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Old 05-31-2013, 06:05 AM
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Flat Towing Problem – Jeep Grand Cherokee 2014

<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <wontGrowAutofit/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--> One of the things that should be known after starting to flat tow a vehicle is how long its battery will last.

I use the Air Force One braking system; it’s an air system. This system uses no power during normal towing. The vehicle was set up for the days towed per the operator’s manual: after the transfer case was placed in neutral the push button ignition was placed in the “OFF” position which put the transmission in “PARK”.

First flat towing: towed 2.5 hours to destination; used vehicle. No problems.

Second flat towing: towed 2.5 hours to destination; used vehicle. No problems.

Third flat towing: towed 5.5 hours to destination; did not use vehicle. Left vehicle mechanically and electrically attached to MH overnight. Do not know of problem because did not use vehicle.

Forth Flat towing: next day towed 2.5 hours to destination; used vehicle. Vehicle started without hesitation. When started vehicle instrument display filled with warning lamps that would not go away: engine warning lamps, air bag service lamps, traction control lamp, ABS lamps, emergency brake lamps, both pass and driver side rear seat interior lights and seat belt lamps. Even with all of these warning lamps the vehicle ran normally.

With the help of our Florida Jeep dealer we found a Jeep dealer in Stone Mountain, GA. The Gwinnet Chrysler Dodge and Jeep Ram dealer provided us excellent service. We arrived at their shop at 4:00 PM and they connected the vehicle to their diagnostic computer. The fault codes were low voltage and communication loss. They cleared the codes and test drove the vehicle.

The engine warning lamp continued to show a loss of communication code. The assistant service manager said these vehicles are still new to them but he believed that after driving the vehicle for a period of time the vehicle computer would clear this communication loss fault and the engine warning lamp would go out. We returned to the campground; about 12 miles; the engine warning lamp remained on. I turned the engine off and gave it five minutes (just because!) and restarted and engine warning lamp was gone.

What is using power while the vehicle is being flat towed? Another way to ask this question is what is the difference in power consumption for the vehicle parked in our garage for two days verses being flat towed?

Two dealers so far would not even venture a guess.
  • I am thinking that even with the transfer case in neutral, the ignition in “OFF” and the transmission in “PARK” when the vehicle starts rolling the computer(s) must turn on.
  • Also when our braking system pushes the brake petal will that also activate the computer even through the ignition is “OFF”? (With the ignition in “OFF” and the brake petal pushed the brake lights will not work.)
  • It doesn’t seem reasonable that the computers would use that much power over a two day period.
  • And what is the computer’s low voltage threshold?
  • We had a low voltage code and yet the vehicle started without hesitation?

To help reduce power consumption I turned off the two features that turn on the head lamps for 30 second intervals: (1) at entry (2) departure headlamp 30 second “off” delay.

First attempt to solve the problem, assuming the problem is low voltage: I will install a battery charger so that the battery will receive a trickle charge while being towed. And alternative method would be to periodically start the engine to charge the battery.
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Old 05-31-2013, 07:28 AM
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Re: Flat Towing Problem – Jeep Grand Cherokee 2014

Did the dealer actually check the battery to see if it was discharged? It would take one minute with a ten dollar voltmeter.

The assumption that the battery ran down while being towed and connected to your MH overnight seems right to me too, but its still an assumption. With these new electronics, who knows?
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Old 05-31-2013, 08:23 AM
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Re: Flat Towing Problem – Jeep Grand Cherokee 2014

Yes, the dealer checked the battery with a battery checker tester and declared it good The dealer also said that if you leave an interior light on overnight the battery will run down. Since I've done that on other vehicles it makes sense. What I do not understand is how did I get a low voltage fault code and the vehicle start without hesitation? So far I haven't received an explanation.
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Old 05-31-2013, 09:05 AM
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Re: Flat Towing Problem – Jeep Grand Cherokee 2014

The jeep will not let the lights stay on. I have tried to keep the lights on while camping and it will automatically turn them off. I assume it has a low voltage cut off to battery power.
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Old 05-31-2013, 09:16 AM
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Re: Flat Towing Problem – Jeep Grand Cherokee 2014

I understand about the timer to shut off interior lights; very helpful feature. Just using an analogy trying to explain to myself why the battery discharged after two days of flat towing with what I initially thought was nothing turned on. Obviously I was wrong about that. Now trying to understand how much is being turned on behind the scenes with the ignition switch in the off position.
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Old 05-31-2013, 09:46 AM
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Re: Flat Towing Problem – Jeep Grand Cherokee 2014

My 14 had the same warning scenario, twice. Most of the warning lights went out the next day, but the check engine took two days. While all the warning lights were on the speedometer did not work.

On the first visit to the dealer, check engine had gone out by then, the car spit out a couple of codes that Jeep said indicated a bad ground, and referenced a STAR case. Everything looked good for a while, but then the same thing happened. This time, again the check engine had gone out, the Jeep spit out 2 pages of codes. They sent a new PCM which was installed last Friday, and so far so good.

I was told that the check engine light will go off after 3 or 4 starts if the fault is no longer detected. Even with the two pages of faults stored, the Jeep ran like there was nothing wrong once the lights went out. That's what led them to the PCM, because if all those faults were real, I would have been sitting on the side of the road.

Oh yeah, no flat tow involved.



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Old 05-31-2013, 10:17 AM
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Re: Flat Towing Problem – Jeep Grand Cherokee 2014

No clue what is using power while flat towing.

Not sure why, but the O.M. states the following under "recreational trowing":

If the vehicle is equipped with Quadra-Lift™ air
suspension, the engine should be started and left
running for a minimum of 60 seconds (with all the
doors closed) at least once every 24 hours. This process
allows the air suspension to adjust the vehicle’s ride
height to compensate for temperature effects.

Do you have QL?
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Old 05-31-2013, 10:29 AM
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Re: Flat Towing Problem – Jeep Grand Cherokee 2014

No OL. Bill de problems mirror mine and may explain why I started up. We'll tow again Sunday so will see what happens.
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Old 05-31-2013, 10:54 AM
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Re: Flat Towing Problem – Jeep Grand Cherokee 2014

Quote:
Originally Posted by SteveCG View Post
Yes, the dealer checked the battery with a battery checker tester and declared it good The dealer also said that if you leave an interior light on overnight the battery will run down. Since I've done that on other vehicles it makes sense. What I do not understand is how did I get a low voltage fault code and the vehicle start without hesitation? So far I haven't received an explanation.
Sounds like another wacko computer, maybe unrelated to the flat towing. If the dealer said the battery was good plus the engine started right up then you did not run the battery down flat towing.

Did they check the ground strap?
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Old 05-31-2013, 05:33 PM
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Re: Flat Towing Problem – Jeep Grand Cherokee 2014

I don't know if they checked the ground strap and the write up doesn't mention it. If you can point me in the direction I might be able to check it for obvious looseness.
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Old 05-31-2013, 10:09 PM
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Re: Flat Towing Problem – Jeep Grand Cherokee 2014

Another bad ground ? Is this an Overland or Summit ?
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Old 05-31-2013, 10:11 PM
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Re: Flat Towing Problem – Jeep Grand Cherokee 2014

Just curious. You didn't say how your tail lights/brake lights were wired on the tow vehicle. Did you put in separate light bulbs or did you cut into the wiring and use diodes on the factory lights?

Don't know what impact that would have but if you used diodes that would appear to be the only cross connect between the coach and the jeep system and diodes do sometimes fail.
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