Date: 201301
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: B757 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
ATC / advisory: Ramp ZZZ
Aircraft component: Powerplant Fire/Overheat Warning
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Human factors: Situational Awareness; Workload; Confusion; Troubleshooting
Second reporter function: Captain; Pilot Flying
Anomaly: Aircraft Equipment Problem Critical
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: Taxi
Result: Flight Crew Returned To Gate; General Declared Emergency; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: After meeting the Captain in Operations; we both had not used the revised flight plan format since training a few months ago. The Captain was shown how to receive the flight papers and the SME started reviewing the new flight plan and performance with us. The Captain and I have flown before on the B757\767 and the B737 back in the day. We were both are familiar and well acquainted with each other. Afterward; we proceeded to the gate. With the extremely cold temperatures; frost covered the exterior of the aircraft which required deicing. We had a wheels-up time approximately one hour after the scheduled departure time. Zone Control still wanted the flight to depart on time. The Preflight Checklist was completed and the Before Pushback Checklist was completed to the line. Once I heard the push crew contacting the Captain; I asked him if I should turn on the beacon and finish the checklist. He acknowledged with a yes; and I did so. The push and engine start was normal. We started the taxi to the deice pad. As we turned in toward the deicing pad; the fire warning bell started ringing continuously. However; the Master WARNING lights never illuminated. The fire warning bell could not be silenced with the Master CAUTION button. Both the Captain and I tried our respective buttons. This made communications within the cockpit and on the radios very difficult at best. The Captain instructed me to shutdown the engines; which I did. The APU was still running. I asked the deicing crew if they saw any indication of smoke or fire. They indicated that there was no visible smoke or fire. I then instructed them not to approach the aircraft. I changed to ZZZ ground and asked them the same thing as well as to send the fire trucks. Ground Control indicated that there was no visible smoke or fire and that Airport Rescue and Fire Fighters were on the way. All of this was done with the Captain's direction and/or common sense dictating the actions. The Captain communicated with the Lead Flight Attendant about the situation and that an Evacuation was not required as of yet. I believe he also made and announcement to the passengers. At that time; I had the Evacuation QRH readily available if needed. After a visual inspection from the Airport Rescue and Fire Fighters (ARFF); it was determined that the fire warning was a false warning and the Captain decided to taxi to a gate. During this time; the Captain was communicating with the ARFF on a unique frequency and indicated that we would taxi back to the gate but would like for the trucks to follow us to the gate. The Captain decided to taxi in versus waiting (who knows how long that would have taken) to get towed in. After arrival at the gate; the ARFF made a more thorough inspection and received a briefing from the Captain as to the suspected false warning. After everything was cleared; the pilot that was working in zone to monitor flight delays met our flight. We briefed him on what occurred. Afterward; he shared with us that the reason he came to meet the flight was to tell us that zone was upset with us because the flight had blocked out; but according to the video camera; the fueler was still hooked up; the belt loader was still at the aircraft loading bags. He indicated to us that zone thought that the Captain had intentionally released the parking brake early and/or pulled the parking brake circuit breaker. I was surprised by the accusations and both the Captain and I strongly denied them. I was too busy with trying to get information from the new format flight plan to even think of such things. One possible explanation is the aircraft had sat overnight at the gate in single digit temperatures; if not below zero. It is possible that the cold temperatures had something to do with the conflict of the out time. Also; the Captain's clock wasn't operating when we arrived at the aircraft. I don't feel that the pilot was accusing the Captain and me of anything; but was just the messenger. We both explainedthe sequence of events and he said that he would share that information with zone control. I indicated to the Captain that I was done after that ordeal (the false fire warning) and that I was going to call the Dispatcher. The Dispatcher answered but was very quick in his tone and just asked how he could help me. I started to explain what had happened; but he said that he had an emergency that he was working and wanted me to get to the point. I basically said never mind and said good bye. Maintenance was on board and indicated that the fire detection card (I believe for the cargo detection system) had been recently replaced. They indicated that they would replace that card to see if it would resolve the problem. Since it was going to be a while; I walked up to the Flight Office to see if there was a Flight Manager available. No one was in the office. I walked back to the jet and about an hour and fifteen minutes after we blocked in; a Flight Manager called to talk to the Captain and me. After having a conversation with the Captain; I talked to the Flight Manager and answered a few questions regarding my continuing on with the ZZZ1 turn. I told him that although I had calmed down from the incident; the adrenaline was pumping for me and I could still feel it somewhat. I didn't want to play 'Monday morning quarterback' on our flight. He asked if I would be good for the next day of reserve and I answered that I thought I would. He placed me on do not fly for the rest of the day.


Second narrative: Report contains no additional information.


Synopsis: During taxi out a B757's aural engine fire warning alerted without the fire handle lights and could not be silenced so the crew called for fire department backup and returned to the gate where the fire warning card was replaced.