Date: 202004
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: EMB ERJ 170/175 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
Aircraft component: Fan Reverser
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Technician
Reporter qualification: Maintenance Powerplant; Maintenance Airframe
Human factors: Communication Breakdown; Confusion; Time Pressure
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Pre-flight; Aircraft In Service At Gate
Result: General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft; Human Factors; Procedure
Primary problem: Human Factors

Narrative: We had a situation for Aircraft X due to and ENG 2 no dispatch message due to Ignition Channel B fault. When troubleshooting Maintenance found the connector/switch to the EHCL (Electro-Hydraulic cowl lock) broken. The MEL was applied for the ENG 2 Thrust Reversers. At this time there were no Maintenance personnel available to due an ENGINE run after they swapped E2 igniter plugs from channel A to B and B to A IAW the MEL. The Mechanics turned over the aircraft to the next shift to complete the Engine Runs. I arrived and retrieved the logbook and went with another mechanic to complete the Engine Runs. We performed the engine runs and called aircraft back into service approximately 30 mins prior to first departure of the day. We then recieved a call from [Maintenance Control] approximately 10 minutes prior to departure saying the pilot is reporting ENG 2 Rev INHIBIT message not being displayed on EICAS IAW MEL. Instead ENG 2 REV PROT FAULT displayed. The MEL that was signed off as previously c/w referenced AMM so we started there and found that it referenced AMM deactivation of the ICU(Isolation Control Unit). While following the AMM for Deactivating the ICU I saw that it said open Circuit Breaker and install a CB ring on E2 REVERSER CB as well as making sure the ICU inhibition lever was in the inhibit position with the quick release pin installed to make sure the lever is making contact with the micro switches. The lever was in the inhibit position but the quick release pin was not in the correct position. I moved the pin to the correct position and followed the last step of the deactivation process which was to make sure the E2 REV INHIBIT MESSAGE is shown on EICAS which it was. At this point I did not see in the ICU deactivation procedures of closing the CB and removing the ring as it was not in that part of the AMM. Instead of going back and referencing the AMM section the MEL had me go to and discussing with the other mechanic of whether or not we should close the CB we determined that it was not in the DEACTIVATION procedures so we should leave it open since the discrepancy was corrected. I should of referenced back the original AMM to make sure I followed the JOB CLOSE UP section as this would of told me to remove the CB ring and close it upon completion of deactivating the TR. Since the MEL was done by the prior shift I did not think to go back to that reference as I only performed the ICU deactivation even though I know that all AMM sections have a JOB CLOSE UP section. I also think the several Human Factors played a role in my error. The STRESS and PRESSURE of the plane being delayed after being [on ground] for a long period of time DISTRACTED me from being focused on reviewing my work and the AMM. I also had a LACK OF AWARENESS to realize the ICU deactivation did not have a JOB CLOSE UP SECTION. I think it would be helpful to add this section to the ICU deactivation part of the AMM to state if no other Maintenance is being performed to complete this section.




Synopsis: Technician reported misreading MEL procedures and not correctly accomplishing MEL procedures when deactivating a thrust reverser.