2011 M37S with Sport Technology Option. 150K Miles. Drove slowly over a wavy road and the 4WAS Light illuminated. Drove it home without 4WAS, Cruise Control, ABS, Traction Control. They all enter Failsafe Mode when there is an error as they share signals. Took it to my local Infiniti Dealer. They told me it was the ABS Actuator. $1500.00 to fix. I said the code indicates a 4WAS issue. They consulted with Infiniti Tech Services and they want to replace the entire KYB Rear Steering Rack for $6200.00. They offered $500.00 off the part. I declined and brought the car home. Pulled the Motor off the Rear Steering Rack. (2 Bolts and one Electrical Connector) Tested good with 12 vdc. Reversed leads and the Motor ran the other direction. Took off the Rear Steering Sensor. (4 Bolts and one Electrical Connector) Tested and retested it according to the Infiniti Shop Manuals (PDF's you can download free). Sensor tests "no continuity" or "open" on all 4 pins. My $99.00 Blue Driver Code Reader reads all Infiniti Codes and allows me to Reset groups of Codes. I have purchased a 2006 - 2010 G35 Rear Steering Rack that has the same Motor and Sensor as my M37 for $172.00 delivered. I will keep the Motor and Sensor if they test good. I don't the need the G35 Rack as it is different. If they do not test good, 30 day returns are allowed. Honestly, I suspect a wiring issue more than a failed Rear Rack Angle Sensor but the Code (1918) and the bad Sensor are compelling evidence to change out the Sensor. Google "Infiniti 55705" and you will see there are many used Rear Steering Racks available. Don't worry about the "-" and second part of the Part Number. I suspect it is for the Mechanical Rack. Part is scheduled to arrive on Friday October 11th. Today is Monday October 7th. We will know on Saturday October 12th if this is the problem, not the problem, or one of many problems. My Rear Steering Rack looks to be in good shape with no rust, damage, or leaking fluid. If this fixes the problem I think I will need a Rear Steering Sensor Calibration (Code) that has to be done with the Consult III or IV System at the Dealer. Stay tuned for an update. This is now a challenge for me to figure out and fix. I have other cars to drive so there is no big urgency to fix the M37.