Yesterday I replaced bad MAF on W124 E 220(M111.960) to fix rough idle, now I see HFM code 77, this particular model has O2 sensor and does not have CO potentiometer.

What could be the issue? is it the side effect of bad MAF? I tried clearing the code several times, but it keeps coming back.

P.S: Rough Idle and DTC 10 is fixed after MAF replacement.

Thank You