Mercedes ML Hybrid Transmission Issue

I've seen similar issues, though not on a Mercedes ML hybrid. Your symptoms point to electronic issues within the automatic gearbox, and the error code confirms it. Before replacing the transmission unit, check the wiring harness and connectors. A loose connection or corroded wire can seem like a defective unit. Also, check the transmission fluid level and condition. Low or contaminated fluid can cause erratic shifting and slippage, potentially triggering the error code. I remember a fluid change resolving similar transmission problems on an older vehicle, but with your electronic issues, it's less likely. What error code did the automotive ECU produce?

The automotive ECU error code was P0702, indicating an electrical fault within the transmission control system. I haven't checked the wiring harness and connectors yet, but I will. Given the electrical fault, would a fluid change fix it, or does the P0702 code mean a more substantial electronic problem?

Given the P0702 error code, and that it's an electrical fault, a fluid change is unlikely to resolve it. The error code suggests a deeper problem within the transmission control system itself, or the wiring. Checking the wiring harness is a good idea and something you can do, but P0702 often means the control unit is faulty. Considering your Mercedes is a hybrid, I'd advise seeking professional transmission diagnosis from a qualified workshop with experience in automotive ECU repair, before doing too much yourself. These systems can be complex.

I took your advice and went to a workshop specializing in Mercedes vehicles. Their diagnosis confirmed a defective transmission control unit. The unit was replaced, and the system recoded. The total cost was 1000€. The vehicle now operates as intended, with all transmission functions restored. Thanks for your help.