DTC U1304 Lost Communication with UART System. Pontiac Grand Prix 2000

For 1990-2009 cars only

Makes 🢒 Pontiac 🢒 2000 🢒 Grand Prix 🢒 Engine 🢒 Engine Controls - 3.1L (LG8) 🢒 DTC U1304 Lost Communication with UART System

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

•	A DTC U1304 is stored.

•	The 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 and the scan tool Clear DTCs function is used.

•	100 ignition cycles pass with no DTC(s) detected.

Diagnostic Aids

•	This DTC cannot be retrieved with a current status. The diagnosis of U1304 is accomplished via the symptom, Scan Tool Does Not Communicate with a UART data line. Refer to Scan Tool Does Not Communicate with UART Data Line .

•	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 .