2004 S40 speedometer fails on hitting a bump
 

2004 S40 1.9 base model. Over time the speedometer fails more frequently when hitting a pothole. This happened once a year until recently. Volvo reprogrammed the speedometer to no avail but did diagnose both front wheel speed sensors as faulty. This repair is scheduled. The transmission output speed sensor has been replaced. There is no ABS light on and never has been on. Will the replacement of the wheel speed sensors correct this or am I wasting more money. The cruise control is erratic as well.There are no other codes or fault warning lights. Does anything else affect the speedometer? Thank you

Update: I replaced the ABS sensors on both front wheels, cleaning (gently) the tone rings. The speedometer fails less often when hitting a pothole but still happens. Found a used cluster and will replace it. I was told it does not require any DIM programming.

intermittant electrical problems are a bit of a crap shoot when diagnosing. the speed sensors talk to the ABS controller which in turn talks to the transmission computer then the ECU so anywhere there's a connector or a circuit board, you can find a fail. On other older models the ABS controller circuit boards were prone to cracks in the solder joints which could create intermittant fails. Check out some of the repair vendor web sites to see if they show your model and similar symptoms - Rocha-tek, Midwest ABS, Xemodex are three I can think of.