SM3 Transmission Problems

My 2003 Renault SM3 (gasoline engine) has transmission issues: unresponsive paddle shifters, slipping gearbox, unclean shifts, and grinding noises. It's in emergency mode with an error code. Suspect a defective transmission control unit. Anyone else experienced this?

4 comment(s)

TCU gremlins! Similar experience with my SM3, though no grinding noises. Slipping and emergency mode sound familiar. Felt like the car couldn't decide what gear to be in. Paddle shifters useless. Check the wiring harness for damage or corrosion? Could be a connection issue, but sounds like the control unit itself. Any event that may have triggered the fault?

Thanks! I checked the wiring harness, no visible damage. Disconnected the battery. No specific triggers, just normal driving. Can you elaborate on your experience with the transmission control unit? Did replacing it fix the issue completely?

Replacing the TCU was the only solution for me. Like a switch flipped. Before, undriveable, constantly in limp mode. Afterwards? Smooth as butter. The garage said these TCUs fail for no reason. Check the error codes and wiring diagrams if you can before replacing it. Take it to a workshop for a look.

Thanks! Based on your experience, I'm convinced it's the transmission control unit. I'll arrange for its replacement at a workshop and provide the wiring diagram. The estimated cost is 1000€, but hopefully, it will restore my SM3.

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