As many of you have experienced, we had a rear wheel speed sensor fail last fall on a long trip away. The three symbols on the dash indicate no abs, traction control and cruise is inoperable.
I used my Autel 619 to check for codes but none showed up.
Our dealer, Star Motors here in Ottawa (a terrific store I might add!), diagnosed a right rear speed sensor and replaced it. $700 later it's all good.
Fast forward to this past weekend on a trip to La Malbaie just east of Quebec City, and at a gas stop, on starting the trio appear once again! Boo.
I finished the trip without cruise and on arriving home read lots on sprinter-source about how the sensors can become fouled and give inaccurate readings. So I crawled under the rig and removed the sensors from the rear hub. It was much easier than I expected! Initially I removed the duallies, only to learn that wasn't necessary. There is a 8mm torx nut on the rear of the hub that holds the sensor in place, accessible freely. So I removed the zip ties and the sensor and the right was grungy, not so the left.
I reinstalled and drive the rig, with no change. Boo.
I called our service advisor, and found the tech at Star Motors was on holiday till next week. So I ordered the left side, figuring that if the right was replaced, it must be the left! And if I was wrong they would warranty the right side. I also asked if a reset of the ECU would be necessary and Martin (our advisor) said no, "they should be plg and play".
That got me thinking about computers...so I unplugged the sensor connections from the canbus on the cross member just ahead of the rear axle. They are supposed to be weatherproof, but we all know about the nature of the Curt rear signal controller! There was a fair amount of dirt around the connection, but internally looked ok. Interestingly the left and right connections are different!
I reconnected and started, and drive off and the lights went away! Woohoo!
Maybe they'll come back on, or maybe the connection was just slightly loose? But I have my cruise back and more knowledge about how these things work.. The first photo is the Torx socket, the second the back of the hub and the third the sensor connections on the rear face of the cross member.