The connector road from the westbound 10 Freeway to the northbound 57 Freeway was reopened about 2:30 a.m., said CHP Officer Jennifer Connolly.
The same road was closed for about six weeks starting on Feb. 18, when a large section of embankment fell onto one freeway transition road and endangered another.
Crews rebuilt the hillside and seeded it after the first slide -- at a cost of about $3.25 million.
Since April 25, crews terraced parts of the hillside, installed new drainage pipes to drain water from inside the hillside, and compacted the soil, Caltrans reported.
Autobahn Construction of Orange was awarded the emergency contract valued at $2 million.
The closure has snarled traffic at the big four-level-high interchange, where the 10, the 57, and the Corona (71) freeways come together.
The roadway is normally traveled by about 27,500 motorists daily.
Caltrans said the connector may be closed periodically at night for additional repairs.
It prevents traffic leaving the Pomona area on Interstate 10 from driving north on Route 57, which connects to the Foothill (210) Freeway at San Dimas. Traffic transitioning from the northbound 71 to the northbound 57 was also blocked last February, but was not restricted in the latest closure.
During the last closure, the CHP suggested that motorists either use the Ontario (15) or San Gabriel River (605) freeways to go north. Using the Pomona (60) Freeway to get to the 57 was discoraged, because it does not have direct ramps to the northbound 57.