26th Nov 2010, 17:15

I have a 1998 Jeep Grand Cherokee 5.9 Limited. Recently the headlights started to stay on ALL the time. The only way I can get them off is to disconnect the battery every time I turn off the ignition. I have been told that this could be due to the Daytime Running Light module, and also told that if I disconnect it, the problem will be solved. Does anyone know where this is located? It has about 225,000 km on it.

8th Feb 2011, 21:58

I have owned the 5.9 since year 2000. For problems with pinging and no 93 octane gas available; the dealer can reprogram the software for the engine to run on regular fuel. Then you can run regular gas, or premium higher octane any time you want the extra power or need to tow. This re-programing stopped forever all my pinging problems.

My 5.9 now has 162,000 miles. I have replaced just about everything around the engine. PS the vicious coupling issues in the transfer case that causes front wheel binding can be caused by not having the correct size tires. You should never run oversize tires on this car, it can and will damage the transfer case components.

27th Apr 2011, 18:19

Agreed. I couldn't have put it any better myself.

27th Apr 2011, 18:41

It's been over a year and a half. Have you upgraded to the 6.7 yet?

27th Apr 2011, 18:46

93 ONLY!!! It says right in the owner's manual :)

30th Jan 2012, 22:17

I too am in love with the styling, luxury and power of the 98 Jeep Grand Cherokee 5.9. I have purchased three black ones, one that my wife drives with 72K miles on it (had 55K when bought 3 years ago), and the other two are in storage, with one having 54K miles and the other 49K miles. I don't even drive them, but just knowing that they are there and I "could" drive them is enough to get me through the day. OK, sometimes I get to drive the wife's car when it's date night. That suffices my need. Now it seems I don't see any for sale with less than 100K on them... All mine are stock, no cold air, no chips.

31st Jan 2012, 10:48

Yes. The viscous coupling in the transfer case locks up when there's a difference in front and rear axle speed. This happens if your tires aren't pressurized enough. There should be a little bit more up front than rear. Measure the distance from rim to the ground on all wheels, and make sure it's the same.

Good luck.

17th May 2012, 13:24

Hi folks,

I just purchased a 1998 JGC 5.9! It has about 120k miles... very good condition, too. It's slate colour. I bought it off a 77 year old gentleman...

I'm glad I read all the posts on this site, it's helped a lot.

Cheers, James.

21st May 2012, 18:46

Wow, you have a couple in storage?? Let me know if ever you decide to sell one: jbarnard@scooterbag.com

22nd May 2012, 08:07

I agree that you should stick with stock size tires with this Jeep; you don't want to take chances for the sake of appearance. In fact you should make sure tread wear is even between tires as all. For example, if you have to replace one tire, and the others have noticeable wear - replace all 4.

20th Feb 2013, 08:15

Take it to Autozone to have the alternator checked out.

5th Oct 2013, 16:19

I own three 5.9s, because two are always under repair. I maintain that the 5.9 is the greatest “muscle car” ever built, mainly because it is AWD, which all the others were not, and the functioning hood grilles, which are rare on any muscle car.

When you stand on the accelerator of the 5.9 in deep snow, it doesn't spin off the road, it just moves side to side a little and takes off. Try that on a 2WD muscle car! Plus I pass cars 5-6 at a time on the two lane road to my ski area. 0-60 isn't the important specification, 60 to 110 is.

9th Jul 2014, 20:18

I had the same problem, and it was a broken shock or strut. I can't remember which it was on the Jeep. I replaced it and it works just fine now - no more clunking.

1st Sep 2014, 15:33

Had a lot of the same issues. You have a 2 stage fan and one may not be engaging. Also, my 5.9 only likes high test gas; if I run low grade in it, it will tend to run hot and that makes my trans act up, sometimes losing OD and sputtering like water in gas and wanting to stall at stops. My fan was was gunked up, and worked again after cleaning it up, and both stages worked again. Besides that, my temp issues and trans problems went away once I started running high test gas on a regular basis. I hope that this helps. Let me know.

1st Sep 2014, 15:48

I also have heard that some of the older Ford Taurus had the same fans; not sure if it's true or not. Good luck with the coolant sensor message; haven't been able to get mine off the board. I heard it's just a glitch in the system and typical of the 5.9. Will a 5.2 fan work?