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Posts posted by dhj1974

  1. Jeep N23 Recall problems

    For starters, I have a 2006 Jeep Grand Cherokee Limited that I purchased new as a vehicle to tow behind our RV. I have had no problems towing this vehicle 4 wheels down for seven years until getting the Jeep N23 recall fix. Since then it will periodically give the message to Service 4WD System when doing the procedure to put it in 4WD neutral for towing.

    We have actually had to leave our Jeep on the street when we had a service appointment for our RV 120 miles away because we couldn't tow it.

    It doesn't take much to find that there are thousands of people affected by this problem as quick Google search for Jeep Service 4WD System gets thousands of hits. The first few zero in on the problem for many started after getting the N23 recall fix. It turns out that after the fix the affected vehicles will eventually not be able to put the vehicle in 4WD neutral for towing or in 4WD LOW for off roading.

    The reason for the recall is that a cracked circuit board that controls the 4WD Low and 4WD Neutral can cause the vehicle to go into neutral when stopped in park. This could result in the vehicle rolling away when parked across a parking lot or worse, down a hill. That of course, assumes that people dont use their emergency brake when parking.

    So instead of fixing the cracked circuit board Jeep came up with a software fix. You DON'T FIX CRACKED CIRCUIT BOARDS WITH SOFTWARE. So what did they do? Apparently they fixed software in the FDCM the Final Drive Control Module. The FDCM is a different component that apparently takes instructions from the cracked circuit board, but has the ability to override that board. When you have different electronic components that communicate with each other that is usually called a Distributed Control System. It is distributed because each module takes care of its own function so you dont need one big computer running everything. So it appears the circuit board that might crack controls the 4WD Low and neutral and the FDCM transfers control to that module when that function is needed.

    I work with DCS systems, my guess is that the reprogramming of the FDCM added some diagnostics that check for signals from the board that controls 4WD Low and neutral. When the signals indicate the board might have the crack that initiated the recall, the FDCM prevents that board from ever taking control of the 4WD drive system. When you try to use 4WD low or neutral you get the only message that was available in the FDCM to display Service 4WD System. This is a cheap patch that doesnt fix the problem a cracked circuit board that should be repaired or replaced.

    The internet is full of how to temporarily fix this problem. You open the hood, find the fuse box with the FDCM fuse, remove the fuse, start the vehicle and move it back and forth a few feet and turn off the engine. Then you replace the fuse and now you have 4WD control again for a while. On my 2006 Jeep Grand Cherokee it is Fuse #25.

    The fact that many people are able to fix the problem with this fuse trick tells me that my circuit board is probably OK or the warning message would come back immediately. I expect that the software patch that looks for a problem may be responding to intermittent noise instead of a solid indication of failure. Perhaps even electrical spikes from starting the engine or cycling the AC compressor might give a spike that the FDCM counts a failure and then locks out the 4WD control.

    With this kind of control systems they should be able to add a little more logic to not only detect conditions that indicate there might be a problem, but also do some testing to be sure that the problem is solid and not an intermittent. For example something as simple as putting time delays on the inputs to make sure that the indication of a bad board stays for more than a second or two. Or add some subsequent testing to make sure that the problem exists a few minutes later. And if it doesn't, then reset the lockout.

    Jeep appears to be taking a big risk with the cheap fix. They admit to knowing they have a problem with a cracked circuit board. You dont fix a cracked circuit board with software. They should fix or replace the circuit boards. We buy these vehicles because we expect some kind of quality from Jeep. As the word spreads that Jeep has screwed up the most desirable feature and is willing to cripple the vehicles rather than provide a real fix the word will get out and they will suffer like GM was over the problem with their ignition keys.

    Instead they are in DENIAL that this problem exists. From internet postings it appears to have become a CASH COW for less than reputable service departments. They deny that they've heard ANY complaints from people having this problem and proceed to try to sell new actuators or other fixes. The follow up posts often tell how they pay hundreds of dollars for fixes and then the problem comes back. These are growing and may soon hit a critical mass that could be severely damaging to the Jeep reputation.

    And heaven forbid that someone is killed or injured because they get caught in an off road situation and cant get into 4WD low when they need it. Or someone who tows their Jeep behind an RV has to leave it in a bad location because it wont go into 4WD Low and has it stolen or damages while they drive their RV to some place to get help.

    Chrysler Jeep needs to take responsibility for this screwed up fix and do a real N23 fix. Even if they have to spend a lot of money on circuit board replacement labor, it may be well worth it to protect the brand.

    I'm at a different dealer now to have it checked. We'll see.

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