Thanks for the post, however, it is a few years late; we identified the 3 7 code back in 2004( posted earlier in this thread ).
Unplugging and reattaching the yellow cap does nothing to resolve the 3 7 code for me now. I have even replaced the yellow caps several times with new ones and still have the code.
Friend,
Now I can tell you with confidence that code 37 is the result of the passenger side air bag substitute resistor (the yellow one under the passenger seat).
Today I have the chance to borrow a scanner from a friend and analyze the problem. First, the scanner gave code B1998 which is "Passenger side airbag circuit resistance is high". I though there may be an intermittent open circuit so I decided to check close to the plug going to the Restrain module.
I disconnected the battery and waited for few minutes then I unplugged the smaller connector. I cut the two wires, Brown/Yellow and White/Yellow. I measured the resistance and found it to be 9.6 ohms (the ohmmeter leads’s resistance is 0.2 ohms).
I unplugged the resistor under the driver side and measured the resistance and found it 6.9 ohms and became suspicious. I need to say that I bought that vehicle about 6 months ago and it had the airbag problem then and do not know much about its history.
I decided to simulate the driver side resistor, so, I brought two 10 ohms resistors and connected them in parallel (twisted the two ends together) and that gave me 5.1 ohms (may be close enough!!!). I connected the combined resistors to the wires going to the plug and plugged the connector and connected the battery.
When I scanned again, I got the code B1999 which is "Passenger side airbag circuit resistance low". So I figured it was looking for a 6.9 ohms.
I brought three 22 ohms and connected them in parallel and that gave me 7.6 ohms and used them to replace the 5.1 ohms I tried before and then scanned.
WOW. No more errors. No more flashing just the regular ON for few seconds and OFF. I turned the vehicle on and off several times and no code is generated.
Conclusion, it was the resistor (yellow plug) under the passenger seat and it needs to match the one under the driver seat. In my case (99 explorer Eddie Bauer, 4.0L) the resistance is 6.9 Ohms.
Hope this will help someone to diagnose his Airbag code 37 problem.
Note: I did not replace the under seat resistor, I left my three parallel 22 ohms resistors in place and isolated them well.