Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSSATURN2002SL1 L4-1.9L SOHC VIN 8REPAIR AND DIAGNOSISBODY AND FRAMEBODY CONTROL SYSTEMSBODY CONTROL MODULEDESCRIPTION AND OPERATIONCOMMUNICATIONS
2002 Saturn SL1 L4-1.9L SOHC VIN 8
Communications
2002 Saturn SL1 L4-1.9L SOHC VIN 8SECTION Communications
CIRCUIT CHART
Circuit assignments for the Body Control Module (BCM) relating to communications:
CLASS II COMMUNICATIONS
The class II serial data circuit 1807 is used to communicate information between modules (for example the body control module and the engine controller).
Contained in each module's memory is a list of serial data messages that are important and should be received by the module. Also contained are the default actions to be taken by the module, if one of the important messages is not received in time. One of those important messages is the State Of Health (SOH) message. This message is sent by a module (if no other message needs to be sent) to let all the other modules on the serial data circuit know the sending module is working correctly.
Each time the ignition is turned ON, all the modules on the class II serial data circuit first learn the other modules connected to the class II serial data circuit. Modules are able to learn the other modules on the serial data circuit because each of the important messages has a source identifier as part of the message.
This process of learning by a module allows the module to know if it has lost communication with a specific module on the class II data circuit.
Circuit Chart:
Circuit assignments for the Body Control Module (BCM) relating to communications:
CLASS II COMMUNICATIONS
The class II serial data circuit 1807 is used to communicate information between modules (for example the body control module and the engine controller).
Contained in each module's memory is a list of serial data messages that are important and should be received by the module. Also contained are the default actions to be taken by the module, if one of the important messages is not received in time. One of those important messages is the State Of Health (SOH) message. This message is sent by a module (if no other message needs to be sent) to let all the other modules on the serial data circuit know the sending module is working correctly.
Each time the ignition is turned ON, all the modules on the class II serial data circuit first learn the other modules connected to the class II serial data circuit. Modules are able to learn the other modules on the serial data circuit because each of the important messages has a source identifier as part of the message.
This process of learning by a module allows the module to know if it has lost communication with a specific module on the class II data circuit.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.