Code B121, Twilight Enable Switch Circuit (Riviera Only): Notes

Fig 1: Code B121 Flowchart, Twilight Enable Switch Circuit (Riviera Only)

Fig 2: Code B121 Flowchart, Twilight Enable Switch Circuit (Riviera Only)

Fig 3: Code B121 Schematic, Twilight Enable Switch Circuit (Riviera Only)

The twilight enable switch uses the same physical control as the delay pot. Inside the left switch assembly, the enable switch contacts close as soon as the time delay slider is moved off of its extreme minimum (off) position. The BCM supplies a voltage on circuit 304 to the switch. When the slider is moved from the off position, the switch contacts close and the signal voltage is pulled low through ground circuit 804.

Code B121 will set if the ignition is on, the twilight delay pot has not failed (Code B120), and the signal voltage is high when the delay slider is moved from the off position (open circuit).

1. BCM input value BI82 displays the voltage state of the circuit at the BCM. These conditions can be observed in BCM input display BI82 as readings of "HIGH "or "LOW" when slider is moved.
2. Checks to see if the "HIGH" reading is due to the circuit or the switch assembly. If the display changes from "HIGH" to "LOW" after jumping the switch assembly terminals, the BCM and wiring are okay.
3. Checks to see if the "HIGH" reading is due to the circuit or the BCM. If the display changes from "HIGH" to "LOW" when the BCM terminal cavity is jumped to ground, the BCM is okay.