the living daylight out of it while working the plunger in and out. You can probably reuse the EGR gasket if you're careful when taking the valve off, though it is a pretty tough gasket so you should be fine.

So, it is basically the same cleaning procedure as for the 98+?

I've read that it's RARE for one to actually go bad - so yes, I'm definitely willing to clean it first.

I found where it's located at, is the removal of it the same?

How do I clean the MAP sensor as well?

P0401.
ECM perform test like drop rpm from about 3500 to idle and looking for
specific value response from MAP sensor..

Good point. On the 1993-1997 3.2 rodeos, the ECM must trigger the EGR vlv to open & then attemps to measure the change in pressure from the manifold air pressure sensor (MAP) indicating that the EGR is functioning or not. Some cars have a seperate dP sensor for the EGR, some use the MAP. The 1998+ uses the EGR vlv itself to 'measure' flow (called a feedback EGR).

Joel

Well the MAP sensor is out of my hands, don't have any special tools.

Here's the plan, I'm gonna clean the EGR, replace the two O2 sensors off the manifolds, and see where that gets me. An Isuzu tech stated that a "going bad" O2 sensor "can" trigger a faulty EGR reading - and I already have them, so it can't hurt.

I am going to send back the two O2 sensors from the rear - and recoup a little bit of $$$.

Chances are it's something other then the two items I'll be working on - but I can't take the truck to my mechanic for at least 2-3 weeks.

So I can only hope that it doesn't get worse.

Truck's running fine - just getting a little fuel smell at start-up.

That sounds like a good plan of action. EGR cleaning and upstream O2 sensor(s) replacement. I'm not sure how the <1998 EGR system is jetted in the plenum, but @ 150Kmi, it is probably very dirty and/or clogged. At that mileage, it's also possible you will see increased engine performance from new upstream O2 sensors as well. The old ones *could* have slowed down a bit in reaction time, but not enough to set off a CEL.
G/luck
Joel

Finally got a hold of my mechanic, just wanted his opinion. He highly doubts that it has anything to do with the O2's or the EGR - as the truck is running completely normal.

In his opinion, the autozone guys only give people basic generic codes, and they're generally more confusing then helpful - granted this is his opinion, I have no opinion on Autozone right now because I don't know what it is.

But I do know that I've known this mechanic a LONG time, and he's been right on with every import vehicle we've owned - so I'm gonna take his advise and send all the O2's back.

He says not to worry, as it's a steady CEL light, not flashing, and just drive the thing until I have the $$$ and time to take it in. Says it won't effect anything.

Hope not. Anyway, thanks for all the help - if there are any symptoms that arise I'll post back.

Ramblin,
Regarding the p0401, Rodeo02 is right on the money. Cleaning the EGR valve should be your primary, as far as the O2 sensors, don't even bother, send them back. I went to the dealership with my 401 and the following occured: replaced EGR valve/gasket, cleaned the gunk out of the vacuum port and TB, than a full fuel injection cleaning for the low price of $495.00 (that also included state inspection and 2 hours of labor at $92/hr). Depending on where you live, if you have to get an emissions test done with the 401...you will fail, plus you will start to notice lower fuel economy. Hope this helps.
KC

By the way you can delete this code by removing battery negative cable and pull fuse #13 (ECM) ECM backup fuse in underhood fusebox and see if code return back.

I lucked out, thank goodness, just DID emissions a month ago. It's good for 2 yrs.

Finally got a hold of my mechanic, just wanted his opinion. He highly doubts that it has anything to do with the O2's or the EGR - as the truck is running completely normal.

In his opinion, the autozone guys only give people basic generic codes, and they're generally more confusing then helpful - granted this is his opinion, I have no opinion on Autozone right now because I don't know what it is.

But I do know that I've known this mechanic a LONG time, and he's been right on with every import vehicle we've owned - so I'm gonna take his advise and send all the O2's back.

He says not to worry, as it's a steady CEL light, not flashing, and just drive the thing until I have the $$$ and time to take it in. Says it won't effect anything.

Hope not. Anyway, thanks for all the help - if there are any symptoms that arise I'll post back.


(1) Get a new mechanic.

(2) Clean the EGR as the others have suggested.

(1) Get a new mechanic.

(2) Clean the EGR as the others have suggested.

Cleaned the EGR, it really wasn't bad, but the difference in throttle response is sure there, and the CEL went away - drove for 100 miles, has not returned.

Hopefully it won't.

"Get a new mechanic" :cwm27: Not likely. Have known this guy a LONG time, and he's very trust worthy.

Try living in Las Vegas, NV for a few years, you'll get wind of some REAL bad mechanics and people that'll rob you blind.