GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 GMC K Sierra - 4WD 🢒 Body and Accessories 🢒 Body Control System 🢒 DTC B3147 RF Unlock Switch Circuit Low

For a full page schematic, refer to

Cell 51: Uplevel Door Locks


Object Number: 366607 Size: FS
Body Control Module Components
Body Control System Circuit Description
Cell 51: Base Power Door Locks
Cell 51: Passlock Sensor, VSS Signal
Handling ESD Sensitive Parts Notice
Power Distribution Schematics
Power Distribution Schematics
Door Lock/Indicator Schematics
Ground Distribution Schematics
Door Lock/Indicator Schematics
 in Body Control Module Schematics.

Circuit Description

The body control module (BCM) monitors and supplies an output voltage on circuit 194. When the BCM receives a UNLOCK command from the remote control door lock receiver the BCM supplies voltage on circuit 194 to UNLOCK the passenger door.

Conditions for Setting the DTC
    • When the BCM receives a UNLOCK signal to UNLOCK the passenger door from the remote control door lock receiver module and circuit 194 is shorted to ground.
    • The system voltage must be between 9.0 volts and 16.0 volts.
    • The above conditions must be met for 0.25 seconds.

Action Taken When the DTC Sets
    • The UNLOCK system will not UNLOCK the passenger door from the key fob.
    • The door lock switches will not LOCK or UNLOCK the doors.

Conditions for Clearing the MIL/DTC
    • A current DTC will clear after the next fault free passenger door UNLOCK cycle.
    • A history DTC will clear after 100 consecutive ignition cycles without a fault present.
    • History and current DTC(s) can be cleared using a scan tool.

Diagnostic Aids
    • Always diagnose the first DTC listed on the scan tool.
    • The scan tool must display DTC B3147 as a current code before performing diagnostics.
    • Perform a visual check for loose or poor connections at all related components
    • Refer to Intermittents and Poor Connections in Wiring Systems.

Test Description

Step number(s) below refer to the same step number(s) in the Diagnostic Table.

  1. This step determines if the UNLOCK relay is shorted.

  1. This step determines if the LF door lock switch is shorted to ground.

  1. This step determines if the RF door lock switch is shorted to ground.

  1. This step determines if the circuit 194 is shorted to ground.

Step

Action

Value(s)

Yes

No

1

Was the BCM Diagnostic System Check performed?

--

Go to Step 2

Go to Diagnostic System Check - Body Control System

2

  1. Turn the ignition switch to the OFF position.
  2. Remove the UNLOCK relay from the left bussed electrical center (LBEC).
  3. With a scan tool monitor the current DTCs.
  4. Press and release the UNLOCK button twice on the key fob.

Does the Scan tool display B3147 as a current code?

--

Go to Step 3

Go to Step 9

3

  1. Disconnect the LH power door lock switch.
  2. With a scan tool, monitor the current DTCs.
  3. Press and release the UNLOCK button twice on the key fob.

Does the Scan tool display B3147 as a current code?

--

Go to Step 4

Go to Step 7

4

  1. Disconnect the RH power door lock switch.
  2. With a scan tool monitor the current DTCs
  3. Press and release the UNLOCK button twice on the key fob.

Does the Scan tool display B3147 as a current code?

--

Go to Step 5

Go to Step 8

5

  1. Disconnect the brown BCM (C1) connector and remove the combs from the connector.
  2. Connect a test lamp to B+ and backprobe in order to prevent damage to the terminal to CKT 194 (WHT) cavity A3.

Does the test lamp light?

--

Go to Step 6

Go to Step 10

6
  1. Locate and repair the short to ground the in CKT 194 (WHT) between the BCM and the UNLOCK relay and or the LF and RF door lock switches.
  2. Replace the open MIR/LOCK fuse (located in the LBEC).

Is the repair complete?

--

Go to Step 11

--

7
  1. Replace the LH power door lock switch.
  2. Replace the open MIR/LOCK fuse (located in the LBEC).

Is the repair complete?

--

Go to Step 11

--

8
  1. Replace the RH power door lock switch.
  2. Replace the open MIR/LOCK fuse (located in the LBEC).

Is the repair complete?

--

Go to Step 11

--

9
  1. Replace the UNLOCK relay.
  2. Replace the open MIR/LOCK fuse (located in the LBEC).

Is the repair complete?

--

Go to Step 11

--

10
  1. Replace the BCM. Refer to Body Control Module Replacement .
  2. Program the BCM with the proper calibrations. Refer to Body Control Module (BCM) Programming/RPO Configuration .
  3. Perform the learn procedure.

Is the repair complete?

--

System OK

--

11
  1. Re-connect all components.
  2. Clear the DTC(s). Refer to Clearing DTCs

Is the Action complete?

--

System OK

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