The weather was good, visibility excellent and the time to react ample.

But Renes didn't slow down fast enough to avoid slamming into the back of that truck on December 9, 2013.

Despite having a mobile phone in his hand at the time, he also didn't call triple-0 as his former partner screamed in pain, her body pinned inside the vehicle.

Renes was sentenced to four months' jail in Port Kembla Local Court on Thursday after pleading guilty to two charges stemming from the crash - negligent driving occasioning grievous bodily harm and failing to stop and assist.

His former partner suffered serious facial and leg injuries in the crash which required surgery, forcing her to spend six weeks in hospital unable to walk.

The court heard the woman screamed for Renes to call emergency services in the moments after impact.

But he didn't, instead members of the public who were trying to assist had to make the call, the court heard.

"They are basically trying to render assistance to her and you don't even call triple-0," Magistrate Geraldine Beattie said in court on Thursday.

"It would have been traumatic to go through all of that as well as being pinned in the vehicle not knowing, as we see in the movies, whether the car was going to explode into flames."

Police prosecutor Aaron Wunderlich said a pre-sentence report showed Renes failed to take responsibility for the crash and "does not seem to have insight into his actions", trying instead to blame the victim.

Defence lawyer Nerissa Keay said her client was upset that he had caused the woman's injuries and accepted that he was at fault.

Magistrate Beattie sentenced Renes to a total of seven months' jail, with four months to be spent behind bars and three on parole, and disqualified him from driving for 30 months.

She said Renes had been deemed unsuitable for community service.

Renes lodged an all-grounds appeal and will return to court on Friday.