Circuit Description
The UART serial data line allows information to be exchanged from module
to module as needed. This is done by the PCM, 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 EBCM as to whether a message is received
by the EBCM from the PCM every 100 milliseconds. DTC U1304 can be
set anytime the ignition is in the RUN position and the EBCM does not receive
a message from the PCM in over 5.6 seconds.
Conditions for Running the DTC
The EBCM does not receive a message from the PCM in over
5.6 seconds.
Action Taken When the DTC Sets
| • | 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
and the scan tool Clear DTCs function is used. |
| • | 100 ignition cycles pass with no DTC(s) 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
. |
