2000 S500
I'm having the following problems:
1. Hard shift between 3rd and 4th gear and when I get on the freeway and try to accelerate it hesitates to gain speed in this gear.
2. When braking to slow down there is a jerk between down shifts.
3. "Check engine" light is on and I already had the O2 sensors replaced costing $558!!!

I did a little research on this forum and one other person had all these same problems at once and he was recommended to have Transmission sensor and wheel speed sensor checked. I haven't had these checked but I wanted to confirm this is the problem so I don't get robbed and what it would cost approximately to replace these parts.

Thanks...

 

Hello, it could be many differnt thing but check trans fluid level first, you could have a dirty speed sensor on the conductor plate in the transmission, they get fine metal particles on them and it can cause the check engine light to come on and erratic shifting.

 

Hi,

Could be many things BUT I suspect the key to this problem is the fact that the CEL Check Engine Light is ON.

The Eng and Trans are linked by computer and engine problems are often reflected in gear change quality etc.

Of course I'm not ruling out a trans issue, low fluid etc. BUT I would start with the engine.

First step determine why the CEL is ON.

To establish this preferably your MB dealer (or good garage) will read the engine OBD (On Board Diagnostic) codes and this will point in the direction of the problem.
This is a chargeable job unless you have some goodwill at your MB dealership...BUT this is a job which should not be missed.
However don't give the garage the authority to repair until you have the results IN WRITING as a report/printout.

In addition the S Class has a "Flash" memory facility which gives the conditions under which the CEL was initiated. I'll lay odds it was during a moderate to heavy acceleration.
Ensure this data is recorded BEFORE the CEL is reset.

I suspect you will find that the O2 sensor change MAY NOT have been required and in fact the reason for that potential incorrect diagnosis was that the MAF (Mass AirFlow Meter) is nearing the end of its life and gives a very similar failure signature.

The MAF is quite expensive although a very simple DIY job to change. Search this forum (especially underSLK) since the MAF can sometimes be recovered by cleaning.

The other bit of diagnostic data that would confirm that it is the MAF is the LTFT (Long Term Fuel Trim) reading also available from the engine computer using the correct equipment.

If you get the garage to get this OBD data and post it I will confirm the diagnosis before you proceed further.

Stuart.