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 MANUALSCHEVROLET2002EXPRESS 1 TON VAN V8-8.1L VIN GREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSINFORMATION BUSDESCRIPTION AND OPERATIONDATA LINK COMMUNICATIONS
2002 Chevrolet Express 1 Ton Van V8-8.1L VIN G
Data Link Communications
2002 Chevrolet Express 1 Ton Van V8-8.1L VIN GSECTION Data Link Communications
[1][2]DATA LINK COMMUNICATIONS CIRCUIT DESCRIPTION AND OPERATION
The Class 2 serial data link allows modules to transmit, receive, or exchange data.
^ The Electronic Brake Control Module (EBCM)
^ The Powertrain Control Module (PCM)
^ The radio (IRC)
^ The Vehicle Theft Deterrent (VTD)
^ The Vehicle Immobilizer Module (VIM)
^ The Inflatable Restraint Sensing and Diagnostic Module (SDM)
CIRCUIT DESCRIPTION
Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. In addition to this, Node Alive messages are transmitted by each module on the class 2 serial data circuit about once every 2 seconds. When the module detects the class 2 serial data circuit shorted, the setting of all other class 2 serial communication DTCs is inhibited and a U1300, U1301, or a U1305 DTC will set.
UNIVERSAL ASYNCHRONOUS TRANSMITTER RECEIVER (UART) DATA LINE
Circuit 799 exists pin 12 of the DLC, and is a dedicated communication link between the EBCM and the scan tool. When a communication failure exists with the EBCM, this circuit should be checked. This UART circuit can exist alone, or in conjunction with class 2 serial data communication information, depending on the vehicle, functions/RPOs.
The Class 2 serial data link allows modules to transmit, receive, or exchange data.
^ The Electronic Brake Control Module (EBCM)
^ The Powertrain Control Module (PCM)
^ The radio (IRC)
^ The Vehicle Theft Deterrent (VTD)
^ The Vehicle Immobilizer Module (VIM)
^ The Inflatable Restraint Sensing and Diagnostic Module (SDM)
CIRCUIT DESCRIPTION
Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. In addition to this, Node Alive messages are transmitted by each module on the class 2 serial data circuit about once every 2 seconds. When the module detects the class 2 serial data circuit shorted, the setting of all other class 2 serial communication DTCs is inhibited and a U1300, U1301, or a U1305 DTC will set.
UNIVERSAL ASYNCHRONOUS TRANSMITTER RECEIVER (UART) DATA LINE
Circuit 799 exists pin 12 of the DLC, and is a dedicated communication link between the EBCM and the scan tool. When a communication failure exists with the EBCM, this circuit should be checked. This UART circuit can exist alone, or in conjunction with class 2 serial data communication information, depending on the vehicle, functions/RPOs.
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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.