hi guys I got the Trans fail safe warning message ping up today along with the car locking to 4th gear (can't change gears manually either). I managed to limp the car home and hooked my icarsoft scanner up which is throwing the following faults:

P0755 State: Plausability Fault. Shift Solenoid B
11 State: None. Shift solenoid 2 Fault

Does anyone have any idea on what the cause of this fault code is and how to go about fixing it, thanks in advance for any help 2004 Range Rover Vogue 4.4 v8 LPG, Java Black, 22' Hawke Alloys, Black Beast

If RRPhil is about then he would certainly know.

I don’t know how much you know about your ZF5HP24 transmission so apologies if this obvious but you have shift solenoids in your transmission that without refreshing my memory are accessible without removing the transmission but you would need to to drop the transmission sump. I recall Phil saying you can swap solenoids around as you have a few, possibly 5 and some are interchangeable to test them to see if the fault moves with the solenoid.

If you were going to remove the sump and oil you could do an oil and filter change st the same time but only use a genuine filter and the correct oil is an absolute must.

HOWEVER - before doing anything I would google RRPhil and shift solenoid and see what comes back as it is expensive changing the oil and I wouldn’t want to lead you down a path that could be a more simple wiring issue or something else.
Does the fault clear with the icarsoft ?
If you don’t know much about the transmission , have you got the Rave manual ?

Thanks for your reply holiday chicken, hopefully RRPhil sees this message as he is the man when it comes to transmissions for sure.

The icarsoft removed the error code and I was able to drive the car for about 10 miles before I got the trans fail message again, it drove fine for those 10 miles with smooth gear changes and nothing out of the ordinary. I agree with what you're saying regarding it would be an expensive strategy to just swap solenoid around to see if one was at fault due to the high cost of the transmission oil.

I'm thinking I should just bite the bullet and get the solenoid replaced at the same time as doing a gearbox oil and filter change as that wouldn't add too much to the labour cost. The big question is where do I buy the correct solenoid B for my gearbox and how difficult is it to change it over? The car is now on 168k miles and I've had it nearly 5 years so it's due a oil and filter change anyway (the gearbox and/or oil and filter were changed by a previous owner between 80 - 120k according to the garage that used to look after the car for her) 2004 Range Rover Vogue 4.4 v8 LPG, Java Black, 22' Hawke Alloys, Black Beast

I have replied to your other thread as well, JPAT for spares but I would send Phil a message as he will definitely be able to advise you better than me and he may also have the spares you need on the shelf

https://www.jpat.co.uk/uploads/1/0/3/5/103..._5hp24.pdf

This is the correct fluid

https://www.ebay.co.uk/itm/Mobil-ATF-LT-71...1244234762

Filter needs to be Filtrans genuine ideally

https://www.island-4x4.co.uk/gearbox-filte...26665.html

Thanks for the info holiday chicken, do you have contact details for RRPhil or the best way for me to get hold of him? 2004 Range Rover Vogue 4.4 v8 LPG, Java Black, 22' Hawke Alloys, Black Beast

Problems with the shift solenoids are extremely unusual for the 5HP24 so, if that is the problem, you’ve been very unlucky. I can certainly send you a ‘used but fully tested’ replacement to try. If it fixes the issue, it’s yours for a tenner. If it doesn’t, you can just send it me back. It’s possible that the internal wiring loom is causing the issue rather than the solenoid - unfortunately, the controller isn’t clever enough to be able to distinguish between the two. If you’d prefer you can send me your 'faulty' solenoid and I’ll test it for you (no charge).

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You are a gentleman Phil, i'll be leaving this one with you.

Thanks for your reply Phil and I appreciate your kind offer regarded trying the solenoid. Is there a way I can trouble shoot the exact cause of the fault (wiring or solenoid) at home without taking the gearbox sump off? I have a multimeter so I could in theory try and check voltages and report back if you could tell me how and where I need to check?

Also is the solenoid inside the gearbox or is it on the outside where it is accessible without removing the gearbox oil sump? Sorry for the newbie question but I don't have much knowledge of gearboxes (had the old girl nearly 5 years and this is the first time I've had a Trans Fail Safe error!)

Also if I clear the error code I'm able to drive the car for 15 minutes as normal before the fault recurs - would driving the car like this when the fault code is cleared be causing any damage to the gearbox or is it ok to drive by clearing the fault? 2004 Range Rover Vogue 4.4 v8 LPG, Java Black, 22' Hawke Alloys, Black Beast

The solenoids are part of the valve body assembly, which is inside the sump. The only test you can do externally is to measure the resistance between pins 9 & 16 at the 16-pin connector on the back of the transmission. For a shift solenoid the resistance should be around 27 Ohms. This would tell you if there’s a short or an open circuit but, as previously mentioned, it doesn’t tell you whether the fault lies with the internal wiring loom or the solenoid itself. Also, it doesn’t help identifying the temperature-dependency of your fault.

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Thanks for the update Phil, I'm thinking the best option here is to replace both the solenoid and the internal wiring loom - I appreciate that the solenoid may not be at fault but i figure it makes sense to replace it anyway whilst the sump is off. I'll send you the removed solenoid which you can have free of charge if it works. Do you know where I can get the wiring loom from or the part number for it? Is replacing the wiring loom a straight forward process with the sump off off?

I'll remove the fault code now and take the car for another test drive to see if the fault recurs after a similar amount of time/miles or if it's more unpredictable (which I guess would lean more towards a wiring issue). I'll update once I'm back from the drive 2004 Range Rover Vogue 4.4 v8 LPG, Java Black, 22' Hawke Alloys, Black Beast

Both the harness and solenoid are available from Land Rover (part numbers YMD001500 and LNN000030 respectively) but they’d be wanting over £300 off you, for the privilege. The parts would be cheaper from a ZF parts specialist (ZF part numbers 1058 227 019 and 0750 132 122) but, to be honest, I’d want to be pretty sure exactly where the problem lay before I spent that much money.

Replacement of the harness/loom and solenoid are covered in RAVE (44.15.52 & 44.15.45)

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Yes Phil I agree that is a lot of money to pay without knowing the exact fault. I've just returned home after clearing the fault codes and going for a test drive, the results/observations are as follows:

1. The car drove fine for approx 20 minutes/20 miles before the same solenoid B fault code appeared.
2. I stopped the car, switched engine off, cleared the code and attempted to drive but the fault would not clear and the car would only drive in 4th gear (there was also a noticeable clunk sound when putting the Gearbox into drive from park)
3. I was able to use manual mode and the gear display number changed through the different gears but there was no actual gear change and it stayed in 4th
4. I was able to change from high range to low range mode, when pulling off in low range again a noticeable thump/clunk was felt
5. The clunk sound was also evident when selecting reverse

I will leave the car overnight and at some point tomorrow see if the error code clears and let's me drive as normal again with a completely cold gearbox, at the moment it seems like the code clears when the car is cold but not when it's warm although that could just be a coincidence. Based on the above what are your thoughts - does this seem more like a physical solenoid issue or a electrical wiring issue? 2004 Range Rover Vogue 4.4 v8 LPG, Java Black, 22' Hawke Alloys, Black Beast

To be honest, I keep thinking of two things:

1. Shift solenoid faults with the 5HP24 are extremely unusual
2. By far the most common fault with the 5HP24 transmission is the failed B/C clutch axial bearing, which produces exactly the symptoms that you have described

However, as your diagnostic kit seems to be adamant that there’s a shift solenoid/wiring harness fault, that still seems to be the obvious way to proceed.

How certain are you that 4th gear is being engaged in failsafe mode and not 5th gear?

Phil

I'm pretty certain it's locking into 4th gear as on 2 of the occasions when the fault code appeared I was driving the car in manual mode and both those times gear 4 showed on the dashboard display. The engine revs at various speeds also correlated to being in 4th gear (I drove home at approx 35mph and the car 'felt' like it was in 4th). On my icarsoft scanner it shows the drive mode as 'Limp Mode' when the fault occurs, not sure if that has any significance?

If the fault was the B/C bearing fault what fault code would you expect to be thrown up? That sounds like a much bigger and painful fault so here's hoping it's the solenoid! What's the significance of the gear it's locking into - would it only lock into 5th gear if it was a B/C bearing fault or can it still lock to 4th with that fault?

I'm using the icarsoft LR v1.0 diagnostic kit with the latest updates, cracking bit of kit with lots of live data highly recommended. 2004 Range Rover Vogue 4.4 v8 LPG, Java Black, 22' Hawke Alloys, Black Beast

Last edited by Knightrider on 29th Oct 2018 4:50am. Edited 1 time in total

Phil I was up late so I decided I'd go for another test drive to try and get definitive answers regarding the actual gear it locks into etc, I made the following observations:

1. With the gearbox cold I was able to successfully clear the fault code and drive normally.
2. The fault code came up sooner on this test drive, I would say approx 10-12 minutes of driving. The fault code state seems to vary between plausibility error and open circuit, always for Solenoid B.
3. The gearbox is 100% locking into 4th gear - this is confirmed by checking the rev counter at 50mph. The icarsoft also displayed the gear as 4th as well as the manual mode display on the dash
4. The gearbox oil temperature at the time of the fault was 85 degrees Celsius
5. All 3 solenoids went to the OFF position when the gearbox locked into 4th (in normal operation 4th gear should have solenoid B ON and the other 2 shift solenoids OFF. 2004 Range Rover Vogue 4.4 v8 LPG, Java Black, 22' Hawke Alloys, Black Beast