Narrative:

Attempting to get off the gate in den was difficult; frequency congestion made it very hard to get a word in. After pushing back from the gate; we started engine one. Received taxi instructions and proceeded to our spot. Switched to ground and received taxi instructions to [runway] 25. At this point; I went heads down and started programming for [runway] 25. I told the captain I was ready. Captain called for the runway performance change checklist. The checklist was completed in full because we were setup for [runway] 34R. Captain called for the before takeoff checklist. I did my flow including the takeoff configuration; and we finished the checklist. Tower instructed us to 'lineup and wait runway 25' I read that back to tower. The aircraft in front was then cleared for takeoff. This had our attention; as it was not standard. Approaching runway 25; captain stated 'runway 25 confirmed'. I turned on all the lights. After lining up with the centerline; the captain stated 'heading checks'; I repeated 'heading checks'. Tower cleared us for 'takeoff on 25 RNAV [fix]'; I read that back. The captain started to advance the thrust levers and I looked at the icas and noticed engine 2 was not started. I stated 'engine 2 not running' the captain brought the thrust levers back to idle. I told tower we were going to turn off the runway. Tower cancelled our takeoff clearance and asked if we needed assistance. I stated 'negative'. We started engine 2; waited 2 minutes; advised ready and flew to [destination] without incident. Distraction during taxi concerning the change of runway. Frustration with the ramp circumstances. Lack of verifying the engine was running on my part before initializing the before takeoff checklist. Distracting circumstances with the takeoff runway. Making a verification of engine status a step in a flow or checklist. As painfully obvious as it may be.

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Original NASA ASRS Text

Title: ERJ-175 flight crew reported rejecting takeoff after recognizing that the second engine had not yet been started.

Narrative: Attempting to get off the gate in DEN was difficult; frequency congestion made it very hard to get a word in. After pushing back from the gate; we started engine one. Received taxi instructions and proceeded to our spot. Switched to Ground and received taxi instructions to [Runway] 25. At this point; I went heads down and started programming for [Runway] 25. I told the Captain I was ready. Captain called for the Runway Performance Change Checklist. The checklist was completed in full because we were setup for [Runway] 34R. Captain called for the Before Takeoff Checklist. I did my flow including the takeoff configuration; and we finished the checklist. Tower instructed us to 'lineup and wait Runway 25' I read that back to Tower. The aircraft in front was then cleared for takeoff. This had our attention; as it was not standard. Approaching Runway 25; Captain stated 'Runway 25 confirmed'. I turned on all the lights. After lining up with the centerline; the Captain stated 'heading checks'; I repeated 'Heading checks'. Tower cleared us for 'takeoff on 25 RNAV [FIX]'; I read that back. The Captain started to advance the thrust levers and I looked at the ICAS and noticed engine 2 was not started. I stated 'Engine 2 not running' the Captain brought the thrust levers back to idle. I told Tower we were going to turn off the runway. Tower cancelled our takeoff clearance and asked if we needed assistance. I stated 'negative'. We started engine 2; waited 2 minutes; advised ready and flew to [destination] without incident. Distraction during taxi concerning the change of runway. Frustration with the ramp circumstances. Lack of verifying the engine was running on my part before initializing the Before Takeoff Checklist. Distracting circumstances with the takeoff runway. Making a verification of engine status a step in a flow or checklist. As painfully obvious as it may be.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.