Hi, Paul here. Been lurking in the forums for awhile but have not really posted much. Wondering if you guys can help me with my problem.

I'm driving a 1997 Mercedes Benz E300D. About a month ago, my car suddenly went into limp mode - shifting is stuck in 1st gear, has reverse though. It doesn't shift in manual transmission mode as well 1-2-3-4. I didn't crash, spill anything on the consoles, drove fast over a hump or anything. I tried having my car read by 2 mechanics just to have a 2 opinions on the problem.

Device: Data Scan CPTronic Diagnosis HH@ / HH-II Model
Trouble Code: P0700 Refer to Read Transmission Control System Fault Memory

Device: Mercedes Benz Diagnostic Multiplexer Part No. 6511 1001 99 connected to a laptop
Trouble Code: P0702 - Read ETC Fault Memory


Here's what we have done so far in chronological order:

1. Changed Transmission Oil, transmission filter, oil pan gasket, steering oil. Checked if there was oil on the connector of the Transmission Control Unit (TCU) and there was none.
2. Changed the electic plate (the one found between the valve body and the 6 solenoids) since we saw that there's a thin line in the surface of the speed sensor and it might be cracked. Old solenoids were used.
3. This was the time I had my car scanned using the 2 devices mentioned above since the mechanic and I decided that we can't keep changing parts and it might be best to have my car scanned/diagnosed first.

4. Error code P0702 in the STAr Diagnosis indicated that"
Possible Cause - Fault in ETC control unit
Remedy/Test Step - Lines, connectors of N15/3 control unit

5. We then printed out the wiring diagram of the automatic transmission (AT) 722.6 and checked each of the lines. We checked the wires from the TCU to the passenger foot side, TCU to the fuse box, fuse box to the gear box area, etc. No wire was broken. Still no go, car still does not shift.


All is pointing to the Transmission Control Unit (that's what my mechanic say) and my logic seems to tell me that too. But before I pull the trigger on buying one, I just wanted to ask you guys what your opinions are. The TCU costs around USD 1,800 in my place (I live in the Philippines). Buying it is already a bit heavy but what I'm really afraid of is that the TCU is not the problem. I can't refund/return the part since the dealer here still has to import it from another country. Apparently, E300D model is quite rare here and he does not want to stock up on the part. What do you guys think? Are there other possible causes? Did we miss anything? Should I already buy the part? I can also buy the TCU online from the US or Canada and have it sent to my sister but somehow, I couldn't fint the part online. Where's a good place to buy if ever? Thanks in advanced for any help! And have a Happy holidays as well!

Mercedes Benz TCM Part No. 021 545 02 32 EGS (SIEMENS Brand)

By the way, we actually put in a TCU unit the mechanic had (different part number though) and the check engine light was gone. BUT it still did not shift.

 

The trans control unit is going to be vin and engine specific. There is a tsb for the earlier 722.6 transmissions in 210 chasis vehicles which states the valve body must be replaced with trans control unit. Try to find the info because it has part numbers listed on it.