check engine light

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Jan 2, 2003
Dweller on the Threshold
Live and learn. I've scanned the archives. I have a 96 fzj80.
Yesterday I overfilled the gas tank and when I started the
truck up the check engine light came on. It has stayed on.
I'm going to have the dealer read code for me tomorrow. OUCH!
At least this board has me prepared for the sticker shock.
I'm going to order a scanner of some type a.s.a.p.
Could an overfill cause the CE light to come on?
I can't be that "lucky". Truck runs great. My wife's eating
rolaids tonight after I told her about needing a scanner for her
"new" truck. Lord only knows how she'll react when I tell
her what the "reading" costs are from a dealer.
Thanks for this forum. I can see already that I'm going
to be at a loss without it and it's archives.
I'll probably return with some code numbers soon.
harbor freight tools code reader: $40

Before you and the wife get an ulcer, slip out in the garage, loosen, then tighten the gas cap until it clicks 5 times. Then pop the bonnet, pull the EFI fuse (in the black box aft of the battery) leave it out for 30 seconds, put it back in, close the bonnet, and start the engine. That will clear the MIL (Malfunction Indicator Lamp aka Check Engine lamp.) The engine might run rough and idle erradically for a day or two as the ECU relearns the fuel management settings. Most vehicles run OK within a few minutes.

The OBD-II system in your 96 is designed to keep after you if there is a code of some significance. In other words, clearing it may work indefinitely, and if something is "wrong" then the system will re-post the code and turn the MIL on again. Don't sweat it as almost all the OBD-II codes are emissions related. Those that are not will happen again soon (engine misfires, etc.)

If it happens again then take it to your local Autozone, as suggested by Rick, unless you are in the PRC in which case you'll have to find another way to get the OBD-II code scanned.

The code will be something like P0401. Be sure to get the exact code and don't let them say "it's the EGR valve" or something like that. The actual code is important.

B -

>> PRC...

People's Republic of California ?

R - :D
that's the polite version, for the rest of us it's PRK! grrr....
Well...I went by an Auto Zone today while working out of town.
I got my free code reading. They won't cancel the check engine light.
Pulling the fuse didn't make it go away either. ;) Grrrrrrrrr
The code was 401.
Now my wizen and learned friends what the heck does that mean?
The guy said other than that code all was well.
He ventured a "guess" that it could have been my over filling
of the gas tank.
I 'm betting that wasn't it and it was just a conicidence that
it came on when I filled to overflow.
What do I do now?
They were out of there scanners for sale. ($150)
I'm thinking of checking with Harbor Freight for the $40 version.
TIA for all ya'lls help,
I remain clueless in Pumpkintown,
Someone will be able to tell what a code 401 is. Even the haynes book will tell you what that is.
I bought a Haynes manual the day I bought the truck.
It's for 80-96 60s, 62s, 80s and FZJ80s.
Chapter 6 listd codes. NOT the codes for a 96. Grrrrrrrrr
They are all 2 digit codes listed and this is a 3 digit deal.
I guess I'll be buying a factory manual to go along with that scanner I'll need. ;)

Code P0401 is well known to this group. There are dozens of messages, threads, in-depth analysis, fixes, work-arounds, etc. Over filling the gas tank did not cause the P0401.

P0401 is EGR flow insufficient (or something like that.) EGR = Exhaust Gas Recirculation

Bottom line is that you have an emissions related code. It is very unlikely to effect the driveability of your truck. Many of us have driven for months and months with a P0401 (approx 1 year in my case.) There are 4 parts and several hoses in the EGR system. The EGR valve, the EGR modulator, the EGR temp sensor, and a Vacuum Sensing Valve (VSV.) Plus interconnecting wiring and hoses. Read the archives and dive in to the problem isolation. It could be any of the parts mention.

Pulling the EFI fuse *will* clear the CE light. It might come back... but if you did it correctly, the MIL will be cleared. Trust me. (Corrected)

P0401 is EGR insufficent flow.
Gundy, I just had one of those - also 96/97 (I was told, but have not done it this way) might not necessarily reset code after pulling fuse. PO401 Means your EGR valve is not recirculating enough exhaust gas - this could mean slightly higher exhaust temps and more wear on the cat but would not likely cause your truck to run poorly. (Emissions related) I was told by mech that the egr valve needed to be replaced - doing reading, including part and replacing labor was quoted at $160. 401 is a 2 trip code meaning the problem has to appear twice before check e light comes on. You could try cleaning yours (search archives) or buy one and replace it yourself, you will still need to reset your code and you might need to buy a reader to do it (or borrow one). I have Kragen base model $125 it works and can reset code or not. Or you could drive around that way for a while . . .

PS - most code readers come with a manual that explains the codes - some are better than others
Thanks B. I'll do some archive searching. Looks like I'll be replacing
some emissions stuff. Thanks for getting me started.
You guys have enabled me to calm the wife's fears of
a motor meltdown. She's off the rolaids. ;)
Thanks to all for bearing with my newbie questions.
I'll try not to abuse this valuable resource.
I have a OBDII reader from . The BR-3 is $88 shipped. If you have a laptop, this is the best bang for the buck.
Great features.

Gundy, not to bore everyone else, but I'd pull the egr temp sensor and clean it first. This is the device that senses wether or not there is enough flow. A dirty sensor will give a false code. A no cost first strike at the problem.
As long as you're doing quick-fix cleaning, pull the cap off the EGR modulator and use compressed air to clean the little round "filter." That didn't do anything for my truck but some have cleared the P0401 with this no cost trick.
Hey -B-, if one pulls the fuse and successfully clears MIL, does the computer retain a log of this? I read that some of the fancy (professional) scanner/readers (particularly used for smog checking) can see a past history if a MIL was cleared or if a code was read or ...? Does pulling the fuse completely wipe clean the computer history/memory?
>> Does pulling the fuse completely wipe clean the computer history/memory? <<

I'm not sure if it clears out everything, but it will turn off the MIL (check engine light) and resets the "drive cycle" We've had discussion on this in the past so if you want more details you can do an archive search. I believe Gumby posted a lot of detail.

Basically, the OBD-II system keeps track of a "drive cycle" and pulling the EFI fuse resets this. When you go in for an emissions test they can tell that the vehicle has not completed the "drive cycle" and some states will not pass the vehicle. Many of the emissions checks in the OBD-II system are two trip logic and those trips have to go through certain conditions; target speed, duration at the target speed, coolant temp, etc.



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