Notes on Fault Code Diagnosis

Manufacturers information on what conditions cause fault codes to set is not specific for all codes. For this reason, some of the examples are used only to illustrate what kinds of conditions to look for when certain codes are present. For all codes, complete testing of the device and circuit indicated by a fault code will lead to solving the problem if the problem is in that circuit. Some devices share their signals with more than one control unit (i.e. auto trans control unit; cruise control/shift lock control unit; ABS control unit; board computer for instrument panel). If testing a device and circuit indicated by a code does not reveal any problems, check wiring diagrams and perform testing on all connected circuits. The fault may be in a circuit connected in parallel to the one indicated by the code.