CEL, P0401 Code, how bad is it?

[Shahram]

Yes, I searched, and yes, it was really helpful...

The one thing I'd like to know is, is it really bad for me to be driving around with insufficient exhaust recirculation? It's just that I'm really busy right now, I've got crazy amounts of work, have to do a bit of driving, and can't work on it until next week. Seems to me the less exhaust going back into the engine the better, but my thinking could be slightly flawed...I am getting a bit of a "ping" when I throttle, so that may be it...

What do you think? Thanks for any and all advice, admonishment and derision in advance.

 

[ParadiseCruiser]

S -

According to Toyota's official recommendation, you should not drive around with a P0401.

Numerous members of this list have done so anyway... and some as long as six months with no ill effects. Personally, I drove around for several weeks before I chased after the problem on mine. YMMV.

As long as there are no real obvious problems, I would think that a week shouldn't matter much, but if you're pinging, fix it (petrol, timing, fuel, whatever...). Whether it is related or not, that's not a good thing.

Cheers, R -

 

[Shahram]

Cool, thanks.

 

[turbocruiser]

There are several answers to this just as there are several problems that cause the PO401 ... If for example the diaphram (sp?) to the modulator blows to bits then driving around with the PO401 really means that you are cramming up your VSV with carbon and crap. If the VSV is out, then driving around might mean you are allowing too much carbon and crap to accumulate elsewhere. It is all interconnected. For a while there were several who stated that the EGR system can raise the temps to the engine if the system is malfunctioning and while this is true technically, I'm not sure it matters much; by definition when the EGR system is doing this, it is doing it when the engine is not under much load and therefore it is doing this when the engine is not under much danger of a slightly slightly slightly higher temp. In any event, any time you have a system like this malfunctioning, it is ALWAYS best to fix it and it is ALWAYS best to fix the part that is actually malfunctioning. In other words, do not just throw parts at the problem, follow the diagnostics in the FSM, determine which part is problematic and fix that part. There are so many here (including myself) who jubilantly declared that they fixed the 401 by replacing the modulator for example when in reality it was the VSV that was bad. In my case it was both the MOD and the VSV. Bottom line is fix it fast and fix it right. HTH.

 

[stevezero]

In my case, I replaced the VSV, EGR Valve, Modulator, and had a serious cleaning of the intake plenum and the tubing that runs down to the block. Fortunately, I had that work covered as part of my buying the vehicle. It took three tries for them to get it nailed, but they did it. The main two reasons I had them throw parts at it: I didnt want a CEL on a brand new to me vehicle(when the one i traded in was in excellent shape), and I didnt have to pay for it.

I've put 2600 miles on it since then with no 401 light.......

The longer you let it go, the more chance carbon has to get further down the system. If youre going to do the VSV, you might as well clean the intake plenum(since you have to remove it anyway),tubing to the block, and check the vaccuum lines. You can always keep the parts as spares if needbe.

Word of advice, if you clean the EGR parts, use very very very low pressure air. Youll blow it apart with pressure.