A challenge of automotive enterprises is to achieve a total implementation of Lean Thinking tools through the manufacturing processes. The Automotive Cluster of Nuevo Leon (CLAUT) in Mexico developed an instrument which evaluates the use of 23 tools distributed in five levels and 279 criterions to measure the maturity level of its member companies in the implementation of Lean Manufacturing tools. The instrument was made with the collaboration of three companies. This study has the objective to prove, redesign, and standardize this instrument by conducting three rounds of audits with external auditors to a case study in seven companies (OEM, Tier1, and Tier2). The main goal is to decrease the time of evaluation and to standardize it for it to be replicable in different companies of the same industry. The methodology selected was the PDCA cycle, and it was replicated twice. The redesign of the instrument was supported on a theoretical basis, using state of the art as BPM Maturity Model and Lean Enterprise Self-Assessment Tool (LESAT). The results of the audits allow to identify the practical implication of the assessment, and after two cycles led to the improvement of both the application method and the content of the instrument.