Yes, if the OVP is faulty, no power to the ECU, but the engine will operate.

Mercedes claimed that the KE system will function even if the electronics fail. That's true, but they neglected to state that all the cold start enhancements are in the electronics, so if the ECU is inoperative the car will be hard to cold start.

Remove the big ECU connector and carefully check it for bent pins/receptacles, corrosion etc. If it checks out give both the pins and receptacles a shot of electrical contact cleaner, reinstall carefully and securely and see if that helps.

If any KE ECU failures have been reported here, they must be rare, but connector problems on 25 year old cars are common.

Duke