Methods and systems for failure point diagnostics in cable telemetry at a wellsite. The methods involve providing a system includes a cable operatively coupling between a surface modem and a downhole modem that is operatively coupled to a downhole toolstring of one or more downhole tools via a toolbus. The methods further involve generating a plurality of test signals, sequentially applying the test signals across one or more test loops in the cable telemetry system, and generating a failure point alert when at least one of the test signals fails in at least one of the test loops. The failure point alert identifies which component of the cable telemetry system caused the test signal to fail.