This paper presents a robust and effcient detection algorithm for MIMO wireless systems. Theproposed scheme employs a novel combination of bitlevel signal representation, MMSE-preprocessing and Malgorithm. The proposed bit-level algorithm exploits thestructure of the QAM constellation by separating eachbit of the signal to reduce the associated complexity ofthe listing and metric updating steps. In the joint detection/decoding systems, the proposed scheme visits lessnumber of nodes by exploiting the extrinsic informationobtained by the decoder. Our scheme may be employed inthe rank-deficient system. Simulation results demonstratethat the bit-level detector achieves almost the same performance as the existing M-algorithm and it achieves a moresignificant gain in terms of complexity reduction.