Service engine light

Hope someone can help I have had my s-10 1999 in several times to get this light out the o2 sensors were replaced it stayed off for 2 weeks and cane back on. they replaced a faulty 02 sensor then it was off for a couple of days. back on again they want to flash something in the computer this is all being done free to try and fix the problem.gas cap is brand new also. the shop will be fixing a leaky intake manifold gasget. this is above one o2 sensor could coolant be dripping on this and causing the problem. any suggestions would be appreciated.

Post the OBD-II codes.