No, enter your information as-is. The only items that should be entered in box 12 in Turbotax are items that are written in box 12 in your W-2. the letter codes next to the items are very specific and you can wreck your tax return by entering items that don't belong.
You don't get a separate tax deduction for money that was deducted for a pension plan. The contributions were probably taken from your check pre-tax, but even if not, they aren't deductible on your tax return.
You may be eligible to make tax-deductible contributions to an IRA, depending on your income and other tax situations. But an IRA is a private account you set up with a bank or investment company, it is not the same as a workplace retirement plan or pension, even though they have a similar purpose.
