Error 15 Vehical distance error

We got this error 15 on my brothers 88 doge grand caravan the book says it is a Vehical distance error. Any idea what that means????

Check the wiring connector on it to make sure it's tight and not damaged.

Description and Operation

The distance sensor is located in the transaxle extension housing and signals vehicle motion to the SMEC by generating eight pulses per axle shaft revolution. The SMEC uses this signal along with signals from the throttle position sensor to determine between a closed throttle deceleration and a normal idle condition, thereby allowing the SMEC to maintain desired control of the AIS motor.

http://pic17.picturetrail.com/VOL856/1102933/2077148/125867401.jpg

thanks.