They also seem to be soldered into the circuit board.
If the LED is not missing (as in the linked thread), the other thing to check is for cracks in the solder where the ends of the LEDs are attached to the printed circuit board. This is a very common problem in the 3rd gen overhead seat belt and airbag warning light assembly. In this case, it’s the joints for surface-mount resistors and in the photo below the cracks are quite visible, but sometimes magnification is required to see them.
[Source: Post #229 in 2006 OBW – Airbag Light On – My fix]
Do you have a good digital multimeter with a “diode check” range? If so, and if the LED can be accessed on both ends with the test lead tips, it can be checked for basic continuity using that DMM range. (Measure with the test lead tips connected one way, then again, reversed. Compare the readings on the AT Oil Temp LED with others that are working.)
In the CVT Diagnosis section of the FSM there’s a page “AT OIL TEMP Warning Light Display”. It provides some things to check. Also, in the “Combination Meter System” section of the “Combination Meter System” chapter of the FSM there’s a cluster self-check that can be run.
The warning lights are controlled by a microprocessor in the cluster, based on information it gets from various control modules, such as the ECM, TCM and BIU. The modules communicate with the cluster via the car LAN, i.e., not by separate wires. The LAN, in this respect, is quite reliable, as are the modules.
