Diagnostic System Check

Body Control Module Diagnostic System Check:

CIRCUIT DESCRIPTION
The Module Diagnostic Check is an organized approach to identify problems associated with the module. This check must be the starting point for any module complaint, and will direct you to the next logical step in diagnosing the complaint. The module is a 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 module with no DTC stored:
- Any condition which results in the interruption of power to the module
- Out of range battery or ignition voltage
Specification
Normal module operating voltage: 9.0-16.0 V
- 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 module tests for different malfunctions under different vehicle conditions. For this reason, a thorough test drive is often needed in order to repeat a malfunction. 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 malfunction. Faulty electrical connections or wiring causes most intermitting problems. When an intermittent 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 the 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.
^ Exit all scan tool tests before cycling the ignition from RUN to OFF unless the scan tool instructions direct otherwise. Follow the operating instructions in the scan tool operator's manual. Failure to follow these instruction may set DTCs, cause vehicle system malfunctions, set false DTCs, or cause scan tool malfunctions.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table:
1. This test determines if communication can be established with the module.
2. This test checks for stored module DTCs.
3. This test checks for stored module Loss of Class 2 Serial Data Communication DTCs.
4. This test determines whether communication can be established with other modules connected to the Class 2 serial data line.
5. This test checks for any open module power fuses.
6. This test checks the module power circuit. If the test light does not turn ON, there is an open in the module power circuit.
7. This test checks the module ground circuit. If the test light does not turn ON, there is an open in the module power circuit.