Commercial Fixed Wing
Maintenance Airframe; Maintenance Powerplant
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Aircraft; Human Factors; Procedure
[We] were working on the LH (Left Hand) engine on Aircraft X troubleshooting the Left Engine Fire loop 2 issue. We found that the LH Engine Fire loop wiring for Loop 1 fire loop from the pylon connector to the  loop 2; connected to the wrong fire loop. Loop 1 wiring was/is connected to Fire loop system Number 2; wiring for loop 2 system for the fire loop from the pylon connector to the Number 2 loop is connected to the wrong fire loop. Loop 2 wiring is connected to fire loops system Number 1.
Maintenance technician reported that an engine fire warning loop was improperly installed; causing a safety hazard.