Quote:
Originally Posted by rondeo
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.
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Ah, thank you my man! That changes the interpretation of my graphs and could be a breakthrough. If input sensor = "RPM" then I should see any evidence of the erratic signal on that line, rather than the line for "GISS" as I'd thought. And indeed I do have a squiggly trace for "RPM" in many instances where the gearbox shifted awkwardly. I had attributed that as a result of changing engine load with the clutch dis/engaging but it looks like it could be the evidence I was seeking.
The interesting thing now would be to compare the "RPM" exposed by the
TCM with a recording of the actual RPM at the engine (
ECU?). Unfortunately I don't think FORScan allows me to live stream from two different modules at once...
(BTW, I think you mean Bundy's photo?)