Test J: The Front Display Interface Module (FDIM) Illumination Does Not Operate Correctly

PINPOINT TEST J: THE FRONT DISPLAY INTERFACE MODULE (FDIM) ILLUMINATION DOES NOT OPERATE CORRECTLY

Normal Operation
The FDIM receives the illumination signal from the smart junction box (SJB), and dims the illumination based on the position of the dimmer switch.

DTC U0140 (Lost Communication With Body Control Module [GEM]) - sets when the FDIM is missing messages from the SJB for ignition state, illumination, or delayed accessory. Because a missing ignition state or delayed accessory signal would cause multiple symptoms (since many modules would report this error), only the illumination signal is diagnosed in this pinpoint test.

In order for the FDIM to set DTC U0140, the illumination signal must be missing for greater than 5 seconds. In the event this signal is lost, the FDIM defaults to full night time brightness, resulting in a symptom of the FDIM being unable to dim.

This pinpoint test is intended to diagnose the following:
- Interior lamps system concern
- FDIM

J1-J2: