Mercedes ML gearbox problems
Discussion
Over the last few months the gearbox on my trusty old ML320 has become troublesome-locking itself in 1st gear or 4th gear every once in a while.Ive gone down the usual diagnostic route and some research on the internet has resulted in us rewiring the pilot bush-didnt work,replacing the valve block-didnt work,and most recently replacing the gearbox ecu-didnt work(about a grand spent so far-the whole car is only worth slightly more!)
Everything has been fine for the last month/1000 miles but coming home tonight the gearbox once again locked itself in 4th gear,and then when I was stopped at traffic lights I slipped the lever into Park,then into Drive,and it locked itself in first gear.Before we rewired the pilot bush and replaced the valve block it always had to be reset on STAR to work normally,but since this has been done then simply turning the ignition off then restarting clears the fault.Sometimes it logs a voltage fault,sometimes no faults are stored.
A local gearbox specialist suggested the problem may be related to the MAF sensor but the engine runs fine.
Its driving me mad now.Has anyone else had similar?
Everything has been fine for the last month/1000 miles but coming home tonight the gearbox once again locked itself in 4th gear,and then when I was stopped at traffic lights I slipped the lever into Park,then into Drive,and it locked itself in first gear.Before we rewired the pilot bush and replaced the valve block it always had to be reset on STAR to work normally,but since this has been done then simply turning the ignition off then restarting clears the fault.Sometimes it logs a voltage fault,sometimes no faults are stored.
A local gearbox specialist suggested the problem may be related to the MAF sensor but the engine runs fine.
Its driving me mad now.Has anyone else had similar?
you say the pilot bush was replaced. I assume this was done due to transmission oil leaking from it. Can you be 100% sure when this was done that no oil entered the main electrical wiring loom & then worked its way up into the ETC transmission control module which is located under the dash up behind the parking brake pedal. If you manage to find it there will be to large connector plugs & when removed there will hopefully be no trace of oil over the ETC control module terminals. If there is then oil has entered the control module & possibly shorted out the control module.
Its only a thought & worth checking. It does sound like its an electrical fault as it resets itself when you switch of & back on.
Its only a thought & worth checking. It does sound like its an electrical fault as it resets itself when you switch of & back on.
mbtech01 said:
you say the pilot bush was replaced. I assume this was done due to transmission oil leaking from it. Can you be 100% sure when this was done that no oil entered the main electrical wiring loom & then worked its way up into the ETC transmission control module which is located under the dash up behind the parking brake pedal. If you manage to find it there will be to large connector plugs & when removed there will hopefully be no trace of oil over the ETC control module terminals. If there is then oil has entered the control module & possibly shorted out the control module.
Its only a thought & worth checking. It does sound like its an electrical fault as it resets itself when you switch of & back on.
Thanks for the reply.Its only a thought & worth checking. It does sound like its an electrical fault as it resets itself when you switch of & back on.
The pilot bush was rewired as a stab in the dark as the most probable cause of the problem.There was no oil leaking onto it or working its was up the loom.When this didnt fix it we then replaced the valve block electro pack,which didnt work so we then replaced the circuit board within the gearbox.
My garage have inspected both the connection to the gearbox and also the ECU that you suggested in your post and there is no oil there whatsoever.They have also played with the wires to see if there is a possible break but there is not.A fault code was stored Code 106 which I believe relates to voltage.My guys also tested the alternator and found that it is a little down on the charge it should be producing but still okay.
MarsellusWallace said:
Over the last few months the gearbox on my trusty old ML320 has become troublesome-locking itself in 1st gear or 4th gear every once in a while.Ive gone down the usual diagnostic route and some research on the internet has resulted in us rewiring the pilot bush-didnt work,replacing the valve block-didnt work,and most recently replacing the gearbox ecu-didnt work(about a grand spent so far-the whole car is only worth slightly more!)
Everything has been fine for the last month/1000 miles but coming home tonight the gearbox once again locked itself in 4th gear,and then when I was stopped at traffic lights I slipped the lever into Park,then into Drive,and it locked itself in first gear.Before we rewired the pilot bush and replaced the valve block it always had to be reset on STAR to work normally,but since this has been done then simply turning the ignition off then restarting clears the fault.Sometimes it logs a voltage fault,sometimes no faults are stored.
A local gearbox specialist suggested the problem may be related to the MAF sensor but the engine runs fine.
Its driving me mad now.Has anyone else had similar?
It might seem like a statement of the obvious, but I take it you have done a fluid and micronic filter change to the 'box?Everything has been fine for the last month/1000 miles but coming home tonight the gearbox once again locked itself in 4th gear,and then when I was stopped at traffic lights I slipped the lever into Park,then into Drive,and it locked itself in first gear.Before we rewired the pilot bush and replaced the valve block it always had to be reset on STAR to work normally,but since this has been done then simply turning the ignition off then restarting clears the fault.Sometimes it logs a voltage fault,sometimes no faults are stored.
A local gearbox specialist suggested the problem may be related to the MAF sensor but the engine runs fine.
Its driving me mad now.Has anyone else had similar?
I have done three of these in the past few months; one of them was brought in on the back of a recovery vehicle. This cured every single one!
J
jith said:
It might seem like a statement of the obvious, but I take it you have done a fluid and micronic filter change to the 'box?
I have done three of these in the past few months; one of them was brought in on the back of a recovery vehicle. This cured every single one!
J
When we first had problems with the gearbox my guys did a gearbox oil level check as they were aware that a low level could make the car go into safe mode.They had a look at the oil and said it was still nice and clean and didnt need changing.If I recall correctly they said that it would smell of almonds if the oil was in need of a change.I have done three of these in the past few months; one of them was brought in on the back of a recovery vehicle. This cured every single one!
J
As the car resets the safe mode every time you start up it would seem that the problem is voltage related.Could old oil cause a voltage related problem?
I may be completely off track, but this fellow had the same problem on an E class and solved it I think.
http://www.mbclub.co.uk/forums/engine/130749-auto-...
http://www.mbclub.co.uk/forums/engine/130749-auto-...
ModMan said:
I may be completely off track, but this fellow had the same problem on an E class and solved it I think.
http://www.mbclub.co.uk/forums/engine/130749-auto-...
Yes I think the circuit board in the gearbox was replaced on that e class-which we did on my ml but it has not solved the problem.http://www.mbclub.co.uk/forums/engine/130749-auto-...
MarsellusWallace said:
jith said:
It might seem like a statement of the obvious, but I take it you have done a fluid and micronic filter change to the 'box?
I have done three of these in the past few months; one of them was brought in on the back of a recovery vehicle. This cured every single one!
J
When we first had problems with the gearbox my guys did a gearbox oil level check as they were aware that a low level could make the car go into safe mode.They had a look at the oil and said it was still nice and clean and didnt need changing.If I recall correctly they said that it would smell of almonds if the oil was in need of a change.I have done three of these in the past few months; one of them was brought in on the back of a recovery vehicle. This cured every single one!
J
As the car resets the safe mode every time you start up it would seem that the problem is voltage related.Could old oil cause a voltage related problem?
Yet another Merc in with change up and dropping out problems. A 230 CLK. It came in for a major service and MOT prep, running like a pig and spat out no less than 12 fault codes!!
After a monster service including transmission filters I manage to get it running sweetly with only one remaining code that related to the brake light switch. Now this is not just a switch that puts the brake lights on. It also sends a signal up the CAN bus that is integrated into the ABS and traction control via the gearbox.
New switch from Mercedes at an outrageous 8 quid and the car is perfect! I think you should try a fluid and filter change and a new switch. You've nothing to lose.
By the way, the reason for the voltage problem is that the ECU has to recognise hydraulic and mechanical actions it is programmed for as the box changes up and down. If you have a hydraulic problem caused by contaminated fluid; or even the wrong fluid, ('coz people buy the cheap stuff to save a few bob), then it upsets the signals to the ECU and flags up rogue codes scrambling the whole system.
Last month I had a 4 year old S Class in that was absolutely lethal to drive and flagged up no less than 15 codes!! All that was wrong was 1 faulty ABS wheel sensor; but it threw the whole system into chaos.
Let us know how you get on.
J
Thanks for the hints and tips J.
I suppose the problem is that the car runs sweetly and 98% of the time there is no problem with the gearbox-it just goes into safe mode once every blue moon,and when you switch the ignition off and fire it up again its fine.
Somebody has suggested today that the problem could be in the automatic gear selector and thinking about it the last time it went into safe mode and locked itself in 4th gear I put the car into Park then back into Drive before resetting and when I did this the car locked itself in 1st gear ??? He suggested there could be crap in the contacts of the gear selector and this could be causing the problem.
I suppose the problem is that the car runs sweetly and 98% of the time there is no problem with the gearbox-it just goes into safe mode once every blue moon,and when you switch the ignition off and fire it up again its fine.
Somebody has suggested today that the problem could be in the automatic gear selector and thinking about it the last time it went into safe mode and locked itself in 4th gear I put the car into Park then back into Drive before resetting and when I did this the car locked itself in 1st gear ??? He suggested there could be crap in the contacts of the gear selector and this could be causing the problem.
I had a similair issue with my AMG gearbox. The history stated that the gearbox had been serviced at the correct interval but I had given the car to a 20 yr long friend who owns a MB specialist.
He suggested a gearbox service after having witnessed Stealers 'servicing' a gearbox by simply draining it and re-filling it it may need to be serviced 'properly'.
When he dropped it to drain, clean and re-fill the gearbox he discovered that the stealer monkeys had not replaced a magnet back into the gearbox after cleaning it
. The magnet collects all the swarf floating around in the gearbox and prevents it from landing back onto the electrical connects in the pack. This may be happening with yours as the swarf shorts the box, trips the safe mode and then when you re-start the car, presto, the fault is stored but not current and the box runs fine again.
May be worth a check if it reappears.
M
He suggested a gearbox service after having witnessed Stealers 'servicing' a gearbox by simply draining it and re-filling it it may need to be serviced 'properly'.
When he dropped it to drain, clean and re-fill the gearbox he discovered that the stealer monkeys had not replaced a magnet back into the gearbox after cleaning it
. The magnet collects all the swarf floating around in the gearbox and prevents it from landing back onto the electrical connects in the pack. This may be happening with yours as the swarf shorts the box, trips the safe mode and then when you re-start the car, presto, the fault is stored but not current and the box runs fine again.May be worth a check if it reappears.
M
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