Re DEF fluid quality. We have had the 160 for a little over a year and 20,000 miles. Besides the transmission replacement and the inframe rebuild we had numerous water in fuel lights and full water separators last winter. This resulted in a half a dozen trips to the dealer and lots of head scratching and draining/sealing of the fuel system. The tech sent a sample of the DEF from the tank for testing to see if that was part of the issue. It was not. The problem did not occur this winter on this truck so whatever the dealer did, on one of those many service visits has resolved that problem. The check engine light this weekend turned out to be a plugged crankcase vent valve. It has eaten a half a gallon of coolant since the inframe a couple of months ago however. No indication of a cooling system leak and oil is not milky. That one is on "watch". This truck has been to the dealer 13 times for problems since delivery.
I think everyone involved thinks there are two different generic issues with the new fusos. First is the transmissions, which are all being replaced if they fit in a range of serial numbers. The second is the multiplex wiring and problems associated with moisture. Re the fault codes on the 125. The last time this happened was about a month ago in heavy rain. From memory got check engine yellow light, then red light and tone. Engine de rated. Stopped for fuel and started and stopped engine to see if that would clear, did not. Decided to head back to dealer, a drive of about 30 miles. After about 10 miles all warning lights went off, tone stopped and engine went back to normal power. Briefly contemplated completing the run but since it was 150 miles each way I kept going back to the dealer. In 10 more miles the original warning indications all returned. I was sitting at the dealer when the tech walked in to begin work at 7. By noon he called and said they had finally been able to clear the codes. The system would allow codes to be read but not cleared until the truck dried out enough in their shop. They did get multiple codes off the truck. This truck has 7000 miles and over half a dozed trips to the dealer. Regarding the dealer they are the go to shop for medium/heavy trucks around here. They have an outstanding reputation but the new Fusos are something different. Everybody, including Fuso, is learning on the fly with these things. The tech that specializes in Fusos is a very competent guy but at a loss and just keeps trying things. The help line is not much help as they don't know either. I have been told daimler is involved with the DEF/DPF/moisture issues and is working with mitsu to resolve. It's going to be pretty dry here for six months so I don't have to worry too much until fall. By then maybe they will have it resolved. I'm hoping the transmission problem is a reflash to get the computer to make quicker decisions around gear selection and throttle position. Thats the problem that is dangerous not inconvenient.
By way of comparison I have a 2012 Ford F550 6.7 that does similar duty to the 160. In the 30,000 miles on that truck it has been back to the dealer for oil changes. Nothing more.