Quote:
Originally Posted by Mondaveo
Thanks, it is interesting to know. I have wondered why in FORScan there is only one GISS reading exposed on the TCM, given there are two shafts. I had thought it would allow me to see the raw values of what you say are in fact three sensors, but it doesn't. Presumably there's some aggregation going on to give the one GISS reading? |
This can get a bit confusing.
Here's how I think it goes ATM:
Forscan has RPM, GISS, VSS.
The first speed sensor is detecting the engine output speed via the clutch housing. That's RPM. But in the P0715 description the words 'input shaft' are used, so a terminology issue.
The other two speed sensors are detecting the two gearbox input shaft speeds, which are driven by clutches 1 & 2. These are coaxial shafts.
There are also two gearbox output shafts, the ATSG manual shows input shaft 1 speed sensor being read 'via output shaft 2'. I suspect that might be Forscan's VSS, making GISS input shaft 2 speed (via output shaft 2). One of these shafts will be freewheeling depending on the gear selected.
So ATM I'd say P0715 refers to a fault in the RPM (aka 'input shaft') sensing system, the sensor for which is dangling in Manchu's photo.