Was able to help out a kaka sucker that got stuck doing a turn around at our neighbors property here in the Santa Cruz Mountains. Full, the tanker had a 25,000 lb GVWR. I had the tanker dump the fresh water tanks. The Warn Xeon 12s didn't have a problem pulling the pumper.
The technician felt the issue to be ATF running low by 1.5 quarts. The JT only has 9,300 miles, so the conclusion was that the transmission was underfilled at the factory. Low fluid is one possible cause for the P07D9 code.
Almost, your analysis makes a lot of sense. Thanks for sharing. If the harness is not part of the diags, I will now ask for the harness to be inspected.
Encountered P07D9 code, which translates to " Gear 8 Shift Incorrect Ratio ". The JT was using Adaptive Cruise Control (ACC) when the ACC stopped / messaged that ACC no longer possible. Then power dropped and the transmission seemed to slip. Could not get above 55 mph. A restart of the engine...
@karter44 , thanks for this post. I had the same issue. Very helpful. I just swapped the bed lights and they worked. They are marked R and L, too. Same issue, I had Line-X installed and the lights were put back incorrectly. Also, the technician broke a tab on one of the lights.