What causes the ECU to go bad?
I have a 2007 Jeep Commander Limited 4.7L.
I bought it used a month ago. It was running rough when I test drove it. The dealer checked it out and said that it was the ECU. They replaced it and I drove it for two weeks. One night it would not start. I had it towed back to the dealer and the mechanic said that it was the ECU again. the coils were not getting the signal from the ECU. So they are waiting for a new one to replace it.
My question is ( which the mechanic couldn't answer ) what caused the ECU to fail?
If the coil outputs keep burning up, I'd look at the coils as the problem.
When ECU outputs fail, it's often the part that's connected to them that causes the failure.
For example, a shorted or failing coil can overload the driver circuits in the ECU and kill that section inside the ECU.
If the mechanic couldn't explain that, I'd seriously look for another dealership/shop.
And if the coil outputs are dead on the ECU, I'd have all the coil packs tested, and if you find any bad ones, I'd probably replace all of them at the same time. The "good" ones are the same age and aren't far behind.
If the coil outputs were the issue on the previous ECU, and the coil packs weren't checked before the "new" ECU was tossed in there, I'd expect the dealership to fix their oversight and replace the ECU (warranty or service policy, their choice), after they test all the coil packs
. I wouldn't expect them to pay for the replacement coil packs, but I would expect that they'd pay for the tow and do something (discount, courtesy car, whatever) for the inconvenience their incomplete diagnosis caused you.