Regulations and agreements among the automobile manufacturers have resulted
in the data link connector (DLC). This connector must be used for the scan tool and
programming access to all communications systems used for those purposes on the vehicle.
The connector must have the following:
| • | A 16-pin connector configuration to which all scan tools connect |
| • | Scan tool battery power always available at pin 16 |
| • | Scan tool ground always available at pin 4 |
| • | A clean signal ground always available at pin 5 |
The rest of the pins are available for serial data communications to the vehicle
system.
The serial data circuits are the means by which the microprocessor-controlled
modules in the vehicle communicate with each other and the scan tool. There are 3 different
types of protocols on this vehicle:
| • | The universal asynchronous receiver transmitter (UART) |
The scan tool accesses the following module data lines:
| • | The engine control module (ECM), Keyword 2000 |
| • | The transmission control module (TCM), Keyword 2000 |
| • | The theft deterrent control module, immobilizer, Keyword 2000 |
| • | The inflatable restraint sensing and diagnostic module (SDM), UART |
| • | The electronic brake control module (EBCM), Keyword 82 |
| • | The remote control door lock receiver (RCDLR), Keyword 82 |
| • | The speed sensitive power steering (SSPS) module, Keyword 82 |
UART Data Line
UART-based communication systems have a master of the serial data line
and remote transceivers. The master controls the message traffic on the serial data
line by polling all of the remotes, control modules. The master then waits for the
proper response.
| • | The UART serial data line allows the inflatable restraint sensing and
diagnostic module (SDM) to communicate data with a scan tool. |
| • | The UART serial data line allows a scan tool to communicate with this
module for diagnosis and testing. |
Keyword 2000 Data Line
The Keyword protocols utilize a single wire bi-directional data line
between the module 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 Keyword 2000 serial data line allows the following components
to communicate with the scan tool: |
| - | The engine control module (ECM) |
| - | The transmission control module (TCM) |
| - | The theft deterrent control module, immobilizer |
| • | The Keyword 2000 serial data line allows a scan tool to communicate
with these modules for diagnosis and testing. |
Keyword 82 Data Line
The Keyword protocols utilize a single wire bi-directional data line
between the module and the scan tool. The message structure is a request and response
arrangement. Keyword 82 is used for scan tool diagnostics only. The modules
do not exchange data on these systems.
| • | The Keyword 82 serial data lines allows the electronic brake control
module (EBCM), the remote control door lock receiver, and the speed sensitive power
steering (SSPS) module to communicate data with the scan tool. |
| • | The Keyword 82 serial data line allows a scan tool to communicate
with these modules for diagnosis and testing. |
