2015 Coronado glider. 12.7 Detroit. Eaton 13 speed.
A year ago I lost my Speedo and cruise completely. A few weeks before that the Speedo wouldn’t work right away as I got rolling every morning but after a few miles it would come back to life and operate normally for the rest of the day. It did progress to malfunctioning at different times every day and the last day it worked it canceled the cruise along with it. ALL OTHER GAUGES WORK FINE.
flash code 54 or spn84 fmi12 which lead me to the vss on the transmission. It was cheap so I replaced it but it didn’t change anything.
I found a diagnostic procedure from Detroit for a flash code 54 and everything checked out as far as wiring. I finally got around to bringing my laptop with me to see if I had a road speed signal in diagnostic link but it does not. However I do use a scangauge and it does show a road speed through the 9-pin.
my research shows that the road speed to the 9-pin and road speed to the gauge are two different signals which leads me towards testing the signal between the ECM and the gauge. But I don’t know how.
I ALSO REPLACED THE LCD LIGHTBAR FOR $1200, BEING ITS THE INSTRUMENT CLUSTER BRAIN.
someone told me that I should be looking at replacing the cpc but I don’t believe this truck has one as it is a glider and it’s essentially built on the old school century class platform but I could be wrong. He told me it should be in the passenger side b-pillar but there is no access like on the driver side, and the PDM and ABS computer are the only things on the driver side.
The company I’m leased to also is on me to get it fixed because there is an ELD in the truck for a camera. That doesn’t work either. No connection to the truck. The ELD did work for a time after the Speedo stopped working, but not for long.
Could anyone send me in the right direction even if it’s starting over? I have a bad ankle and would love to have my cruise control fixed for the long stretches.
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