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2002-2005 Range Rover MkIII / L322
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126 Posts
Discussion Starter #1
Greetings,

I am reluctantly posting a new thread about my encounter with trans failsafe prog, but after having read countless threads on this forum including many that had solutions from some of the more senior and knowledgeable Rover folks here, I am at a loss for what is exactly happening to my 2004 Range Rover HSE l322.

My rover now has 99,000 miles, but about 5,000 miles ago (2 months ago), my wife and I were on the highway, moderate ambient temperatures (70s), trans failsafe prog. came on at about 70mph for the first time. Upon stopped, shutting off the engine, and restarting it, we could drive for 10-15 minutes before trans failsafe came on again. We have Storey Wilson's all-comms and saw in the software that the transmission was throwing an "output speed sensor short to ground" code. Over the next two months the trans failsafe was somewhat reproducible but became more erratic, up until 2 weeks ago, trans failsafe would erratically come on, then immediately go off (before actually going into Limp Home Mode), and flash on and off several times. Sometimes it will stick to trans. fail safe and enter LHM, other times it will flash but not enter LHM.

One some occasions, upon immediately starting the car, it will chime trans failsafe, stop it and start it and it may work perfectly. Sometimes we can drive it to work (10 minutes all highway) and not encounter a trans failsafe, other times we do.

Two days ago we were finally able to get the car on the lift, change the transmission fluid, filter, and transfer case fluid (we used the OEM Castrol stuff in the NV225) and Valvoline Maxlife ATF (spec is the same as Esso), did the proper fill procedure, everything still shifts fine...

Absolutely no changes.

I am aware of the STC4444 part and how to test it, and will likely remove, test, and possible replace the output speed sensor soon.
I am also aware of the transfer case shift motor causing issues. One thing I noticed, is when trying to switch from hi to low range, the car would not reliably shift to low range and in one case got stuck in low range and in one case got stuck in limbo where it was possible not in low range and not in high range and kept flashing "select neutral." This ONLY happened when I was playing with the low-range button.

So my question is this:

Based on the symptoms described above, what do you believe may be the most likely cause of my trans failsafe prog. issue? Am I looking at possibly multiple issues? Or could it be narrowed down to one of the following?

1. A clutch issue that Phil has identified and described so well on these forums
2. Faulty ZF5HP24 output speed sensor STC4444
3. Faulty/partially operable transfer case shift motor IGH500010


BTW: I am somewhat of an advanced DIYer and also own a BMW 8 series with a ZF4HP24, and have also done fluid changes and work on a BMW E83 X3, so these types of transmission configurations aren't new to me, but always keep surprising me! 8-0=

Thanks in advance.
 

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LEGACY VENDOR
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2,369 Posts
Your problem sounds electrical and the approach to tackling the transmission failsafe message should always be the same. The most likely cause is low battery voltage (do you measure 14V across the battery terminals at tickover?) followed by the transfer box shift motor potentiometer (can you successfully get into low range and then back to high?). Only once these two have been ruled out should you consider that it might be a transmission fault. The output speed sensor error is a red herring – you can ignore it.

In your case it sounds like the shift motor potentiometer is playing up so I would concentrate on that if I were you.

Phil

P.S. Just a word of advice – never put anything other than Mobil ATF LT71141/ZF Lifeguard Fluid 5/Pentosin ATF 1 in your 5HP24.

 

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Registered
2002-2005 Range Rover MkIII / L322
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126 Posts
Discussion Starter #3
Phil,

Thanks so much for your reply.

I wanted to provide an update. While I did give the battery a 100% charge with my CTEK, to confirm voltage was not the issue, I learned that the problem was indeed the transfer case shift motor, which was not reliably shifting between high and low. I removed and sent mine for rebuild through Cardone and upon re-installing the unit, the trans failsafe issue was completely gone. I haven't seen it come back again, and the shift motor is now very quickly and reliably shifting between high and low on-demand.

Bottom line is I didn't need to purchase a new $1600 shift motor, but had it rebuilt, costing me $350 through RockAuto and took about a week.

Thanks again.
 
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