Circuit Description
The UART serial data line allows information to be exchanged from module
to module as needed. The UART system is a master/slave arrangement with
the PCM as the Master. The PCM requests and sends the information that
is transmitted on the UART line.
Conditions for Setting the DTC
A check takes place in the PCM as to whether a message is received by
the PCM from the EBCM every 100 milliseconds. DTC U1304 can be set anytime
the ignition is in the RUN position and the PCM does not receive a
message from the EBCM in over 5.6 seconds.
The DTC 1304 is retrieved from the PCM when the PCM is checked for class
2 DTCs. The PCM sets this DTC to inform of a problem on the UART communications
circuit.
Conditions for Running the DTC
The PCM does not receive a message from the EBCM in over 5.6 seconds.
Action Taken When the DTC Sets
| • | The traction control system (TCS) is disabled. |
| • | The amber TCS indicator, in the instrument cluster, is turned
ON. |
Conditions for Clearing the DTC
| • | The condition responsible for setting the DTC no longer exists. |
| • | The ignition switch is turned OFF. |
| • | 100 ignition cycles pass with no DTCs detected. |
Diagnostic Aids
| • | An intermittent condition is likely to be caused by a short to
ground or voltage on the UART data line circuit. Use the Scan Tool Does
Not Communicate with UART Data Line procedure in order to isolate
an intermittent condition. Refer to
Scan Tool Does Not Communicate with UART Data Line
. |
