Any Unknown or Unlisted Aircraft Manufacturer
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Confusion
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance
Human Factors
Original ATC clearance was the NEWARK FOUR (EWR4) departure off of runway 4L. The EWR4 calls for a left turn to 060 at 500 feet; then at 4DME IEZA a left turn to 290. The clearance was amended via CPDLC before pushback to fly runway heading until 4DME IEZA then left turn to 290. The change was briefed at the gate and again prior to takeoff. Heading 290 was preselected in the Flight Control Panel. After takeoff; at 500 feet; I asked for heading select. I initiated a turn to 290 between 500 and 1000 feet instead of waiting until 4 DME IEZA. ATC questioned our heading then said we were supposed to wait until 4 DME for the turn. A heading of 310 was issued.
Captain reported turning too early contrary to the amended departure procedure.