'97 C230, @ 144K miles, threw CE light & went into limp-home mode, without warning... used primarily on the interstate, vehicle was asymptomatic before hand.

Dealer advised transmission had failed and a remanufactured unit would be required. Transmission oil and filter had never been changed.

Removed vehicle from dealer and checked fault codes:

ME.2
P0715 - read ETC DTC memory
P0720 - read ETC DTC memory

ETC.6
013 - speed sensor n3 (Y3/611)
109 - occasionally speed sensor n3 (Y3/611)

Found fluid in AT wiring harness plug adapter; installed new style adapter (140 270 02 50). Renewed fluid and filter, installed pan magnet. Drained fluid, although discolored, was free of metallic debris; some fine grey-colored particles were present in pan.

Now, 4,500 miles later limp-home mode has recurred, along with the same DTCs. Vehicle runs and shifts flawlessly, however, when codes are cleared. The interior of the new wiring harness plug adapter is dry.

The speed sensor in question is integral with the electric valve control unit (electro-hydraulic control unit; 140 270 05 61). A new unit is devoid of the six solenoid valves, however; installation requires transfer of the existing valves to the new unit.

A reman'ed valve body (140 270 06 06 88), although several $100 more, comes with a new electric valve control unit and solenoid valves.


Given the vehicle's mileage, would it better to install a reman'ed valve body, or would renewal of the electric valve control unit be sufficient to correct the speed sensor problem?