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Discussion Starter #1
Hello everyone,

So as the title says I have the dreaded 'Trans Fail Prog' error on my 2004 L322 4.4. I have read the many of the threads on the forum regarding this message and there has been some excellent help given. I think I have an idea what needs to be done to rectify the problem comparing my issue to others threads. I think it might be a problem with a split O-ring as explained by RRPhil back in 2015 https://www.rangerovers.net/forum/6-range-rover-mark-iii-l322/20824-transmission-fail-safe-program-slams-into-2.html however I would like a 2nd, 3rd, 4th........ opinion on this so let me explain what has been happening. During a long drive I suddenly got the 'Trans Fail Prog' error and the car went onto 4th gear and like a lot of other cars with these issues it went away when the car had been parked for a while. Initially I would get around 25 mins before the error would pop up on the dashboard and normally the error always came when i was slowing down and the transmission was coming down the gears now I only get 10 - 15 mins before the error shows. I checked for an error code and I saw it had a 'P0755 Shift Solenoid B' error. I contacted a local automatic transmission specialist and he said that it was probably better if i changed the solenoid and the wiring harness as the harness failing was a common issue on these transmissions so I agreed and paid him to change the solenoid, harness, filter and fluid. after the work had been done the problem is still present. The mechanic at the garage suggested that it might be the Transmission Control Module because I mentioned that I have sometimes received the error while stationary at the traffic lights and I wasn't putting any stress on the transmission. I bought a second hand TCM and swapped it with the one in the car and still the problem is there. In a nutshell i now get around 10 -15 minutes of normal operation before the error appears. Before the error appears the transmission work perfectly well, changes gear smoothly and all gears working. After the error appears the transmissions is locked in 4th gear, reverse still works although it makes a bit of a thud going from drive to reverse and back. At the weekend I did a little test and started the car on the driveway and just left it in 'Park' to see if the error would appear without driving and it did, after around 30 -35 mins i got the usual 'Ping' 'Trans Fail Prog' error and I hadn't moved the gear selector from 'P'.

Does this sound like it just needs the O-ring replacing or is it more? looking forward to any advice given by some of the ZF Transmission Jedi Masters that frequent this great forum.

Thanks

Stu
 

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During the first few minutes before the transmission goes into failsafe, what happens if you select neutral and try to select low range on the transfer box? Will it go into low range and then back into high again?

Phil
 

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Discussion Starter #5
During the first few minutes before the transmission goes into failsafe, what happens if you select neutral and try to select low range on the transfer box? Will it go into low range and then back into high again?

Phil
Tried it tonight after work and I was able to select low range and back to high range without any errors or warning sounds.
 

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I had the same issues for a while until I find out that the problem was a battery issue. When it is parked at night the air suspension and the cleanning air system uses the battery, in the morning you start it normal because it just went down on power a little bit once you are drive in it it take time to recover the charge and if you go hard in the gas pedal it drain the rest of the power that it need to operate in normal mode.
I am still having this issue and the way that i fix it temporary, is to charge the battery at night.
 

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Tried it tonight after work and I was able to select low range and back to high range without any errors or warning sounds.
I just wondered if the generic scanner was having difficulty interpreting the correct error code (which is Land Rover specific). One possibility was a duff signal from a faulty potentiometer in the transfer box shift motor but, if the transfer box is happy shifting between ranges, this seems unlikely. Is there any chance you could get the stored error codes read by a ‘proper’ Land Rover diagnostic machine to see if it still points the finger at shift solenoid 2?

Phil
 

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Discussion Starter #8
Hi Phil,

After the initial attempt at repairing the issue I returned to the place who carried out the repair and he took the car to another garage to have the codes read with what I was told was a machine that could read land rover codes. When I spoke to him later that day he said the same error came up for 'solenoid B' but didnt give me any codes. I will contact him tomorrow to confirm the error and to see if he has the code. If he doesnt have any codes looks like I might have to book in at Land Rover for a diagnostics session, god knows what that is going to cost :-(. I will let you know what i find out.

Thanks for your input Phil,

Stu
 

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Discussion Starter #9
Hi Phil,

Spoke to the garage who took it to check the error code. He said he doesn't have the code but it was saying the only transmission fault was 'shift solenoid B' (a few other codes but nothing to do with the transmission). Do you think I should get the code read by Land Rover?

Stu
 

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As you’ve already replaced the shift solenoid, the internal wiring harness and the ECU, it’s hard to imagine what else could be wrong with that particular circuit. I suppose the only remaining possibility is a continuity issue with the main transmission wiring harness (which is taped into the engine harness) but why a fault here would be temperature/time dependant I don’t know. The main transmission loom can be tested from the ECU end at the 40-pin C1835 connector with:


  • pin 26 at the ECU corresponding with pin 9 at the transmission’s 16-pin connector (green wire)
  • pin 21 at the ECU corresponding with pin 16 at the transmission’s 16-pin connector (yellow/blue wire)






I still believe that it’s worth trying to get the P0755 code validated by a ‘proper’ Land Rover diagnostics check.

Phil
 

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Discussion Starter #11
Hi Phil,

OK so its £150 for a diagnostics session at my local Land Rover dealer, not sure if that is just for a plug in and read the codes or some actual diagnosing the fault I am guessing it will just be a plug in and read the codes. A friend has told me about a garage in Oldham who can read Land Rover codes. In your opinion should I go to Land Rover or seek out an independent garage who can read the codes at a more reasonable cost? Regarding checking the pins is the transmission 16 pin connector easy to access?

Car update. Normally I jump on the motorway just after setting off for work and all is fine until I come off the motorway and start to come down the gears at which point we get the TFP error and locked into 4th. Today while still on the motorway the TFP error popped up and the transmission dropped down to 4th.

Stu
 

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You just need a place where they have diagnostics kit capable of reading Land Rover-specific transmission fault codes. £150 is obviously too high a price to pay just for validating the iCarsoft fault reading so I should go to an independent workshop, if I were you, where they’ll probably use Autologic or similar.

You can get at the 16-pin connector from underneath but access for testing the individual pins isn’t too great.









Phil
 

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Discussion Starter #13
I spoke to the garage who repaired my timing chain guides earlier in the year and they can read the Land Rover codes for me as well as check the pins you have mentioned. I know it's not possible to be 100% sure without stripping the transmission but at this point are you ruling out an A-clutch O-ring failure?

Stu
 

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If the A-clutch was slipping, then the transmission would failsafe to 5[SUP]th[/SUP] gear and not 4[SUP]th[/SUP]. You sound pretty sure that your transmission is selecting 4[SUP]th[/SUP] gear.

Another possible thing to try would be for me to lend you another valve body assembly to see if that makes any difference.



Phil
 

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Discussion Starter #15
Hi Phil,

I can test again to confirm 4th. Last time I tested I ran the car in manual mode so I could see which gear I was in and when it locked it locked into 4th. I will test again later today. I would love to test another valve body assembly to see if it makes any difference. Could you PM me some contact details.

Stu
 

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Discussion Starter #16
Confirmed the car is going into 4th gear when I get the 'Trans Fail Prog' error. I was driving the car in manual mode so I can see which gear is selected and as I was going up through the gears it jumped up to 4th and locked.

Stu
 

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Yes, so that doesn’t sound like the A-clutch O-ring issue. You just need to get the ‘Solenoid B error’ validated now. In particular, you need to be looking for any DTC which reads “noise on actuator signal” or similar. If the higher-end diagnostics kit still gives the same solenoid error then it might be worth swapping the complete valve body assembly. After that, it becomes more difficult as you’re involved in trying to trace an electrical/electronic fault.

Phil
 

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This is actually insane. You have literally described the problem I am currently having down to the exact detail. My 2003, with 205xxx KM works great for 10-15 minutes upon cold start, shifts smooth like butter, RPM' are normal and shifts are normal. My reverse also " thuds " about 2 seconds after shifting into reverse. Once the range rover has got to normal operating temperature the trans fail safe message appears on the dash ( usually 10-15 minutes into driving off a cold start ).

The past few days It didn't pop up, but after literally just going and driving the Range Rover around the block it decided to show it's ugly pixelated text.
 

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Discussion Starter #19
I feel you pain mate. I will keep this thread updated until I hopefully get the problem resolved. Hopefully the thread will help yourself and other people get to the bottom of some of their transmission issues. What is it with these cars? Its a definite love hate thing!
 

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This is actually insane. You have literally described the problem I am currently having down to the exact detail. My 2003, with 205xxx KM works great for 10-15 minutes upon cold start, shifts smooth like butter, RPM' are normal and shifts are normal. My reverse also " thuds " about 2 seconds after shifting into reverse. Once the range rover has got to normal operating temperature the trans fail safe message appears on the dash ( usually 10-15 minutes into driving off a cold start ).

The past few days It didn't pop up, but after literally just going and driving the Range Rover around the block it decided to show it's ugly pixelated text.
Over half of the 5HP24s that I re-manufacture have been removed from the vehicle because of precisely these symptoms, and it’s almost always the failed O-ring on the A-clutch causing this. The O-ring splits because the axial bearing between the B-clutch hub and the C-clutch drum has failed, allowing the A-clutch drum to slide within the B-clutch drum. The transmission will failsafe to 5[SUP]th[/SUP] gear if this is the cause.

Stufal69’s issue appears to be different because his transmission selects (the default) 4[SUP]th[/SUP] gear for limp home, not 5[SUP]th[/SUP], and the diagnostics is telling him it’s a solenoid fault.

The chances are that your fault is ‘the usual’ O-ring failure.

Phil
 
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