Download 1990 Lexus LS 400 Testing Diagnostic Procedure – 1) Before testing transmission, ensure fluid level is correct, shift linkage, throttle cable, neutral switch and idle speed are correctly adjusted. Ensure transfer case linkage and transfer switch (if equipped) are correctly adjusted. Battery must be fully charged for accurate testing. 2) To aid in fault diagnosis, determine if fault is hydraulic, electronic or a combination of both. 3) The electronic control is capable of storing self- diagnostic codes. To determine if a fault is electrical, read any stored diagnostic codes. Repair electrical fault associated with the code. See DIAGNOSTIC CODES. NOTE: Not all electrical faults will cause a diagnostic code to be stored (i.e. throttle position sensor and brake signal). Farther circuit tests may be required See ELECTRICAL COMPONENTS & CIRCUIT.