K120 / K120F / K121 / K121F CVT  K121 / K121F CONTINUOUSLY VARIABLE TRANSAXLE SYSTEM  CHECK FOR INTERMITTENT PROBLEMS  

Troubleshoot malfunctions with the ECM in check mode. Intermittent problems are easier to detect with the GTS when the ECM is in check mode. In check mode, the ECM uses 1-trip detection logic, which is more sensitive to malfunctions than normal mode (default), which uses 2-trip detection logic.