ML 270 strange issue, won't change down gears.
Discussion
We've had two similar vehicles with this issue, one we never diagnosed before it suffered a total failure (likely unrelated to this issue), the other we've got now, however even after asking around we've not found anyone who appears to have had or know of this error.
We have an ML 270 03 Plate. After around 30-50 mins of driving the car will stop changing down gears. Remaining in 4-5th gear, with the revs capped and the car only able to do 70mph flat out (foot to the floor). If the car is brought to a stop and the engine turned off and then on again the system re-sets and it works as normal. However the error might reappear after 5-30 mins after that point again. Sometimes it reappears fast, sometimes it takes the 30mins or so.
One garage put it on their computer, but it wasn't logging any errors for them to diagnose.
It has recently had a full gearbox oil and filter change, which the garage thought might fix this issue, but no luck.
As a passenger in the car you can't tell its happened, the driver however very much can tell as they've lost all lower gear changing and have to have their foot to the floor to go at any speed.
If anyone has had any experience of similar or might be able to suggest what's going wrong we'd be most grateful to hear.
We have an ML 270 03 Plate. After around 30-50 mins of driving the car will stop changing down gears. Remaining in 4-5th gear, with the revs capped and the car only able to do 70mph flat out (foot to the floor). If the car is brought to a stop and the engine turned off and then on again the system re-sets and it works as normal. However the error might reappear after 5-30 mins after that point again. Sometimes it reappears fast, sometimes it takes the 30mins or so.
One garage put it on their computer, but it wasn't logging any errors for them to diagnose.
It has recently had a full gearbox oil and filter change, which the garage thought might fix this issue, but no luck.
As a passenger in the car you can't tell its happened, the driver however very much can tell as they've lost all lower gear changing and have to have their foot to the floor to go at any speed.
If anyone has had any experience of similar or might be able to suggest what's going wrong we'd be most grateful to hear.
We had a BMW before which was a long long list of repairs before we finally sold it. So I still end up thinking of "BMW" whenever it relates to car repairs My best advice would be to find a trusted Merc specialist or possibly (insert make of gearbox here) auto specialist.
It would be a good place to start with a full manufacturer level diagnostic and software update.
What you describe doesn't sound physical, more likely software/ecu.
With one possible exception, pick up in the gearbox causing temporary filter/pipework blockage, which is then cleared when it stops running, to find if this is the case would likely require a strip down of the 'box sump & checking the transmission cooler (if fitted) and its lines are clear.
It would be a good place to start with a full manufacturer level diagnostic and software update.
What you describe doesn't sound physical, more likely software/ecu.
With one possible exception, pick up in the gearbox causing temporary filter/pipework blockage, which is then cleared when it stops running, to find if this is the case would likely require a strip down of the 'box sump & checking the transmission cooler (if fitted) and its lines are clear.
Sounds like the transmission is going into limp mode. If it detects anything amiss it will limit it's self to the last known good gears to prevent further damage. If it's not logging any fault then you might have to read the codes whilst it's happening. Probably just a faulty sensor.
My thanks for the advice all.
Out of interest is there any viable way to read and log the codes whilst the car is being used and run around normally? Or is it really something that would just require a garage to put the car on a monitor and then run it on rollers until the error appeared.
Out of interest is there any viable way to read and log the codes whilst the car is being used and run around normally? Or is it really something that would just require a garage to put the car on a monitor and then run it on rollers until the error appeared.
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