GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 TrailBlazer - 2WD 🢒 DTC 🢒 DTC B1327

Circuit Description

All vehicle modules monitor system voltage. The system voltage message is sent to other modules via Class 2 message. When the system voltage drops below the specified range DTC B1327 shall set within the affected module.

Conditions for Running the DTC

This DTC shall run only if the module has power, ground and the ignition is not in START mode. This DTC shall execute regardless of the battery voltage, except when the DTC B1390 is set current.

Conditions for Setting the DTC
    • This DTC shall be set as current when the voltage falls below 9.0 volts for 1.2 seconds.
    • When the vehicle exits START the module shall delay checking the voltage for 2 seconds.

Action Taken When the DTC Sets
    • A message shall be sent out on the class 2 lines to notify all other modules of low battery voltage.
    • The modules disable the setting of U codes and other DTCs.

Conditions for Clearing the DTC
    • The DTC will clear current status when the voltage is greater than 9.5 volts for 1.2 seconds.
    • A history DTC will clear after 50 consecutive ignition cycles if the condition for the malfunction is no longer present.
    • Use the ON-Board clearing DTCs feature.
    • Use a scan tool.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Tests for the proper voltage at battery positive voltage sense circuit of the module, if voltage is not within the proper operating range, the voltage sense circuit needs to be tested.

    2.

  2. Tests the circuit for high resistance.

    3.

  3. Tests for the proper ground circuit for the module.

Step

Action

Value(s)

Yes

No

Schematic Reference: Starting and Charging Schematics or Power Distribution Schematics in Wiring Systems

Connector End View Reference: Master Electrical Component List in Wiring Systems

1

Did you perform the Engine Electrical Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Engine Electrical

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the battery voltage parameter in the affected module data list. Or with a DMM, measure the battery voltage at the appropriate circuit of the module.

Does the voltage measure greater than the specified value?

9.4 V

Go to Step 6

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the harness connector of the module setting the DTC B1327.
  3. Measure the voltage between the battery positive voltage circuit of the module setting the DTC B1327 and the ground circuit of the module setting the DTC B1327.

Does the voltage measure greater than the specified value?

9.4 V

Go to Step 6

Go to Step 4

4

Test the batter positive voltage circuit of the module setting the code for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 8

Go to Step 5

5

Test the ground sense circuit of the module setting the code for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 8

Go to Step 6

6

Inspect for poor connections at the harness connector of the module setting the DTC. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 8

Go to Step 7

7

Important: Perform the setup procedure for the module setting the code, if necessary.

Replace the module setting the DTC. Refer to Control Module References in Body Control System.

Did you complete the replacement?

--

Go to Step 8

--

8
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK