Narrative:

Cruising at FL340 the master caution illuminated. Our investigation revealed the engine light on with both electronic engine controls (eec) in the altn mode. As we were completing the eec alternate mode checklist in the QRH the autothrottles disconnected and we now noticed IAS disagree and altitude disagree messages on both primary flight displays (pfd). ATIS had shown the weather in [destination] to be IFR with ILS approaches in use. As we discussed our problem it was determined to [advise ATC]. We were in IMC going to an IFR approach at the beginning of our STAR procedure and the aircraft was less than what we desired for continued flight. Center allowed us to begin our descent so we could look for VMC as other aircraft reported this ahead.having the IAS and altitude disagree displayed caused some distraction to our process. The pilot monitoring (pm) kept referring to the end statement of the checklist - disp source - but it was not displayed to us. We moved to the airspeed unreliable checklist while continuing our descent. The pilot flying (PF) had originally set -1000 in the vertical speed and power to 77 percent to accomplish our descent. The PF now felt like manually flying the aircraft would give a better feel of the performance. It was very difficult to not be distracted by our pfds since they both showed different airspeeds (PF = 200 IAS and pm = near redline).as we were accomplishing the airspeed unreliable checklist both messages cleared on the pfds and we entered VMC conditions. We landed in ZZZ uneventfully. Maintenance ran multiple checks before they cleared the aircraft for flight. Maintenance said the system probably had water in it.

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Original NASA ASRS Text

Title: B737-800 Captain reported several fault messages along with airspeed and altitude indication disagreements in cruise at FL340. Discrepancies cleared up when the aircraft descended into VMC.

Narrative: Cruising at FL340 the Master Caution illuminated. Our investigation revealed the ENG light on with both Electronic Engine Controls (EEC) in the ALTN mode. As we were completing the EEC ALTERNATE MODE Checklist in the QRH the autothrottles disconnected and we now noticed IAS disagree and ALT disagree messages on both Primary Flight Displays (PFD). ATIS had shown the weather in [destination] to be IFR with ILS approaches in use. As we discussed our problem it was determined to [advise ATC]. We were in IMC going to an IFR approach at the beginning of our STAR procedure and the aircraft was less than what we desired for continued flight. Center allowed us to begin our descent so we could look for VMC as other aircraft reported this ahead.Having the IAS and ALT Disagree displayed caused some distraction to our process. The Pilot Monitoring (PM) kept referring to the end statement of the checklist - DISP SOURCE - but it was not displayed to us. We moved to the Airspeed Unreliable Checklist while continuing our descent. The Pilot Flying (PF) had originally set -1000 in the Vertical Speed and power to 77 percent to accomplish our descent. The PF now felt like manually flying the aircraft would give a better feel of the performance. It was very difficult to not be distracted by our PFDs since they both showed different airspeeds (PF = 200 IAS and PM = near redline).As we were accomplishing the Airspeed Unreliable Checklist both messages cleared on the PFDs and we entered VMC conditions. We landed in ZZZ uneventfully. Maintenance ran multiple checks before they cleared the aircraft for flight. Maintenance said the system probably had water in it.

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.