On this 1994 Honda Civic, the Haynes repair manual has a black and white photograph which shows the DLC (Data Link Connector) as a two-pin connector to jumper to cause the check engine light to flash trouble codes. The wiring diagram shows the DLC having THREE wires: One has power, one goes to ground, and one goes to the PCM (engine computer). /// Under the right corner of the dash are two BLUE connectors, a two-pin, and a three-pin. Their wire colors do not match the colors on the wiring diagrams for the DLC, nor the SRS (air bag) “SCS Service Check Connector”. I DO NOT want to, haphazardly, put multimeter test voltage into the SRS system, in an effort to find where the wires go, if the connectors are SRS connected. Resolution?
Your first mistake is believing a wiring diagram out of a Haynes manual. These manuals aren’t very accurate when it comes to wiring diagrams. They sometimes don’t even show electrical components that are in the circuit. Been burned by that a couple of times.
Everything I have shows you jump the two pin connector to get the Check Engine light to flash DTC’s. They even warn you not to jump the three pin SRS connector.
We had a 93 Civic once and the P2 connector had two wires to it and if I remember right, it also had a dust cover.
I did further research, and it seems like it’s a confusion of terms. The blue two-pin connector is the “service check connector” which one jumpers which causes, both, the check engine light and the SRS light to flash their respective trouble codes. The three-pin DLC (DATA Link Connector) is, evidently, for use with a Honda scan tool. On other OBD1 (On-Board Diagnostic) cars, two DLC terminals are jumpered to cause the check engine light to flash the engine trouble codes. The DTC code flashed by the SRS was DTC 1-1 “Open in the driver’s airbag inflator, or increased resistance”. Possible cause, somebody installed (messily) a Viper 1 Security System.