As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER T/O DURING CLIMB THE CREW RECEIVED A L/H ENGINE OIL WARNING MESSAGE. CREW LEVELED OFF AT 4000 AND ALL INDICATIONS ON OIL PRESSURE NORMAL. CREW DECLARED EMERGENCY AND RETURNED TO TLH WITHOUT INCIDENT. MX R/R L ENGINE OIL PRESSURE SWITCH IAW CRJ 700 AMM AND PERFORMED FUEL AND OIL LEAK CHECK. NO LEAK FOUND. NO L ENGINE OIL PRESSURE WARNING INDICATION DISPLAYED.