When a 2001 - 2004 Ford Escape air bag light flashes code 36, one of four problems could exist in the circuit from the Restraints Control Module (RCM) to the left side air bag (the side air bag in the seat, not the main air bag in the steering wheel):
1. DTC B1992 - Left side air bag circuit short to battery or ignition
2. DTC B1993 - Left side air bag circuit short to ground
3. DTC B1994 - Left side air bag circuit resistance high
4. DTC B1995 - Left side air bag circuit resistance low
In order to determine which of the four Diagnostic Trouble Codes (DTC) exist, you will probably have to have the codes scanned at a repair shop. Most trouble code scanners available to the DIY mechanic only scan for powertrain codes.
It is likely that you have code B1994 (left side air bag circuit high resistance) since Ford has issued a Technical Service Bulletin (TSB) for this code. The same service bulletin applies to code B1998 (same problem, right side air bag). The TSB states that this problem can be caused by a variation in electrical continuity at the electrical connector to the side air bag. The connector is located under the seat. Ford makes a replacement body harness pigtail connector (Ford part number 1L8Z-14A411-A) to fix this problem.
I had the same air bag trouble code 36 flashing intermittently on my 2004 Ford Escape which I bought used. In my case, I discovered that a Ford dealer had already replaced the pigtail connectors on both the left and right side air bags. Using my multimeter, I found high resistance in one of the pigtail splices that was made by the repair shop. They had just twisted the wires together and then sealed the connection with heat shrink tubing. I fixed it by making a solder splice and sealing the splice with heat shrink tubing.
You can identify the replacement body harness pigtail connectors because the wire color code is a bit different than the original. The replacement pigtail connectors have one WHT/LT BLU wire and one WHT/YEL wire (same replacement pigtail connector for both left and right). The original wire colors are:
Left - RED and WHT/LT BLU Right - BRN/YEL and WHT/YEL The side air bag connectors are located under the seat (driver or passenger). The wiring from either of these connectors goes directly to the RCM which is located under the center of the dash. The RCM is bolted to the transmission tunnel. There are two electrical connectors on the module. The side air bag wires are located in the smaller connector and can be identified by color code as described above. When you remove the electrical connector from the RCM, each pair of wires going to the side air bags are shorted together in the connector (safety feature to prevent accidental deployment of the side air bags). With the RCM connector removed, you can unplug the connector under the seat and place your ohmmeter across the two terminals located in the body harness side. There should be less than 1 ohm resistance. In my case, I found anywhere from about 0.5 ohms to around 65 ohms as I moved the wires around. If all Ford dealers make the repair by just twisting the wires of the replacement pigtail connector together, I would imagine that there are a lot of folks out there experiencing this same problem intermittently.