Introduction

All diagnosis should begin with the comprehensive visual inspection. Further diagnostics are determined by the type of condition requiring diagnosis. Additional sections include test procedures for No Start conditions, Fault Codes in Memory, No fault Codes in Memory, and Adjustments.

All electrical wiring, connectors, pins and cavities should be carefully inspected throughout the diagnostic procedure for damage, corrosion and poor contact. Vacuum hoses, connections and air passages should also be thoroughly inspected for leaks, restrictions and damage. Component part numbers should be verified to assure correctness for engine and emission certification applications. After repairs are made, the system should be retested to verify that no other repairs are required.

On-Board Diagnostics include fault codes which are retained in ECU memory until cleared. Fault codes are cleared from memory by turning the ignition key to the off position, and then disconnecting the negative battery cable for more than ten seconds. Fault codes should always be cleared using this procedure after repairs are made. It is important to remember that the length of time a fault code has been stored in memory cannot be determined.