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Uniblurb 07-24-2013 04:12 PM

Check engine light on but no codes??
I just bought a 2004 4.7 Limited w/74K miles from a dealer a couple weeks ago and have hardly driven it. Today I took it for a short 5 mile drive and on the way back the "Malfunction Indicator Light" came on which is just great. Before I even shut it off when arriving home I put my scanner/reader on it and no codes were found. I then shut it off, waited 30 secs, started it and the check engine light is still on. It seems to be running fine with maybe just a few slight misses.

I read the owner's manual and the light isn't flashing indicating a serious problem. I checked the gas cap and it seems tight. I'm not at all familiar with WJ's and does anybody have any tips what the problem may be? Thanks!

Uniblurb 07-24-2013 09:45 PM

Any help please? I'd rather not have to return my WJ to where I bought it and fix it myself.


gcjeeping 07-24-2013 09:49 PM

Did you try the on-off-on-off-on key trick to show codes on the odometer?

Did you try and just do an erase codes( I know it didnt show any )?

Uniblurb 07-24-2013 10:17 PM

No I didn't try the key trick and that would show a code where a scanner/reader wouldn't?

Haven't yet erased the code(s), if there are any, because I want to find out what it is first.

Thanks for the input!

Uniblurb 07-24-2013 10:33 PM

Well I ran out and did the key trick and it showed code P0700. Isn't that some type of transmission/transaxle problem?

pinky2252s 07-24-2013 10:39 PM


Originally Posted by Uniblurb (Post 15716056)
Well I ran out and did the key trick and it showed code P0700. Isn't that some type of transmission/transaxle problem?

Yep. You have to get the transmission codes read by a DRB3 scanner.

Uniblurb 07-24-2013 10:54 PM


Originally Posted by pinky2252s (Post 15716072)
Yep. You have to get the transmission codes read by a DRB3 scanner.

Well, that's just swell and guess I'll take it back to the dealer where I just bought it. It's supposed to have a drive train warranty good for up to 100K miles (26K to go) so will probably taking them up on that. Of course it has a $100 deductible which is not good.

Before taking it the 80 miles round-trip to the dealer I'm going to get under it and make sure one of the bushy-tailed rats around here hasn't chewed a wire in half! One of the drawbacks of living in the woods.

Thanks for the input!

bradywgn71 07-24-2013 11:05 PM

It doesn't have to be a DRB3 to pull the code. I had a P0700 recently on mine. I took it to O'Reilly's Auto Parts and they pulled the code with their scanner for free. Turned out it was a P0734 code. Try Autozone or one of the other local parts stores that will scan codes for free before paying a $100 deductible.

Uniblurb 07-24-2013 11:21 PM

So evidently their scanners are better than the $100 Actron CP9575 OBDII scanner I have which showed nothing? I'll give it a shot since have an appt to get new tires tomorrow near both those auto parts stores. Thanks!

So what is code P0734 you had on yours? Is it going to hurt driving mine with just a P0700 info code on mine?

rdkendrick 07-25-2013 07:06 AM

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Uniblurb 07-25-2013 06:50 PM

Thanks for the link!

Well, I went to both Advance & Autozone today today and they were both able to bring up code P0731, Gear 1 ratio incorrect, on my 2004 4.7 Limited. I did some searching and found often the input or output speed sensor is normally the cause but which one?

Since only owning this WJ for 13 days I called the dealer salesman who told me to call the sales manager. Sales manager routed my call right back to the salesman who said I need to call service and make an appointment. Stupid me forgot to ask if the repair would be covered under the 100K drive train warranty. And if it is there's probably a $100 deductible.

Since there's supposed to be a 14-day no hassle return policy I should just call them back and tell them I'm bringing it back tomorrow while wanting my money back if this repair is not done at no cost! Kind of a false threat since I just had $900 of tires installed today and should have waited until this trans problem was resolved.

After new tires were installed I took it in for an alignment and the nice old-timer mechanic showed me where the lower/left ball-joint was bad. Said he can tell it was just aligned but told him I'd replace the lower/upper ball-joints and bring it back for alignment check. Didn't charge me a dime and we looked at the wiring on the speed sensors which looked fine.

Is it a crap shoot if I just try replacing the speed sensor with a Mopar one myself to see if the P0731 code disappears? Saw one thread which said both input/output sensors are the same part and just buy one while switching them until problem's solved. Half afraid to damage the tranny in driving it since it's now shifting pretty darn hard from 1st to 2nd.

Thanks for any input!

Schlotzky 07-25-2013 07:22 PM

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There are fail-safes for the transmission, so as long as you're careful and don't go months without fixing it, I wouldn't be too worried about further damage. If you have a multimeter, I know you can test the resistance on the sensors and determine if they're good. You should read about 0.5 Ohms on a good sensor, and a bad sensor will likely read "open" if you put the multimeter leads to the two pins. If you can determine which (if either) is bad, you can replace the part in a few minutes for less than that $100 deductible. But see if you can get the dealer to do it for free first for sure.

Uniblurb 07-25-2013 07:48 PM

Real good idea testing the sensors 1st and thanks for the .5 ohm spec! I'll test them tomorrow and check to make sure the the connectors/plugs aren't corroded too. Yeah, I'll go the free route at the dealer if at all possible. Hate dealing with those people and wouldn't have even bought it there if not such a good price ($10K w/74K miles).

Double E 07-26-2013 04:27 PM

Good info here. It probably is the SS. When it goes, the other one is probably not far behind. If you get an aftermarket one for a good price, pick up a 2nd to have so that road trip you take is not ruined... Test it, then replace and keep your c-note if they're going to charge you anything.

Uniblurb 07-27-2013 02:31 PM

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Thanks for the info/advice! I called a parts guy I know real well at the local dealer yesterday who runs the parts department and gives me a wholesale discount. He confirmed the input/output speed sensor on the 545RFE are one in the same and said he had a set in stock. List is $43/each and with my discount it would be $32/each plus tax.

But the more I thought about it the more it ticks me off after only 10 days of buying this WJ from the dealer 40 miles away I was being blown off by the used Jeeps sales manager jerk. I called the director of sales, plead my case, and he's going to waive the $100 deductible while saying the speed sensors should be covered by their drive-train warranty. I have a service appt set up for Monday.

Since there's no service records on my WJ I was thinking about asking them to change the trans fluid/filter while I have it in there. But I'm sure they would charge me an arm and a leg to do this while this is normally the type of maintenance I do myself.

I have the FSM but there's no section for changing the fluid/filters on the 545RFE. Any tips/tricks on DIY and read something about problems with the cooler return filter seal/o-ring? And in looking at the 2004 WJ parts list are the cases/parts the for the 545RFE and 45RFE exactly the same? I'm seeing OE item #15, "Filter Package, Trans Oil", 6503232 on the below figure. Wonder what's included with the "package" and thought this was just the primary filter? Is item #17 the correct cooler return filter (4799662)? They don't list any pan gasket and anybody know what the OE # is or should I just go with something like Felpro?

If I drain the trans with filters removed how much ATF should I need? And guess any kind of ATF+4 will work and I've been using Valvoline MaxLife lately since it's only $17/gal at Walmart.

Below is the figure, sorry for all the questions but I'm new to WJ's, and thanks for any help!

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