No, I checked the e-brake, and it isn't the problem. It will switch the light on and off just fine (and when the light had stayed on I kept the e-brake off and pulled the sensor plug, which killed the light).

My official '94 service manual makes it look like the sensor is in the cap, but it clearly is not. The book shows wires coming off the cap, but mine has the plug on the side of the reservoir. I *think* it's the original. When I got the rig it had 57K miles, I question that the PO had changed the MC by then. I've got 194K on the truck now, I just wish more of those miles were on dirt!