U Code Charts

CIRCUIT DESCRIPTION
The UART serial data line allows information to be exchanged from module to module as needed. This is done by the Powertrain Control Module (PCM), the PCM requests and sends all the information that is transmitted on the UART line.

CONDITIONS FOR SETTING THE DTC
DTC U1304 can be set anytime the ignition is in the RUN position and the Electronic Brake and Traction Control Module (EBTCM) does not receive a $90 message from the PCM for 6 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ A malfunction Diagnostic Trouble Code (DTC) stores.
^ The Traction Control System (TCS) is disabled.
^ The amber TCS indicator 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
^ It is very important that a thorough inspection of the wiring and connectors be performed. Failure to carefully and fully inspect wiring and connectors may result in misdiagnosis, causing part replacement with reappearance of the malfunction.
^ Thoroughly inspect any circuitry that may be causing the complaint for the following conditions:
- Backed out terminals
- Improper mating
- Broken locks
- Improperly formed or damaged terminals
- Poor terminal-to-wiring connections
- Physical damage to the wiring harness

^ The following conditions may cause an intermittent malfunction:
- A poor connection
- Rubbed-through wire insulation
- A broken wire inside the insulation





TEST DESCRIPTION
The number(s) below refer to the step number(s) on the diagnostic table.
2. This step checks for a short to ground in CKT 800.
4. This step checks for a short to battery voltage in CKT 800.
6. This step checks for an open in CKT 800.