The 25-year-old, man-of-the-match after taking nine wickets in England's first test victory last week, has a hip injury.
"We'll only know for sure on the morning of the match if he will be fit to play or not," England captain Michael Vaughan told reporters after a practice session on Tuesday.
England will play Richard Johnson or uncapped Martin Saggers if Harmison is declared unfit.
Harmison and his opening bowling partner Matthew Hoggard were England's main weapons in the first Test, grabbing 16 wickets to stop Bangladesh pushing for a shock win.
Bangladesh, who held a 153-run lead with four wickets in hand, were dismissed for just 10 more runs before England's batsmen easily knocked off the 164 they needed for victory.
"We showed our true batting form only in the second innings at Dhaka," said Vaughan, who made an unbeaten 81 to guide his side to their target.
But Bangladesh remain optimistic despite their seven-wicket defeat.
The hosts, who have lost 24 of 25 matches since getting Test status three years ago, are desperate for their maiden win and captain Khaled Mahmud believes they could spring a surprise on Chittagong's placid wicket.
"It's possible to beat England," Mahmud said. "We have a lot of self-belief going into the match. We're improving in every department day by day."
Bangladeshi spinners Mohammad Rafique and debutant Enamul Haque Junior had the English batsmen in trouble at Dhaka.
The 33-year-old Rafique, with 31 wickets in seven Tests including a best of six for 77 against South Africa, caused particular problems with his deceptive arm ball.
"Rafique will be very important for us," Mahmud said. "But he is not our only weapon. We want the pacemen to chip in too."
The port city of Chittagong, which usually gets abundant monsoon rains from June to August, experienced a heavy shower on Tuesday morning, making the weather an important factor in the match.
"We could not utilise the pitch in Dhaka because of rain," Mahmud said, referring to the first day when only 15 overs were possible.
"That spoilt our chances of getting a big total on the board. Hopefully, nothing like that will happen here."
The second test will be followed by a three-match one-day international series.
Teams (from):
England - Michael Vaughan (captain), Gareth Batty, Mark Butcher, Rikki Clarke, Paul Collingwood, Ashley Giles, Steve Harmison, Nasser Hussain, Matthew Hoggard, Geraint Jones, Chris Read, Marcus Trescothick, Graham Thorpe, Richard Johnson, Martin Saggers.
Bangladesh - Khaled Mahmud (captain), Javed Omar, Rajin Saleh, Mohammad Moniruzzaman, Hannan Sarkar, Mushfiqur Rahman, Habibul Bashar, Alok Kapali, Mohammad Rafique, Tapash Baisya, Khaled Mashud, Mashrafe Mortaza, Enamul Haque Junior.
