Bought 1998 clk 320a and immediately lost power on freeway. Towing and dollars later at my home we eventually determined it was ecu. I Made the mistake of choosing ecutogo in florida home of johnny speed talker. They had me send to their "denver" office where it sat at a ups mailbox for a week until I tracked it for them.
A month later I received unit and it operated properly for 3 weeks then failed. ecutogo johnny couldn't tell me what the guy in denver repaired and in fact told me he was forced to take a leave of absence and was no longer available. he had me send it to florida office for repair but I was certain he didn't have a clue when we spoke a week late. They returned it untouched it appeared. during that time I did extensive search for cause with the car and found some bad wiring and improved the grounding points. The symptoms when the unit was returned were the same high fan immediately came on, key turned freely, all equipment and dash worked but no crank or fuel pump. when those relays were jumped each worked. i had purchased 2 other ecu's off ebay . I took a new one and swapped immobilizer chip from my original. the fan didn't engage, key turned freely, all accessories worked along with dash lights but still no crank or start. it would click if key was turned fast. Someone suggested improving ground which i did and the car seemed to start for 2 seconds and died then back to no crank/start. We worked on all ground connections with no success. I then put the original eeprom into the unit thinking this was the answer but now back to high fan immediately, key turns freely no crank and no start. You can still work both starter and fuel injectors by bridging relays. It's got to be some type of immobilizer issue but am I correct it's not the key transponder ring nightmare because key turns? It also makes a beeping sound when inserted. Could it be the transmission problem I've read about? The shift linkage works properly and there is no display of gears on dash like newer ones. I have already replaced the brake switch. I can't find a fan servicing the ecu or a fuse for one. I installed my own fan. If you swap the immobilizer chip which is suppose to contain the cars vin number what else is necessary to use a new ecu. What is flashing? How do I know if the original chips are good. I need a quick complete tutorial as to my best least costly options are to fix it. I am retired disabled and not able to take the car to MB shop. Thank you very much

 

Sorry
I am sure my posting seemed more like a rant. It is easily my most frustrated automotive experience in my 64 years

I am asking if there is a way to fix the problem myself rather than spending a lot more money?