E300td auto trans erratic operation

[johnsco]

It seems like it's the season for auto-trans problems.
After many miles of faultless service my 1998 E300TD is now sticking in various ratios ... Usually when warmed up ... sometimes it's 2nd.
Most often it appears to be 3rd.
Once it's started, it won't change out of this.
Putting the selector into P or N makes no difference.
When it's back in D, the same problem immediately returns.
Switching off and then re-starting sometimes cures it for a short time, but it's soon back.

A couple of things I've noticed.
Reverse still selects OK.
When this condition has occurred, the cruise still works.
However, the speed limiter does not.
Attempting to set the speed limiter gets a set of horizontal lines where the set-speed should be and some bleeps on the warning system.

Is there a speed sensor on the output drive of these 5 speed boxes that the limiter uses ?
Could this be a clue ?

Help please buddies.
I hope it's fixable, as the rest of the car is in reasonable condition for its years and the hard-work it does for me.

Thanks in advance.
J.

 

[Dieselman]

The ECU uses the ABS rings for speed recognition, but has speed sensors in the gearbox as well to check for slippage.

You will need the codes read, but I suspect the electronic plate or a wheel reluctor ring.

 

[johnsco]

Thanks DM.
I will get the codes read as soon as I can.
If it was the abs ring I would expect some abs or engine-management-related lights on the panel.
The cruise-controller and the engine-management certainly works off the signals from the abs rings, although the speed limiter appears not to.
I noticed this over the winter when I fitted snow tyres on the rear which were a tad larger in diameter than the ordinary continentals on the front.
The cruise would no-longer work - But the speed limiter would.

This is different.
The cruise still works, but the limiter throws up an error indication.

As you advise, I'll get the codes read.
Thanks for your help.

 

[johnsco]

Codes were scanned this morning.
As DM correctly predicted - It was the speed sensor.

As my old Works Engineer used to say:
"Disasters are much worse than that ... That sounds distinctly-repairable.

Thanks DM for your sound advice.