No power to speed sensor

[Rawze]

Register your engine/truck on quickserv.com (free) -- look up the wiring diagram for the ecm and it will tell you how and what is wired to the ecm.

What make/model truck?
What version of the ISX? (CM2250? CM2350-X101?)

-- Also, just because the speedo stopped working does not mean its the speed sensor. Peterbilt and KW's are notorious for speedo in the dash to stop working properly, it is a common failure for them.

some notes: Not sure it applies to the ISX specifically, but something to consider ...
Many types of speed sensors do not even need to have a voltage going to them. Speed sensors can often use what is known as "variable reluctance magnetic sensing principle". This means it generates an alternating voltage (like an alternator does but on a much smaller scale) when the tail shaft is turning/moving and the ecm reads this, measures its frequency like a magnetic pick-up coil similar to reading the music on a cassette tape. If it is one of these types of sensors, there will not be anything coming out from the ecm that can be measured.


just some other things to consider/think about.