Conditions for Setting the DTCs
- No valid messages are detected on the class 2 serial data circuit.
- The voltage level detected on the class 2 serial data circuit is in one of the following conditions: High Low
- The above conditions are met for approximately 3 seconds.
Action Taken When the DTCs Sets
The module uses default values for all parameters received on the class 2 serial data circuit and all other DTCs are inhibited.
Intermittent
Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Data Link References
This table identifies which serial data link that a particular module uses for in-vehicle data transmission. Some modules may use more than one data link to communicate. Some modules may have multiple communication circuits passing through them without actively communicating on that data link. Additionally, these modules may utilize communication circuits not accessible from the data link connector (DLC), use the schematic reference link in the table for additional information. This table is used to assist in correcting a communication malfunction. For the description and operation of these serial data communication circuits refer to Data Link Communications Description and Operation
| Control Module | Data Link Type | Diagnostic Procedure |
|---|---|---|
| Schematic Reference: Data Link Connector (DLC) Schematics (A/T) or Data Link Connector (DLC) Schematics (M/T) | ||
| Body Control Module (BCM) | Class 2 | Refer to Scan Tool Does Not Communicate with Class 2 Device |
| Digital Radio Receiver | Low Speed GMLAN | Refer to Scan Tool Does Not Communicate with Low Speed GMLAN Device |
| Electronic Brake Control Module (EBCM) | Keyword Data Line | Refer to Scan Tool Does Not Communicate with Keyword Data Line |
| Engine Control Module (ECM) (L61) | Keyword Data Line | Refer to Scan Tool Does Not Communicate with Keyword Data Line |
| Inflatable Restraint Sensing and Diagnostic Module (SDM) | Class 2 | Refer to Scan Tool Does Not Communicate with Class 2 Device |
| Instrument Panel Cluster (IPC) | Class 2 | Refer to Scan Tool Does Not Communicate with Class 2 Device |
| Power Steering Control Module (PSCM) | Class 2 | Refer to Scan Tool Does Not Communicate with Class 2 Device |
| Powertrain Control Module (PCM) (L66) | Keyword Data Line | Refer to Scan Tool Does Not Communicate with Keyword Data Line |
| Radio | Low Speed GMLAN | Refer to Scan Tool Does Not Communicate with Low Speed GMLAN Device |
| Transmission Control Module (TCM) (L61) | Keyword Data Line | Refer to Scan Tool Does Not Communicate with Keyword Data Line |
| Vehicle Communication Interface Module (VCIM) | Class 2 | Refer to Scan Tool Does Not Communicate with Class 2 Device |
Data Link References
Controller Area Network (CAN)
The controller area network (CAN) serial data line is a high speed serial data bus used to communicate traction information between the electronic brake control module (EBCM), the engine control module (ECM), the body control module (BCM), and the transaxle control module (TCM). Typical data-transmission speeds must be high enough to ensure that the required real-time response is maintained.
The addressing scheme employed with CAN assigns a label to every message, with each message receiving a unique identifier. The identifier classifies the content of the message, such as engine speed.
Each module processes only those messages whose identifiers are stored in the module's acceptance list. This is CAN's form of message filtering.
The identifier labels both the data content and the priority of the message being sent. Each module can begin transmitting its most important data as soon as the bus is unoccupied. When more than one module starts to transmit simultaneously, the message with the highest priority is assigned first access. A module responds to failure to gain access by automatically switching to receive mode. The module then repeats the transmission attempt as soon as the bus is free again.
Keyword 2000 Data Line
The Keyword protocols utilizes a single wire bi-directional data line between the modules and the scan tool. The message structure is a request and response arrangement. Keyword 2000 is used for scan tool diagnostics only. The modules do not exchange data on these systems.
The modules on the Keyword 2000 data line are
- Electronic brake control module (EBCM)
- Engine control module (ECM)
- Transaxle control module (TCM)