As the networks kick their fall TV marketing efforts into high gear post-Labor Day, they’ve got their work cut out for them. 

Just two new series — the dusted-off franchises “Knight Rider” and “90210” — are registering much awareness so far among TV auds.

Last year at this time, at least 10 freshman skeins had already scored more than 20% awareness among auds. But this year, just six new entries are so far hitting that benchmark, according to the latest fall tracking reports.

TV auds are more clued into NBC’s “Knight Rider” than any other new show so far. More than 60% of viewers are aware that the action series is zooming back into primetime — perhaps no surprise, given the talking car franchise’s place in pop culture history.

Close behind — at just under 60% — is the CW’s “90210.” 

Given CW’s ratings woes, the netlet picked up “90210” partly because of its built-in awareness. And indeed, it has been able to take full advantage of the “90210’s” lasting 1990s legacy (not to mention fascination over which former cast members are returning).

With no similar history to fall back on, the rest of this fall’s new series don’t even come close to matching that pair’s awareness. 

NBC’s new laffer “Kath & Kim” is familiar to about 25% of TV auds, while CBS’ “The Mentalist,” NBC’s “My Own Worst Enemy” and ABC’s “Opportunity Knocks” hover at 21%. Everything else, at least as of late August, was below 20%.

The Beijing Summer Olympics may be partly to blame for the weak awareness numbers so far, as the two-week event appeared to both blunt the promos of rival nets and give NBC fare a slight boost (Daily Variety, Aug. 26). 

Another summer of weak broadcast ratings is also to blame, as the nets are forced to promote to a smaller circulation of viewers. It’s no wonder TV execs keep revisiting old titles: When it’s tough to break through the clutter from cable, the Internet and other sources, at least “Knight Rider” and “90210” came with a built-in awareness.

But before the folks behind “Knight Rider” and “90210” get too excited, it’s worth noting that last year at this time, the Peacock’s “Bionic Woman” redux led all awareness studies — thanks again to the original series’ enduring impact. “Bionic” quickly fizzled after its launch. (Similarly in 2000, the heralded “The Fugitive” — another quick flop — topped the chart.)

And while various controversies juiced awareness last year for CBS’ reality skein “Kid Nation” and ABC’s laffer “Cavemen,” those two series bit the dust.

Network execs have to take awareness studies with a grain of salt: They’re worth measuring whether audiences are dissecting your marketing message — but aren’t a good gauge of whether auds will actually show up. So many factors can skew those numbers that their usefulness is open to debate.

That’s where the “intent to view” measurement comes in. Awareness of Fox’s “Fringe” may still be low, but among those viewers who’ve heard of the show, “intent to view” is high — a testament, perhaps, to sci-fi devotees and fans of exec producer J.J. Abrams.

Among viewers aware that “Fringe” exists, a solid 52% say they’re “definitely” or “more than likely” planning on tuning in. Just below “Fringe,” a full 45%  of auds familiar with CBS’ Simon Baker entry “The Mentalist” said they planned to check it out, while “My Own Worst Enemy” was next, with 37%.

Last month NBC Agency topper Jon Miller told Variety that he’s usually happy if, by launch, at least 40% of the viewing audience is aware of a show and 40% of that crowd intends to view said show — meaning at least 16% of the TV aud will likely tune in. At 62% awareness and 34% intent to view, “Knight Rider” actually comes closest to that goal of any fall show.