The suspect was accelerating, hitting speeds up to 90 mph as a tractor trailer in the lane ahead was slowing down.
The GMC pickup crashed into the rear of the 18-wheeler, smashing in the engine block and coming to rest on the side of the freeway as smoke poured out from the hood.
The crash happened on the 5 in the Lincoln Heights area.
Officers shut down the southbound sides of the freeway as they waited with guns drawn but did not immediately approach the smoking vehicle.
After a few minutes, they approached carefully as the vehicle interior was hidden by deployed airbags so they could not see the status of the driver. They were able to pull the driver out of the vehicle and the person appeared to be unconscious.
Paramedics later were treating the female driver and performed CPR as they wheeled her on a stretcher into an ambulance. The suspect, a 43-year-old woman from Valencia, was transported to a hospital in unknown condition.
The chase started with a domestic violence incident in the Santa Barbara area. Authorities found the suspect in Ventura County and chased the black pickup truck over freeways into the San Fernando Valley and southbound onto the 5 Freeway.
The southbound 5 was still shut down late Tuesday night but reopened shortly before 1 a.m. Wednesday.