Bad Knock sensor

[TWRViper]

I'm working on a 1990 NA automatic. I'm getting code 52 = Knock sensor and 25, 26. The owner said the knock sensor was just replaced a week ago.

I cleared the codes and I get code 52 within 1 min of driving. I checked for continuity between the knock sensor pigtail and the wire right before it goes to the computer under the dash.

Is this a common problem with the 1990 supras? Is there anyway to check if the sensor is bad or the wiring?

Thanks for the help

Tom