The crew's write-up was that the left wing spoiler "green" box did not show with a full left wing down turn. This check is done as part of the flight control verification after push-back and before take-off. It entails cranking the control wheel full hard left and right.
There is some confusion about the configuration page display. The inner box is the spoilers and the outer box is the ailerons. In the case of the spoilers, #3 and #5 are averaged for the display. The aileron display is the average of the inboard and outboard ailerons. From the Schematic Manual 27-66-0, for a green box to show, the spoilers must be greater than 54 degrees up. Schematic Manual 27-14-0 shows the ailerons needing to be greater than 17 degrees trailing edge up/down for the green box.
The image below was not taken from the suspect aircraft, but it shows how position information can be seen from the FCC #1 "sensors" section.
It "is" possible to pull up both FCC's sensor readouts at the same time. We used the #1 MCDU for FCC #1 and the #2 MCDU for the #2 FCC.
The problem with our aircraft was the #3 left spoiler indicated 53.6 degrees at full deployment. We verified the actual position with a protractor to rule out a rigging issue. Once verified as correct, a small adjustment was done on the position transmitter. This image is poor as it was an "extremely" humid day. The sensor is mounted on a bracket and the knurled shaft on the arm connected to the spoiler surface. The adjustment requires loosening the bracket bolt and "slightly" rotating the sensor housing while someone monitors the FCC output display. We matched the output to meet the actual position which was above 54 degrees. After securing the bolt, we had a green box for the left side.
McDonnell Douglas labels the spoilers from wing root out. Another crappy shot, but we're looking at 2 through 5.
AMM 27-66-02-4 for sensor replacement and adjustment.