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01 xj check engine light help

covey88

NAXJA Forum User
Location
ohio
ok guy i have a 01 xj with all stock motor wise minus intake and throttle body spacer(all installed before i bought), my jeep popped a p0441 code a while ago so i replaced the gas cap. the jeep was fine for 4-6 tanks of gas so 1000+miles with no check engine light, drove it 13 straight hours to north carolina (where i moved to) and now it popped the same code yesterday. how do i fix this code without blindly replacing parts. is there a trick to checking for a vacuum leak? also the tank is 1/4 to 1/2 tank full so have not filled recently. I need this fixed so that i can pass the out of state inspection and emissions check. Thanks for any ideas or advice that you guys have.
 
I've heard one way to find a vacuum leak is to take a propane torch and trace all the vacuum lines with the engine idling. The idea is the extra fuel from the torch will cause RPM to rise when you hit the leak.
 
I've heard one way to find a vacuum leak is to take a propane torch and trace all the vacuum lines with the engine idling. The idea is the extra fuel from the torch will cause RPM to rise when you hit the leak.
Be sure NOT to light the torch, LOL.
 
You know, you can get that code for something as simple as not seating the fuel filler cap tightly. I would start this way....pull the cap off and put it back on. Then check the charchol canister behind the driver rear tire, next to the fuel tank and see if you see any visible cracks or a hose that got popped off the nipple. Then pop the hood and follow all the vacuum lines from the exhaust manifold (on the 2001 there are 3 of them) and see if they are cracked or popped off the nipples. Follow those lines all the way over to the leak detection pump on the rear passenger side of the engine compartment between the fuse box and fire wall.

After checking everything, if you don't see an immediate error, or you fixed a cracked or loose line, detach both the + and - battery terminals, touch them together for about 30 seconds to reset the computer, the hook them back up and see if that code still comes on.
 
i already tried the gas cap idea with no luck. looked all over the lines under the the hood with no luck(also tried the carb cleaner sprayed on the vacuum lines), will have to crawl under the jeep and check the canister lines. will a smoke test be able to find the vacuum leak? and if i touch the +and- together want that short something out instead of resting the computer?
 
I got that on one of my '01s when the single-wall rubber connector hose between 2 sections of gray pvc piping back to the tank started splitting. The piping is part of the emission leak test parts.

Follow the gray plastic piping hand-over-hand from the pressure pump on the passenger side firewall to an area where the piping runs down the firewall on the driver's side. At the bottom of that run is one of the rubber connectors. It's probably split from heat. Replace it with double-wall fuel hose.

Then follow the line further aft under the body to where there is yet another single-wall connector. It's probably split from age. Replace that with double-wall fuel hose.

After learning that on my 1st '01, I replaced the same parts on my other '01. They were splitting too but hadn't started leaking.

Hope this helps!

(I prefer to use the code scanner to reset the computer. Touching battery terminals to anything makes me really, really nervous.)
 
Be sure NOT to light the torch, LOL.

Oh come on! I have heard the torch works better than anything, you find the leak, Jeep explodes, call insurance company, and get a new Jeep with no CEL problems.

But seriously, we have seen some problems with aftermarket caps, if you have IM testing in your area that requires a cap test try that, otherwise you may want to try the dealer route.
 
i already tried the gas cap idea with no luck. looked all over the lines under the the hood with no luck(also tried the carb cleaner sprayed on the vacuum lines), will have to crawl under the jeep and check the canister lines. will a smoke test be able to find the vacuum leak? and if i touch the +and- together want that short something out instead of resting the computer?

he's saying to touch the battery cab;es together, not the terminals on the battery. I'd just disconnect them and then go turn the key to "ON" it will also drain the caps in the computer.

a smoke test will find the leak as long as it's a line and not something internal to the canister or in the tank.
 
he's saying to touch the battery cab;es together, not the terminals on the battery. I'd just disconnect them and then go turn the key to "ON" it will also drain the caps in the computer.

a smoke test will find the leak as long as it's a line and not something internal to the canister or in the tank.

If it was the leak detection pump, it should throw the code he is getting as well as a 1494. I would bet that with only one, extremely generic code, it is something fairly minimal...like a split or a bad connection...versus failure of a part. My opinion...for what it is worth...

And yes, just touch the cable clamps together. Stay away from the terminals. As a matter of fact, just to add a level of safety and comfort, anytime I have a battery cable disconnected from the terminal I put a shop rag over the terminal to ensure there is no accidental contact.
 
ok will check those lines, does anyone have pictures of these lines? the previous owner undercoated the whole jeep, so it is hard to tell the difference in the lines.

Cottontail i am praying you are right, that it is just a very small issue. specially since i just moved and money is tight.

and can someone explain to me how touching the -and + cables together will rest the computer. I have always just left them unplugged for about 30 mins.

and does anyone know how long i have to drive the jeep before i can get it tested after i rest the computer?
 
Computer reset is best watched with a scan tool. The rules for the system doing self test and completing have to do with cold start, outside air temp, fuel tank level.

If the lines are covered with gunk your best bet is to look for a short section where it looks like a rubber jumper is connecting two runs of piping.
 
and can someone explain to me how touching the -and + cables together will rest the computer. I have always just left them unplugged for about 30 mins.

Yes it’s a bad idea, don’t do it. Some urban myths just will not die, like unhooking the battery with the engine running to test alternator, another great way to destroy an ECU. Look if you open your car door with the battery unhooked you will have drained the cap in the ECU with in a split second, why risk damaging components?
 
Yes it’s a bad idea, don’t do it. Some urban myths just will not die, like unhooking the battery with the engine running to test alternator, another great way to destroy an ECU. Look if you open your car door with the battery unhooked you will have drained the cap in the ECU with in a split second, why risk damaging components?

To drain the capacitors holding a charge you have to short the positive side of the circuit to ground. I don't see how opening the card door or turning on the headlights, when the battery is disconnected, that the circuit will be completed. With the battery disconnected, the positive side of the circuit is not connected to anything.
 
A cap is battery, any electrical load that is not key on will drain the cap, so key off, disconnect battery, open door, cap drained.
Touching the positive to the negative results in an arc, caps are not designed to completely discharge that fast and can damage them as well as the chance for a voltage spike which can damage the ECU.

You may get lucky but if you are going to try it have a spare ECU on hand.
 
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