Trim450

Hoping to get some help here. Pick up a 07 j/k auto , no power locks or windows and has 73k miles. Jeep runs perfect until its warmed up then the dash lights start flickering and rpms jump up and down and the dinger is going off. I can keep it running with the throttle until I shut it down but doesn't want to idle.

So I shut it off and then it wont crank or nothing, it powers up and everything works but no starter. But if I get out and grab the roll bar and rock the jeep back and forth then it starts right up but soon continues the problem.

New battery and alternator, 14.5 volts to the battery when running, connections look good and runs great when it's cold.

Any idea where to start before I purchase a TIPM

Thanks in advance

Mr.T

Could be bad ground connection(s), especially since rocking the Jeep temporarily fixes it. Here's a few common grounds (pun intended) from memory to check, a search of the forum will get more details:

Around the perimeter of the engine bay just below the hood line (forward of the battery on the passenger side, and near the PCM on driver's side). A friend of mine had similar problems, and one of these was loose-corroded w/ bad connection.

Engine ground, it's on the passenger side of the block near the knock sensor. The engine end of the wire is hard to get too, some have added a (parallel) engine ground by running a new ground wire to the alternator bracket. There are several threads about this.

Inside the Jeep, left of the driver's left foot (below the OBD port, left kick panel).

Stay in touch, hope this helps

Trim450

Thanks for the info Mr.T , I did what you said and checked all the grounds I could find and they looked good and tight . Also it acted up last night as soon as I started it last night when it was cold and I noticed every time the lights and bell would go crazy the cooling fan would kick on high then off with the dash lights flashing . So I pulled both fan relays hoping it had something to do with those but no luck the gauges and lights still going crazy .

But still I can rock the jeep holding the roll bar still and make it start doing it or stop most of the time , so I'm thinking it has to be a bare wire touching somewhere.

Also the abs and brake lights are on though the pedal feels great and plenty of pads .

Should also add this thing has a 1 1/4 body lift and flat fenders with side marker lights mounted up under using the factory plugs , then I got to thinking the driving lights are missing in the bumper and I didn't have time to look for the wiring for those yet but was wondering if there in the same harness as the cooling fan . Just kicking ideas around in my head what it could be , I just bought this thing so really have know clue whats been done to it .

Thanks again for the help.

Mr.T

Sure is a weird set of symptoms. A few more thoughts:

If it's a Rubicon, disconnect the wiring connector at the swaybar for the e-disconnect and see if that changes the symptoms.

Actually take the ground lugs off, clean, look for wire damage, and assemble. Also double-check the terminals and connectors at the battery. Sometimes there is corrosion inside where wire meets the metal connector -- Wiggle connections like this and see if it makes the problem happen or disappear.

Take a single battery jumper cable and connect the battery negative to the engine -- The alternator bracket bolt is probably a convenient place. The idea is to add a ground to replace a potentially bad one. If that doesn't change the symptoms, try jumpering battery neg to one of the body grounds. Be careful the jumper doesn't fall into the serpentine belt, etc.

Using a meter to do voltage drop tests might help, but with an intermittent (maybe a high frequency intermittent) connection it may not help -- If you have a meter and know how, give it some thought.

It may be the TIPM. The part about it happening after the engine warms up points to temperature affecting something, but rocking the body points to a motion affecting it. If it's temperature, leaving the hood open should delay the symptoms if the problem is under the hood.

Visually look for wiring damage, critters seem to like chewing wire insulation.

Stay in touch, and good luck

Mr.T

Another thought: Since the ABS light is on (which is suspicious itself), disconnect the ABS and see if the symptoms change. Below is a screenshot of the connector and how to release it. Remove battery neg beforehand, and wrap the connector in something like a plastic bag to insulate the pins before connecting the battery again. Disconnect battery negative before re-connecting, and make sure it's clean. Mistakes here can damage stuff, so don't do this if it feels like it's outside you're skill set. This is far outside of any troubleshooting in the manual. Similar to removing the connector for the swaybar e-disco, the idea is to find a likely suspect to disconnect and see if the symptoms disappear or change -- The ABS lamp should stay on since it's disconnected and would appear failed to the rest of the system. Also, if the check engine light stays on try to retrieve the codes.

Trim450

Thanks again for taking time to help out , much appreciated.
Had a friend stop by and give me a hand tonight. The jeep would not crank or anything when I got home from work and has been setting since yesterday. We checked the grounds and jiggled plugs , harnesses crawled under and everything seemed good.
Then I tapped the ecm with a wrench and it started right up. After running a while it started its original problem and if I tapped the top corner of the computer it would straighten up and if I hit it again it would start acting up again
So I pulled the 4 plugs and everything looks ok there , plugs are good and tight so then hooked it back up but same deal.
Going to take the pcm in to work and pull it apart to see if its something can be fixed , we have a guy that repairs computer boards so may be a chance he can help , but if not I'll have to order one and hope it takes care of the problem.

Mr.T

Nice work, amazing what tapping and wiggling can uncover! Here's a link to a used PCM outfit on the internet in case you start thinking replacement.

tedhebert

[QUOTE=Mr.T;4339300]
Engine ground, it's on the passenger side of the block near the knock sensor. The engine end of the wire is hard to get too, some have added a (parallel) engine ground by running a new ground wire to the alternator bracket. There are several threads about this.

Related to this, my 2007 JK with 98K miles has been throwing a P0403 - EGR valve error code. My mechanic replaced valve - still throwing code - says it's only 30% open. Said take it to dealer cuz maybe their computer/code reader shows something different. HA!
Went to dealer - they said it's a corroded main engine ground wire - and to fix the issue they need to replace it entirely - and that means 8 hours of work (@ $125/hr) to take off cat converter, other parts, etc., to get at it. AND...they may break parts along the way and those would have to be replaced. This sounds like an obvious scam, but maybe you all know better? I like Mr T's idea of "adding a (parallel) engine ground by running a new ground wire to the alternator bracket." Any thoughts?

tedhebert

I added parallel ground today from neg batt terminal to alternator bracket bolt. Still get code. Tried clearing - came back. Now I have a new code U0184 -"Lost Communication with the Radio" - any suggestions? Thx in advance!

Mr.T

Here's what the manual has for U0184 possible causes:
Will the U0184 code clear? If it does (and doesn't come back) it's was probably related to work you did adding the ground.

Regarding the EGR, my suspicion is that although the batt engine ground may be visually corroded, it's not really a problem or even related to the EGR DTC. My reasoning is that a bad engine ground typically affects starting the engine, plus adding the parallel ground didn't fix it (BTW this could have been tested using a jumper cable as a temporary parallel engine ground). There is also voltage drop test that any good mechanic should have done during troubleshooting to test the engine ground, but if the problem was intermittent it won't necessarily be conclusive.

Here are the P0403 Possible Causes from the manual:
Important Edit: K35 (see above) is the dark blue wire in position 6 on the EGR connector, it goes from the PCM to the EGR solenoid. The black wire at position 4 on the EGR connector is the solenoid ground wire (to G104). P0403 is detecting a problem in this circuit, which includes the EGR valve, the PCM, and the related wiring/connectors.

Since the first mechanic replaced the EGR valve and the code persisted, I'd check the wiring visually first then get deeper into circuit troubleshooting as necessary. Keep in mind that the replacement EGR could be bad, or the connector/wire damaged during repairs.

Bottom line, the first mechanic probably took a troubleshooting shortcut and just replaced the valve and the dealer didn't follow the proper troubleshooting procedure in the manual either. It's hard to bill for troubleshooting and it's a complex art, so people often resort to a quick diagnosis for a likely part replacement and just hope for the best...

Dealers have access to the best equipment and all the manuals & wiring diagrams, the hard part is getting the right dealer with a really good electrical troubleshooter.

Stay in touch, hope this helps