GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 1999 🢒 Century (China) (CNG) 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC U1301 Class 2 Short to Battery

Object Number: 502360 Size: MF

Circuit Description

Class 2 control modules interface with each other through the class 2 serial data link.

Conditions for Setting the DTC

Class 2 control modules detect a short to B+ in the class 2 serial data link.

Action Taken When the DTC Sets
    • The SERVICE VEHICLE SOON indicator lamp turns on.
    • Class 2 control modules store DTC U1301 in memory.

Conditions for Clearing the DTC
    • Class 2 control modules no longer detect a short to B+ in the class 2 serial data link.
    • Class 2 control modules monitor their own transmitted message over the class 2 serial data link.
    • Using a scan tool.

Diagnostic Aids
    • DTC U1301 indicates that the class 2 serial data link has been shorted to B+. The class 2 control modules send DTC information to a scan tool via the class 2 serial data link. If the class 2 serial data link is currently shorted to B+, the scan tool will be unable to communicate with any class 2 control module. Therefore, you will be unable to obtain a DTC U1301 as a current DTC. However, if the scan tool is able to communicate with a class 2 control module and DTC U1301 is read, it will be a history DTC. Wiggle wires and connectors when performing circuit checks on the class 2 serial data link. This can often cause the short to B+ to reappear.
    • The following conditions may cause an intermittent malfunction to occur:
       - An intermittent short to B+ in the class 2 serial data link.
       - A class 2 control module is shorted to B+ internally.
    • DTC P1626 will set in the Powertrain Control Module (PCM) when the ignition switch is on with the Body Control Module (BCM) disconnected. When BCM diagnostics and repairs are completed, refer to OBD System Check in Engine Controls for additional information on PCM related DTCs.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step determines whether the malfunction is intermittent or the module setting this DTC is faulty.

Step

Action

Value(s)

Yes

No

1

Was the Data Link Connector system check performed?

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Go to Step 2

Go to Diagnostic System Check - Data Link Communications

2

  1. Turn the ignition switch on.
  2. Using scan tool, clear DTCs.
  3. Using scan tool, check for DTCs.

Does this DTC reset?

--

Go to Step 3

Go to Step 4

3

The class 2 serial data link is not shorted. However, the module setting this DTC is malfunctioning. For further diagnosis and repair, refer to:

    • A Powertrain On Board Diagnostic (OBD) System Check in Engine Controls 3.0
    •  Diagnostic System Check - ABS in Antilock Brake System.
    • Instrument Cluster System Check in Instrument Panel, Gauges and Console
    •  Scan Tool Diagnostics in Body Control System.
    •  SIR Diagnostic System Check in SIR.

Is the action complete?

--

Go to Step 5

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4

The malfunction is not present at this time. Refer to Diagnostic Aids for additional information regarding this DTC.

--

--

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5
  1. Turn the ignition switch off.
  2. Reinstall connectors/components removed and verify repairs.

Is the action complete?

--

System OK

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