Check Engine Light Off (P0401 "Fix"?) (1 Viewer)

[tarbe]

From the FWIW Department:

My cruiser had the light for some time prior to purchase. I ran some BG44K through, then some Lucas UCL. I pulled the old modulator and cleaned it manually...then finally put in a new modulator.

After I put in the new modulator, the light stayed off for about 500 miles, then came back on and stayed on. I know I should change out the other parts, but was spending my mad money on OME, tires and good stuff like that!

After about another 10,000 miles, I decided to run some Schaeffer's Soy Ultra fuel system lubricant/cleaner. I ran a 12 oz bottle per tank (their "clean up" dose) on three tanks over the course of about 8 or 10 tanks. The light went off on its own, and has been off for over 1,000 miles now...twice as long as when I put in the new modulator.

I am using the same fuel from the same stations as before.

Make your own conclusion! I think I'll continue to run a bottle through every month or so.

 

[RavenTai]

only problem is nothing in the EGR system is exposed to raw fuel, do you think this stuff could survive combustion? If so not sure I want to put it in my fuel tank

 

[tarbe]

It is exposed to combustion by-products. My guess is there are combustion by-products that are doing some "cleaning".

 

[Junk]

has been off for over 1,000 miles now....

Get back to us after a little more time.

 

[Bear80]

tarbe, where in the lone star state are you at? ignor:The cel is the check engine light, I took the 10,000 miles you said as that's how long you drove the wagon with the cel on.

 

[Bear80]

nevermind what I said, I didn't get it ther first time I read it.

 

[tarbe]

nevermind what I said, I didn't get it ther first time I read it.

You read it correctly...there was a 10,000 mile period where the cel was on.

During this time my mileage has been fine (for a lifted 80!) and I have had two oil analyses that had no fuel, little or no insolubles and great wear numbers.

I would be surprised to the max to hear that a cel for one sensor would result in an on purpose creation of other problems by ignoring most other engine management sensors. Why not just go into limp home mode? That way there is an obvious issue that you have to deal with. Low EGR flow by itself is not going to hurt anything except your chance at passing a smog test.

I'm struggling to understand how my vehicle could run this perfectly with the important engine management sensors caput?

 

[tiorio]

Is this 10,000 mile thing true? I've been cruising around with my check engine light on for a while now as well. Haven't noticed any detrimental effects...

 

[Bear80]

I may be wrong with the 80 but I know for a fact all my other toyotas will go into a "open" loop mode if the cel is on, which is what you refered to as the limp home mode. The engine only uses the "open" loop when it is first cranked then if all the inputs from the sensors are good it goes into "closed" loop.

Oh I have the same intermentant po401 light every now and again, the only thing I really notice is the shifts of the tranny. I don't know if the shift patterns are affected but thats just my seat of the pants feeling. Other than that the engine seems to run as good as if the cel was off.

 

[tarbe]

I can't say the shift points are any different. Honestly, I can't tell if the light is on or off except to look at the dash. It just doesn't seem to make any difference in any way I can subjectively feel.

Objectively, all the numbers are good.