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The trans software uses the input from the turbine speed sensor (on the input shaft) and the output speed sensor to control the shifts in the transmission. With these two inputs the actual ratio across the transmission can be calculated in real time. This information is used to control the pressures during a shift. The same info is also used for diagnostics. If the trans is supposed to be in a certain gear the ratio is calculated and compared to what the ratio should be. If it's wrong a code is stored and the OD OFF light flashes.
Thanks for the fast reply. That probably explains why my OD light kept flashing while on idle in traffic in NYC last Friday. Would that be enough to cut off the engine?
The trans software uses the input from the turbine speed sensor (on the input shaft) and the output speed sensor to control the shifts in the transmission. With these two inputs the actual ratio across the transmission can be calculated in real time. This information is used to control the pressures during a shift. The same info is also used for diagnostics. If the trans is supposed to be in a certain gear the ratio is calculated and compared to what the ratio should be. If it's wrong a code is stored and the OD OFF light flashes.
Darn! Ya beat me to it, Mark!
I stayed at a Holiday Inn Express last night and was gonna post exactly what you wrote, but ya beat me to it!
That probably explains why my OD light kept flashing while on idle in traffic in NYC last Friday. Would that be enough to cut off the engine?
No, an OSS error will not cut off the engine. And you have to be moving to test the OSS, so it is not likely that the OSS was causing the OD light to flash when you were at idle.
I don't mean to be rude by asking a question and not posting back to your reply. Code was P-0722. Parts replaced: Fuse - $0.74, Sensor Assembly - Speed - $32.00, Labor $225.00.
After this brief engine cut-off issue, I was in an accident. Two guys driving a subaru legacy wagon decided to cut in front of me. Tore his wagon like a can opener from front fender to rear fender. Turns out he was uninsured. My only damage was my corner bumper was scraped and pushed in a bit by about an inch. These trucks are marvelous machines.
My ex was doing the same thing. I replaced the speed sensor and everything was fine for a while. The cruise control quit working, then Intermitently the truck would just die at a light. OD light would blink. It acted the same as the speed sensor. I found the fuse for the cruise it was blown and I replaced it it blew again. (just out of curiousity)It turns out that the replacement harness for the brake pressure switch 2 amp fuse did not blow. The dealer had done the harness upgrade but did not replace the brake pressure switch. When I unplugged the harness from the switch it had a bad burning electrical smell. I replaced the brake pressure switch and the fuse it is fixed now. Also fixed my cruise.