My 2002 DHS had a problem with the airbag system. The light would stay on mostly but occasionally go off while driving. Fortunately with the help of some forum members I was able to complete the repair for $150 round trip. I'd like to summarize and share this in short form.

Symptoms: Airbag light is on and using the built in diagnostics on the DIC to retrieve codes yields a "No SDM Data" message

Two Possibilities: A loose or corroded plug on the SDM module or a defective/dead SDM module. For me it was the latter. I began sourcing a replacement module and found a refurbished unit for $100 on with a warranty.

Tools Used: Fuse puller, 10MM open end wrench, small pick/hemostat, torque wrench set to 80 in/lb, a 10MM socket and ratchet

1) Disable your airbag system by removing the SIR fuse or disconnecting the battery all together. The fuse box and battery are both under the back seat. There's no need to wait for power to dissipate because by the time you "dig in" and reach the module any residual power will have been long lost from the system.

2) Remove the center console. On my DHS there are four 10MM bolts, two on each side. To access the two rear ones move both front seats as far forward as they will go. The bolts will be partially obscured by the seatbelts but can be removed with a little finagling. To access the two front bolts, move both seats as far back as they will go. The bolts will be on each side between the console and the track for the seat. Once the bolts are out, lift the console up and out of your way. I simply propped mine up. Unbolting the console is truly the hardest part of the job.

3) With the console out of the way you will see a slit in the carpeting. Pull this open and you will see the SDM module. Photo below shows the SDM module uncovered.

4) Use the small pick/hemostat gently dislodge the tangs on blue keeper pin and work it straight upward and free. Next take the grey lever and move it all the way to the right which will unlock the connector from the module. You'll need to press in slightly on the back of the yellow plug to allow the grey lever to unlock and slide past. At this point you may try cleaning the connector and the module's pins with electrical contact cleaner if you suspect a poor connection. Be sure everything is COMPLETELY dry before reconnecting, powering up the system and testing. If you still have the light then you likely have a bad module. Disable the system again, take a 10 minute break while the system looses any residual power and proceed to next step

5) With the module's plug disconnected, loosen the four mounting nuts and pull the module free. Gently pry off the metal shield on the bottom of the SDM and transfer it to your replacement if it did not come with one.

6) Install the replacement module and torque the attaching nuts to 80 in/lb. I did mine in two steps (40+40) in a criss-cross pattern to ensure even tightening (I'm fussy with torquing fasteners). Next gently insert the plug. It's keyed (via the clear plastic portion on the plug) to aid in instalation. If this clear plastic part of your connector fell apart on removal like mine did don't worry. You'll just be extra careful lining the connector up with the pins in the module. Do not force it or you will damage the pins! Easy is the key here. When correctly positioned it will require almost no effort. Once pushed in, slide the grey lever back to the left to lock the connector firmly in place. Re install that blue keeper pin from step 4.

After installing the car's VIN may need to be programmed into the new SDM or a relearn procedure performed by your local Caddy dealer (even if the light turns out and seems ok). I took mine to my local Caddy dealer and they performed a simple relearn using their Tech 2 for $50 while I waited. Apparently my 2002 did not need to be completely reprogrammed but yours may be different. I have heard that some may still have an airbag light and a code pertaining to mismatched components until reprogrammed. Either way the "No SDM Data" code should be gone after installing a working SDM. No SDM Data = bad SDM module. Remove, replace and reprogram

Special thanks to everyone here for their help and contributions to this fix.