When a 403(b) plan has an employer contribution added, does the pension codes in Section 8 need to be changed. I have always used 2L, but this plan has never had Employer contributions until now.

I believe you are refering to the instructions for the 5500:

1. 403(b) Arrangements: A pension plan or arrangement using a tax deferred annuity arrangement under the Code section 403(b)(1) and/or a custodial account for regulated investment company stock under Code section 403(b)(7) as the sole funding vehicle for providing pension benefits need only form 5500, Part I and Part II, lines 1 through 5, and 8 (enter pension code feature code 2L, 2m or both).

2L is a 403(b)1 annuity
2M is a 403(b)7 custodial mutual fund

So unless there was a change in the investments for the 403(b), there is no need to change section 8.

for more info see:
http://www.irs.gov/pub/irs-pdf/i5500.pdf