25th Mar 2010, 21:48

2001 Jeep Cherokee code 303... a few things can make this code show up, from misfire to coil pack, to low or high gas pressure, so they say... my light came on again, (few times) and every time it comes on, I notice a big drop in gas mileage. The only thing I have not changed was the gas cap.. Does that have something to do with high or low pressure??? Anyone have any ideas??? I tried everything I know, so now here I am asking you guys for help.

31st Mar 2010, 11:55

These are awesome posts! I have a 2001 Cherokee Sport with 130,000 miles - the check engine light came on at 127,000. Took it to Auto Zone and they checked the codes for free for me. If you are getting a P0303, you might also get a P1494 code as well? I couldn't figure out what mine was doing, since it just had a major tune up, so I called my friend who is a mechanic and he suggested I check the O2 sensors on my vehicle. The manufacturer recommends replacing every 100,000 miles, and mine were original parts.

I did some research and purchased all 4 brand new 02 sensors online for about $45 a piece. (if you go to a Jeep dealer, they will cost about $90 to $100 a piece) Replaced the 02 sensors and the Check engine light went out. Make sure you get OE parts with the connectors already on them. But this is an easy to do job and it fixed my problem.

I did also find out that there is a service bulletin out on the intake manifold - safety recall. 1999 through 2002 models. They will install a debris shield on your intake manifold for free; just go to the Jeep web site and look up recalls for you vehicle, print up the form and take it to the dealership with you.

The 02 sensor part #'s are:





The original parts are NTK (I believe), but Bosch and Denso make great replacements as well.

21st Aug 2010, 17:34

For those that are having problems with power windows, I have a 2000 Cherokee that had the same problem, and ended up taking the door panel off and unplugging the group of wires that go from the cab threw to the door, and found that several were broke. A connector with heat shrink to reconnect the broken wires fixed the problem, and I did both the driver and passenger doors.

15th Oct 2010, 11:50

I have a 2001 Cherokee Sport with 120,000 kilometers on it. Bought it 2 years ago with the engine light on. The mechanic told me the code meant something was wrong with the emissions control, but could not fix the problem. The engine ran fine, but sometimes when in idle, it felt a little rough. One morning I noticed a whistling sound, which I interpreted as a vacuum leak. I finally decided to take matters into my own hands, and got on the floor and started checking every vacuum hose from the underside of the engine. Right behind the brake booster (left hand side), I discovered a 5/16" vapor hose coming from the fuel tank. It looked fine from the top, but was dry cracked from the side facing the firewall (only visible from the underside). I changed the hose and disconnected the battery to reset the engine light. Voila! It has been two weeks and the engine light is off. The engine runs smoothly, the whistling sound disappeared, and the gas mileage has greatly improved. Hope this fix works for you. I love my Jeep!

25th Oct 2010, 07:24

Blimey, just bought a cool black 1998 Cherokee Sport 4.0.

It's great - apart from a splutter and misfire at low speeds/revs. Replaced already injectors, sensors, dizzy cap looks new. Will probably put a cleansing petrol additive this week to see if that helps...

Thanks for all the other ideas. Anybody else had this specific problem and has a quick fix? Any help appreciated.

Paul, Barcelona, Spain - Jeeps are considered exotic imports over here!

25th Oct 2010, 18:54

2000 Jeep Cherokee Sport.

Love my Jeep, but it recently started over heating. Changed the thermostat, but it is still getting too hot. The connector to the AC line coming from the passenger side of the radiator's leaking steam, and the bottom radiator hose is cool, as is the cap. The water pump will be replaced next in the hopes that fixes it. Any other suggestions as to what might be causing the problem would be welcome.

18th Jan 2011, 16:19

On January 8th of this year, I bought a 2001 Jeep Cherokee 4X4 auto Inline 6 at a local used car dealership in Boise, Idaho.

After driving it three times the CEL came on today and stayed on. I did the "hold-in-the-tripometer-while-turning-the-key" thing and got nothing but mileage after it went through the 11111-9999 stuff, but never gave a code.

I'll try the "disconnect the battery" trick to see if it helps.


9th Feb 2011, 20:34

Same thing with me, I have had my CEL on many times and usually just take it to Autozone and they run the diagnostics for free, take the error code and enter into system to get your problem. This avoids charge from dealer or garage.

I am unsure my error code #, but I did the odometer hold down as well it just went through the 11111-99999 which I didn't know about until this post but I still ended up going to Autozone.

My error was leak detection pump/emissions error. Fixed CEL which is now off for 100+ miles.

Current mileage on 1999 Cherokee Sport 2x4 4.0 6L is 177,xxx.

Hope this helps folks. Good thread.

22nd Mar 2011, 12:24

Mine is doing the same thing, did you ever get yours figured out?

9th Apr 2011, 20:58

My son's 2001 Jeep Cherokee engine light comes on. Well this is his second Cherokee that this happened to. What we did to get it off was to disconnect the positive battery cable for about 30 seconds, and then while it was off, turn the key to on, but not start 3 times, wait 30 seconds, and connect the battery. The light will be off. Trust me, done it many times on many cars.

23rd Apr 2011, 19:14

Mine did the same thing. I took the door skin off and found that the plug to the switch was loose.

1st Jun 2011, 12:38

I own a 2001 Jeep Cherokee Sport 4x4 with the inline 6 motor.

I have problems with the engine light coming on. I live in NC which has inspections on vehicles every year, so when it has been taken to get inspected for the year, it fails with the following: failing Evaporative System/O2 Sensor Heater. Unplugging the battery for a few seconds does no good as it resets the computer, but also resets all the codes, so none are ready for inspection. I'm at my wits end trying to figure out what to do so I can get my Jeep inspected and drive again.

Other than this issue I love my Jeep and wouldn't own another vehicle. Any ideas?

1st Jun 2011, 15:06

Do searches on some of the many XJ based sites on the web, if you have the code (CEL) #. Some of the more common sites are:




9th Jun 2011, 18:08