I added about 18" of wire and used butt connectors. I have to keep an open mind as I assume I found the problem but cannot guarantee that bad splice was the only problem. Time will tell. I am posting a copy of my notes for reference.
Thanks everyone for your insights and help.
Torque Derate Sequence of Events
For a failed UQS sensor, the ECM will impose the following inducement strategy. When the ECM recognizes the issue with the sensor the check engine light will illuminate for one hour with no engine power derate. After one hour, a 25% derate will be applied for four hours, unless the issue is resolved. In that case, engine power will be immediately restored. If the issue is not resolved within 5 hours of the check engine light coming on, a 40% power derate will be ramped in until the ECM determines it is safe to limit the truck to 5 mph. At this stage, if the fault goes inactive, the ECM will be “sensitive” to SCR faults. For the next 40 hours, after vehicle speed has been restored, any SCR tampering fault will send the truck immediately back to a 25% derate and starts the cycle over again. However, after 40 hours of no active faults, the timer will be reset, and all will be good.
The 5-mph limit will not be applied until the ECM finds it safe to restrict vehicle speed. The truck will not immediately reduce speed to 5 mph on the highway, even if the timer threshold has been met. The ECM would need to see an extended idle time, a key cycle, or a fuel refill to apply the 5-mph limit. With an EGR or SCR system fault that is not a UQS or non-circuit error SCR system fault, only torque derate 1 will be enforced. A circuit error such as a disconnected tank sensor, def pump, NOx sensor, tank heater, or dosing valve will result in an SCR system tampering condition. A tampering condition will follow the warning, derate 1, derate 2, and severe derate process.
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