Diagnostic System Check - Body Control Module (SBM)

DIAGNOSTIC SYSTEM CHECK - BODY CONTROL SYSTEM (SBM)












CIRCUIT DESCRIPTION
The SBM Diagnostic Check is an organized approach to identify problems associated with the SBM. This check must be the starting point for any SBM complaint, and will direct you to the next logical step in diagnosing the complaint. The SBM is very reliable component and is not likely the cause of the malfunction. Most system complaints are linked to faulty wiring and connectors, and occasionally to components. Understanding the computer system and using the tables correctly will reduce diagnostic time and prevent unnecessary parts replacement.

DIAGNOSTIC AIDS
The following conditions may result in an intermittent operation of the SBM with no DTC stored:
^ Any condition which results in the interruption of power to the SBM.
^ Out of range battery or ignition voltage specification. Normal battery or ignition voltage: 9-16V.
^ A loose or damaged ground(s).
^ An open or shorted serial data line.

An intermittent failure in the electronic system may be very difficult to detect and to accurately diagnose. The SBM tests for different malfunctions under different vehicle conditions. For this reason, a thorough test drive is often needed in order to repeat a fault condition. If the system malfunction is not repeated during the test drive, a good description of the complaint may be very useful in locating an intermittent fault condition. Faulty electrical connections or wiring causes most intermitting problems. When an intermitting condition is suspected. check the suspected circuits for the following conditions:
^ Poor mating of connector halves or backed out terminals.
^ Improperly formed or damaged terminals.
^ Wire chafing.
^ Poor wire to terminal connections.
^ Dirty or corroded terminals.
^ Damage to connector bodies.

Use J 35616-A whenever a diagnostic procedure requests probing or checking a terminal. Using this adapter will ensure that no damage to the terminal will occur and will give an idea of whether contact tension is sufficient.

If the DTC is a history DTC, the problem may be intermittent. Perform the tests shown while moving related wiring and connectors. This can often cause the malfunction to occur. Perform a thorough inspection of all related wiring and connectors pertaining to the history DTC stored. Intermittents and Poor Connections

Exit all scan tool tests before cycling the ignition OFF to ON unless the scan tool instructions direct otherwise. Follow the operating instructions in the scan tool operator's manual. Failure to follow these instructions may set DTCs, cause vehicle system malfunctions, set false DTCs, or cause scan tool malfunctions.